FLOTATION OF ZINC SILICATE 3Y N-OCTYL
METHYLENE BLUE

BY
I-IALVERN FRANK OBIiECHT

A THESIS
Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of
DOCTOR OF PHILOSOPHY
Department of Chemical Engineering
19 5 2

FLOTATION OF ZINC SILICATE BY
N-OCTYL METHYLENE BLUE

By
Malvern Frank Ob re cht

AN ABSTRACT
Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of
DOCTOR OF PHILOSOPHY

Department of Chemical Engineering

Approved

FLOTATION OF ZINC SILICATE B Y N-OCTYL
METHYLENE BLUE
ABSTRACT
The application of n-octyl methylene blue as a collec­
tor for the flotation of zinc silicate was investigated.
This study was carried out on three zinc silicate ores,
namely, (1 )

Willemite ZngSiO^, (2 )

Calamine or Hemimor—

phite, Z^COlO^SiO-j or Zn^( QH)2Si2<L, .H^O, (3 )

A commercial

Los Lamentos ore, a tested zinc silicate from Mexico.
The collector was synthesized by preparing a modified
dye which was known to mordant zinc salts.

The inability

to modify methylene blue directly required extensive organic
synthesis, including the preparation of ortho n-octyl dimethyl
aniline which was used to prepare the compound called n— octyl
methylene blue.
The flotation tests were carried out on a feed consist­
ing of from 1/o to G'p zinc with the majority of the gangue
material being silic-ious.
was also investigated.

Reflotation of the concentrate

In both studies, a 100 gram batch

type flotation cell was employed.

Under the test conditions

used it was found that n— octyl methylene blue functions as
a selective collector for zinc flotation.
the concentrate produced an improved cut.

Reflotation of

The modified dye appears to offer a new approach to
the flotation of zinc silicate#

It is theorized that selec­

tivity for zinc silicate of the modified dye is due to the
mordant action of the zinc atoms in the atomic lattice of
the zinc silicate, further, that the zinc silicate particles
are "Enveloped" "by the dye molecules.
It is demonstrated that the factors of pH, particle
size, and the amount of collector affect the percent zinc
in the concentrate, percent recovery of zinc, enrichment of
the product, and the improvement factor in the flotation
of zinc silicate hy n-octyl methylene "blue.

Certain trends

are shown to exist for these factors, and under the condi­
tions of the test "optimums" appear to exist for the zinc
silicate ores studied.
The commercial synthesis of n-octyl methylene blue is
not practical.

However, the approach using this compound

as a collector, is fully justified hy our present knowledge
of dye mordants as well as the presently developed theory
of surface chemistry relative to mineral flotation.

i

A CKNOWLEDGEME NT

jfhe writer expresses his appreciation to Pro­
fessor Clyde C, DeV/itt for his guidance in this
investigation of the flotation of zinc silicate by
the use of alkyl substituted methylene blue.

Many

interested engineers in the mineral flotation field
have given a full measure of encouragement and in­
terested advice in the opening of what promises to
be a confirmation of a new approach to the separa­
tion of heavy metal silicates from their gangue ma­
terials*

ii
Malvern. Frank Obreeht
Candidate for the degree of
Doctor of Philosophy
Final Examination:
Dissertation:

July* 28, 1952, 1:00 P.M., Room 308,
Olds Hall

Flotation of Zinc Silicate "by n-octyl
Methylene Blue.

Outline of Studies
Major Subject: Chemical Engineering
Minor Subject : Metallurgical Engineering
Physical Chemistry
Biographical Items
Born, St. Louis, Missouri
Undergraduate Studies, St. Mary1s College, Winona,
Minn. 1942-43* Washington University, St. Louis,
Mo. B. S. Chemical Engineering 1945.
Graduate Studies, Washington University 1945-46,
University of Detroit M. S. in Physical Chemistry
1947, Michigan State College 1947-52.
Experience: Asst. Chem. St. Mary's College 1942-43*
Lab. Instr* Washington University 1943-45* Chem.
Research and Development Engr. Orchard Paper Co.,
1945-46, Techg. Fellowship University of Detroit
1946, Inst. University of Detroit 1946-47, Lee.
ibid slimmer 1947, Asst. Prof. of Chem. and Metall.
Engrng. Michigan °tate College 1947 to date, Adult
Extension Lee. in Power Field 1949 to date. Con­
sultant 1947 to date. Member: Am. Inst, of
Chem. Engrs., Am. Chem. Soc., Mat. Assoc. Power
Engrs., Am. Inst, of Military Engrs., Am. Inst.
Engr. Ed., E.S.D., Alpha Chi Sigma, Sigma X i ,
Author Engrng. Chemistry of Power Plants and In­
dustrial Water Treatment 1949.

iii
TABLE OF CONTENTS

I

Acknowledgement s.....................
.... . 1
Vita............................................. . ii
iii
Table of Contents..............................
INTRODUCTION........................................1
Object and Scope............. .................... 1
Beneficiation of Oxidized Ores ofZinc...........• 1
Flotation Principles. ..... .... ......... .
3
Collectors.
..... .
9

II

PROCEDURES............................... .......... 18
Important Procedures. • ............... -.......
(a)
(b)
(c)
(d)

13

Flotation Procedure....................... . 18
Test Procedure...................... .
19
Determination of Zinc................
23
Synthesis of Collector.....................28

III

TABULATED RESULTS.......................... ........ 30

IV

DISCUSSION..........................................57
(a)
(b)
(c)
(d)
(e)
(f)
(g)

V

The Collector
..... ............ .
Selective Mordant Action.....................
Flotation of Willemite-Zinc Silicate.........
Flotation of Calamine-Zinc Silicate..........
Flotation of Los Lamentos Zinc Silicate......
Depressants and Activators...... .......
Accuracy and Summary
..... ..........

CONCLUSIONS....................... .............. .

59
62
63
70
76
79
80
82

APPENDIX............................................ 84
Synthesis of n-octyl methylene blue...........
85
Synthesis of n-octyl dimethyl a n i l i n e 91
Gravimetric Determination of Zinc In Zinc Sili­
cate ores........... .......................... 98
PolarogSfflphic Determination of Zinc in Zinc
Silicate ores
......
104
BIBLIOGRAPHY......................................... 106

1

nmtGDucsioN
OBJECT AKD SCOPE
The object of this investigation is the flotation of zinc
silicate ores "by the use of al&yl substituted methylene blue*
The modified dye functions as a collector for various zinc
silicate ores.

Methods for preparation of the modified dyes

are not available in the literature, and therefore the syn­
thesis is reported as a part of this investigation.
ZIl'TC SILICATE PLOTAT IOil
Ores rich in zinc content are relatively scarce in the
United States.

The demands for zinc during World War II empha­

sized the need for a method of recovering zinc in low-grade
zinc silicate ores and tailings from milling operations.
There is a need for a collector which can enrich higher grades
of zinc silicate ores and thus decrease the cost of producing
zinc.
Examination of the literature up to the present indicates
that zinc silicate has never been successfully floated either
in the laboratory or in the field*
BEI'IEEIGATIOE OF OXIDIZED OSES OF ZI1TC
Attention has been given to beneficiation of oxidized zinc
ores by pyrometallurgical means (56).

This type of operation

is more costly than flotation and requires a good grade of zinc
ore.

2
High, grade zinc ores may be beneficiated "by the use of
the metallurgical process of volatilization.

In this process

the ore is decomposed and the zinc vapors mechanically removed
"by an inert gaseous stream.
some ores is 1370°C.

She decomposition temperature for

(^)

Mineral dressing methods such as jigging and tabling pro­
duce little beneficiation of an ore containing hemimorphite,
Z^SiO/j,, and smithsonite, ZnCO^, when the ore is finer than *4-8
mesh.
The Waelz process of volatilization has been reported to
work on oxidized zinc ores with a zinc content of only 6 per
cent.

However, considerable trouble is encountered in the for­

mation of incrustations on the lining of the kilns.

These in­

crustations require complicated operations to remove them; they
also limit the length of the kiln.
Mixtures of quartz gangue and zinc silicate ores, such as
willemite and calamine used in this investigation, could be
separated by the use of a heavy liquid.

The float and 3ihk pro­

ducts of such a process, would probably show a fair separation
(78).

The general method of heavy liquid separation is de­

scribed in the Bureau of Mines Technical Paper Ho. 381.

How­

ever, according to this authority, this method has not proven
practical on the majority of zinc silicate ores.

It becomes

apparent that a solution to the problem of concentrating these

3
oxidized, zinc ores, especially zinc silicate, lay froth flota­
tion, would he a very useful application.
Evidently it is more desirable to float the zinc silicate
away from the gangue because it is in much smaller concentra­
tion and should require less reagent.

However, there may be

some merit in first floating the gangue of a zinc silicate ore
provided the gangue is essentially quartz.

This might be done

lay the use of amine such as Armour's AM-1120.

However, if the

gangue is a mixture of the various silicates with quartz, this
operation is not successful (17)*
Hecent patent literature (5 ^) reveals claims by engineers
of the International Smelting and Refining Company.

They

claim a separation of oxidized zinc ores from lead ores by
froth flotation.

The method used a high concentration of a

soluble sulphide and a soluble salt of certain aliphatic amines.
In this method it appears that there is first, an adsorption
of sulphide.

Subsequent metallurgical results have shown that

the flotation of oxidized minerals is much more successful with
than without sodium sulphide (50).

At the present time there

is available no laboratory or commercial method of concentrat­
ing zinc silicate by froth flotation.
FLOTATION PRINCIPLES (18 , 20 , 25 . 7^)
Flotation is a method of wet concentration of ores in
which the separation of minerals from gangue is effected by

4
causing the mineral to float at the surface of the liquid
pulp while the gangue remains submerged (28).

Since the turn

of the century, rapid progress has been made in the flotation
of certain sulphide ores.

One constantly strives for differ­

ential flotation, i.e., the selective flotation of one particu­
lar metal ore.

In 1902 Proment (37) discovered that bubbles

of gas, when passed through an ore mixture, served as a carrier
for sulphide minerals.

He also discovered that oil helped

the bubbles' carrying properties.

In 1904- Cattermole was

issued a British Patent (10) for a process in which ore, water,
and oil were mixed together in order to secure an emulsion of
the oil.

The emulsified oil coated the sulphide particles

and formed granules which sank.
to overflow.

The tailings were allowed

It should be noted that in early days, large

quantities of reagent were used.

While working on the Catter­

mole Process, Sullman, Picard and Ballot found that by using
only small amounts of reagent, the granules of sulphide ore
floated.

Their patent makes the first mention of a soluble

frothing agent (70).

It was about this time that Hoover (44)

developed the modern flotation cell; this cell, as do the
more modern flotation cells, used mechanical agitation and
compressed air.
The early twenties found much attention being given to
the development of organic reagents for differential flotation

5
of sulphide minerals in ores*

The most noteworthy of these

are the series of alkali organic dithiocarbonates, commonly
known as xanthates, discovered "by Keller and Lewis in 1925 (46),
Xanthates are now successfully used in the flotation of many
non-sulphide minerals.

As early as 1905 Schwarts proposed the

sulphide filming of oxidized minerals by the use of the var­
ious alkali sulphides (66).

The mineral dressing literature

reveals no success of this method when applied to oxidized
mineral of the form of zinc silicate.
Interfaces may exist wherever gases, solids, or liquids
come into contact.
thickness.

A n interface has length, width and minute

It is an elastic film*

The energy connected with

this film is referred to as surface or interfacial energy.
The scientific fundamentals of flotation have their basis in
the work of Gibbs and Helmholtz, Efttvos and van derWaals, on
surface phenomena.

The structure and nature of interfacial

films and the concept of orientation of polar and nonpolar ends
of a molecule forming a film on insoluble substances in water
was first thoroughly explained "by Langrauir in 1916.
FLOTATION KEAGENTS
Flotation reagents may be grouped as frothers, modifiers,
and collectors.

It is desirable in flotation to have a par­

ticular chemical function as only one reagent.

Thus a frother

should only be a frother and not a collector in the same

6
operation.

Mary of the chemical characteristics of frothers

and collectors are the same.

Frequently a collector will

function as its own frother and thus eliminate the need for
the latter reagent.

However, in most commercial flotation

operations all three reagents are used.
FROTHERS (3 , 29 , 36)
Frothers are used to form a stable froth.
by lowering the surface tension of water.

They function

The froth mxat carry

the mineral load to the surface and be stable enough to allow
mechanical removal.

Frothers are usually organic in nature.

One part of the frother molecule is polar, the other nonpolar.
The polar end of the frother is in the water phase at the inner
surface of the air bubble, the nonpolar part of the frother is
in the air interface of the bubble.

Good frothers collect at

the liquid—air-interface of the gas bubble and give the bubble
elasticity*

There is less surface energy at the reagent—air-

water interface than at the reagent—water interface.
contain one of the following radicals:

Frothers

OH (hydroxyl) CO

(carbonyl), COHH2 (amide), COOH (carboxyl), COO (ester) and
COC (ether) (75).

Commercial frothers are pine oils, cresylic

acids and alcohols containing five or more carbon atoms.

The

amount of frother needed depends on the type of ore being
floated.

It is usually less than 0.15 pound per ton of ore.

Mineral particles are attached to bubbles when the surface

7
energy* of the air-solid interface is less than that of the
solution-solid interface.

A tension must exist at the solution-

solid-interface; attachment of the particles to the hubbies
lowers this tension and establishes equilibrium.
MODIFYING- AGENTS
Modifying agents may be classified as pH regulators, clean­
ing agents, activators, depressants, and dispersants.

The same

chemical may function as one agent on one ore and as a differ­
ent agent on another ore.

An activator functions by modifying

the surface of the mineral so that the collector will be
effective.

Most activators produce a sulphide surface on the

ore, either by chemical means as in the case of copper sul­
phate or by absorption as when sodium sulphide is used*

The ma­

jority of the flotation processes require some control of pH.
Soda, lime and caustic soda are used to maintain an alkali cycle.
The choice of pH regulators is governed by the cost.

They

should be of such a nature that they will not depress the flo­
tation of the desired mineral.
Depressants are used to prevent the flotation of the unde­
sirable gangues or a particular mineral.
frequently used in differential flotation.

These reagents are
Many sulphide ores

are depressed (not floated) by the use of strong oxidizing agents, i.e. the bichromates and permanganates.

These oxidizing

agents change the sulphides into basic sulphates, oxides,

8
hydroxides, or thiosulphates.

Alkaline cyanides depress the

flotation of iron sulphide hy reacting with oxidation products
to form a protective film of ferrocyanlde and complex cyanates.
The cyanides also depress flotation in an alkali circuit; in
this case it is believed the protective films are hydroxide.
The chief use of cyanides is in separating galena from zinc aid
iron ores like pyrite, pyrrhotite, sphalerite, and marmutite.
Colloidal materials either from slimes or from organic
starches and glues are known to depress flotation.

This accounts

for the necessity of desliming operations in most flotation
processes.

In the case of organic compounds it is believed

the colloids coat the particles; these coated particles selec­
tively attract v/ater and therefore inhibit their flotation.
The work of Taggart (?l) and associates revealed that the inten­
sity of flotation varies with each reagent and mineral used,
and is an inherent property of the ore and reagent system.

It

is common practice in the separation of two minerals by flota­
tion to attempt to depress the flotation of the one mineral
while the other mineral is floated.

After this, a promoter

reagent is added which destroys the depressant and then the
second mineral is subjected to a flotation operation.

The a-

mount of promoter depends on the ore, and the amount of the
preceding flotation or collector reagent, as well as the opti­
mum pH at which the second mineral may be floated.

9
COLLECTORS
The alkyl substituted methylene "blue, which was used in
this investigation, functions as a collector.

This collector

forms a film or "envelope" around the zinc silicate particles
and makes the particles water repellant.

Methylene "blue was

chosen to form the envelope around the zinc silicate particles
because it was known that zinc salts are mordants for the
ordinary methylene blue dye.

However, (8 , 33» 3^» 38) in order

to have flotation by methylene blue, it is necessary to have
an aliphatic hydrocarbon chain attached to the dye to produce
hydrophilic properties.

Also, in order to have flotation,

the air bubbles in the presence of water, must have a positive
contact angle with the coated particles.

The contact angle

resulting from the displacement of water by air on the coated
zinc silicate particle depends on the nature of the mineral—
water, air-water, and water-air interfaces.
One possible mechanism by which alkyl substituted methy­
lene blue renders the zinc silicate particles water repellent
is as follows:

The polar dye group of the collector is absorbed

by the zinc silicate particles.

This allows for orientation

of the non-polar aliphatic hydrocarbon chain outward from the
particles.

The aliphatic hydrocarbon chains orient themselves

in the air interface of the air bubbles.

The bubbles, with

their mineral load of the zinc silicate particles, rise to the

surface of the flotation cell where they are removed.

It

seems entirely reasonable to say the enveloping or anchoring
of the dye collectors to the zinc silicate occurs for the
same reason that zinc salts, oxides or hydroxides, act as a
mordant for methylene blue in textile dyeing.

That this is

true beyond a reasonable doubt is borne out by data subse­
quently reported.
Alkyl substituted methylene blue is a cationic collector.
Its collecting properties may result from the formation of a
positive organic ion.

The alkyl-substituted methylene blue

positive ion is formed by the loss of a negative chloride ion.
In this mechanism, the negative part of the mineral reacts
with the positive organic ion.

The result, as in the previous

mechanism, is the production of an organic hydrophyllic film
on the surface of the zinc silicate.

Some of the best known

cationic collectors are alkyl amines and quaternary ammonium
compounds.

Whether organic collectors are cationic or anionic

compounds is still a field of much theorizing.

However, either

of these mechanisms give some theoretical mental satisfaction.
DeWitt and Ludt (2h) in their work on alkyl-substituted tri­
phenyl methane dyes discuss many of the factors effecting
cationic flotation.
In cationic flotation, an excess of collector must be
avoided (15).

In some cases, the frother should be added after

the collector to prevent the coating of the particle by the

11
frother (31)» while in other cases, the period of condition­
ing of the ore affects the degree of flotation.
FLOTATION OF ZINC SILICATE OSES
An exhaustive literature survey reveals no direct work
on the flotation of zinc silicate ores.

It did however, dis­

close some investigations on the flotation of oxidized zinc
ores.

Since zinc silicate "belongs to this group of oxidized

zinc ores, it is of engineering interest to trace the approaches
used in these investigations.
She term oxidized zinc ore or mineral includes the
naturally occurring oxygen compounds of zinc such as the
oxides, sulphates, carbonates, hydroxides and silicates.

Oxi­

dized ores have a tendency to hydrate due to the fact that the
oxygen atoms are not completely saturated.

'This hydration

characteristic is not possessed by mineral sulphides.

She.

wettability by water, or hydration, makes flotation difficult.
In general, oxidized ores are only slightly more floatable
than their accompanying gangue materials which are usually
alkaline earth silicates.
The problem of floating oxidized ores is essentially one
of changing the surface of the oxidized ores so they are less,
wettable by water, without making a similar change in the sur­
face properties of their accompanying gangue materials.
this is accomplished, favorable conditions exist for the

"When

12
froth, flotations of the selectively coated particles of the
oxidized ore.
Prior to this work two approaches have "been used in the
investigation reported on flotation of oxidized zinc ores*
The first is the sulphidizing of the oxidized surface and sub­
sequent flotation "by one of the zinc sulphide mineral collectors*
This approach is probably a result of the success obtained in
the differential flotation of zinc sulphide by use of the xan­
thates.

Xanthates have been successfully employed as collectors

for zinc sulphide for many years.

The superficial sulphide

coating makes the ore floatable by ordinary zinc sulphide
collectors*
A n example of this approach (50) is shown in the follow­
ing investigation on oxidized lead-zinc ores containing 6$
lead and 10.5$ zinc.

In this case, the crude ore was given a

batch grind without reagents at 53$ solids to approximately
80$ — 200 mesh.

The pulp was placed in a flotation cell and

diluted to about 25$ solids.

The lead sulphide is floated by

using 0.36 pounds per ton of potassium ethyl xanthate, 0.10
pounds per ton of methyl amyl alcohol, and 0.25 pounds per ton
of potassium pentasol amyl xanthate.

Stage additions of A

pounds per ton of sodium silicate, 5 pounds per ton of sodium
sulphide and 2.5 pounds per ton of potassium pentasol amyl
xanthate and subsequent flotation of the oxidized lead ores.

13
To the lead tailings were added 5*0 pounds of soda ash, 8,0
pounds per ton of sodium sulphide and, .267 pounds per ton
of lauryl amine hydrochloride; a five minute conditioning per­
iod was used with no air in the cell.

Shis first zinc concen­

trate is then removed in ten minutes of flotation.

So the

tailing containing considerable zinc 2 pounds per ton of sodium
sulphide was added and a second zinc concentrate was obtained,
ho tests were run on oxidized zinc ores without first perform­
ing an extensive lead separation,

These ores apparently con­

tained little zinc silicate and appear to be primary to the
other oxidized zinc ores,

desuits reported on zinc silicate

from a silicious gangue were not uniformly good (50 ).
The explanation of the success on the oxidized lead ores
and lack of uniform results on zinc silicate may have its
basis in the work of Peterson (57) on sulphidizing.

With oxi­

dized ores, the negative part of the mineral containing
oxygen may be replaced by sulphur so that the ore is floated
in the same way as the corresponding sulphide.

This ex­

change is only possible when the sulphide forming on the surface of the
oxidizing ore is more difficulty soluble than the corres­
ponding oxidized compounds, while oxidized zinc may not be
sulphidized because zinc sulphide is more soluble than
the oxidized zinc ore.

In a consideration of the solubility

of the sulphide in comparison to the oxidized compound, one

14
one mast always "bear in mind that in the first place, sulphidizing apparently forms an amorphous substance, and in most
cases, an easily soluble sulphide (58)*

It thus appears that

the solution to the problem of flotation of zinc silicate does
not lie in the indicated methods of sulphidizing.
She second approach used in the investigation of flota­
tion of the oxidized zinc ores is in the use of depressants.
The most comprehensive investigation using this approach is
in the recent work of Bunge, line and Legsdin (5)*

This in­

vestigation began with the use of the Rex mine ore which con­
tained smithsonite, zinc carbonate, and hemimorphite or cala­
mine, a zinc silicate.

It was pointed out that pure zinc

carbonate could be floated by either oleic acid or sodium
oleate.

The reaction is believed to be ZnCO^

(C-j^H^COO^Zn + Na^CO^.

ZC^^H^^GOONa

However, these reagents also

float most of the gangue materials associated with the common
zinc carbonate ores.

Attempts were made to suppress the gangue

flotation by the use of starches and dextrins as depressants.
The depressant reagent was prepared by dissolving the
gents in hot caustic solution subsequent to their addition to
the flotation pulp.

Sodium flouride was used to depress the

Iron oxide in the ore thus forming a complex ferric ion.
Commercial starches of different genera contain unknown amounts
of amyloses and unknown carbohydrate constituents.

I’or this

15
reason, starch, was identified only "by its trade name.

The

mechanism of starches and dextrins in flotation is unknown.
Flotation tests were conducted using one pound per ton of
starch or dextrin reagent and 0.3 pounds of sodium oleate
collector.

Three rougher concentrates were taken.

1^0

G-lobe pearl starch, 150 Dextrin, 126 Buffalo starch, 52 hydrol, 185/130 Amijel, 152 Dextrin, 186 Mogul Brand, cereal
hinder, 132 Eagle pearl, were tested.

It was necessary to

perform several cleaning operations on the rougher products.
The ore feed contained 20.3/® zinc.
ed using 152 Dextrin as follows:

Best results were obtain­
The zinc middling contained

23.6$ zinc and the tailings contained 21.9$ zinc.
concentrate contained 21*6$.

The zinc

It is Interesting to note the

conclusions reached by the authors on this ore containing
some zinc silicate.

These conclusions were:

Since the zinc

middlings and the tailings contained a fair amount of zinc
and were low in carbon dioxide, it was concluded that these
products contained the zinc as hemimorphite (zinc silicate),
which apparently was either depressed more permanently by the
conditioning reagents used or did not respond as readily to the
collecting action of the sodium oleate.

It was believed that

more pertinent information on the depressing reagents on
smithsonite or carbonate gangue would be found if the investi­
gation were continued on an ore containing zinc as smithsonite

16
only,

Therefore, the test on the Sex mine ore was discontin­

ued (6 ),

The rest of this investigation was conducted on an

ore which was chiefly zinc carbonate,
Andreeva also reports flotation of smithsonite hy the
preliminary sulfidization at 50-60° followed "by flotation at
room temperature (l),
8-hydroxqunoline (oxine) has been used in conjunction
with terpineol and alkali carbonates or hydroxides in flota­
tion experiments on zinc carbonate with some success (30),
It becomes apparent that these two approaches used in
previous investigations seem to offer little promise in flo­
tation of oxidized zinc ores in the form of silicates.

The

third approach to the flotation of zinc silicate is the develop­
ment of a collector whose nonpolar molecular part is so large
that the hydrophilic action of the zinc silicate is screened
by it.

The 2-8 tetra diaminothiozonium part of the alkyl sub­

stituted methylene blue collector gives a large nonpolar
molecular part.

When this group is attached to a zinc silicate

particle, it should render it hydrophobic.

An aliphatic alkyl

group of sufficient length attached to this nonpolar group
should give the modified dye collecting properties.
The work on the flotation of copper silicate reported by
DeWitt and Ludt (2^) led us to believe that a more general
approach to the flotation of "oxidized ores" was justified.

17
3?or instance, in the process of dyeing, certain inorganic
oxides, or hydrated oxides are precipitated in the textile
fibre*

Shese substances, necessary to the retention of the

dye, subsequently added and adsorbed or reacted with the hy­
drated oxide in the textile fibre, color the cloth*

If the

retention of the dye by the textile fibre Is due to the pre­
sence of the inorganic heavy metal atom, then the dye should,
properly reconstituted, act as an enveloping film on a mineral
having in its atomic lattice the same metallic atoms as are
present in the mordant in the textile fibre as prepared for
successful retention of the dye:
In accord with this theory, already well substantiated
by both theory and practice in the dyeing industry, the pre­
sent ezrperimental work on the flotation of zinc
reported.

silicates is

The results obtained thus far are substantially in

agreement with the work of DeWitt and Ludt (2*0.

In succeeding

data and discussion this point of view will be further develop­
ed and amplified.

18
PROCEDURES
The important experimental procedures are (l)
tests, (2)
(3 )

flotation

determination of zinc in zinc silicate ore, and

synthesis of the alkyl-substituted methylene "blue collec­

tor.
FLOTATION PROCEDURES
The feed to the flotation cell consists of synthetic
mixtures of the zinc silicate ores and sand.
were willemite and calamine.

Zinc ores used

Several cuts of concentrate

and the tailings were analyzed for per cent of zinc.
ores were available only in large pieces.
were passed through a jaw crusher.

These

The large pieces

The product from the jaw

crusher was then subjected to a series of roll crushings
each of finer setting.

This product was then classified in

a series of Tyler screens on a rotap machine.

Ore retained

above the 100 mesh screen is placed in a flint pebble ball
mill and dry ground until it all passes the 100 mesh screen.
Ore finer than 325 mesh was discarded in order to prevent
sliming in the flotation cell.

The ores used were relatively

pure zinc silicate and required little desliming.

The same

size sand and ore were used for various runs.
White sand was wet ground in the ball mill, deslimed
several times and dried in an oven.

The sand was then classi­

fied into the same mesh range as the zinc silicate ore.

19
Flotation feeds were prepared "by taking various amounts
of the high grade ore and mixing with sand of the same mesh
to give a 100 gram sample.

Samples ranging from 1$ to 20$

zinc were used in this investigation.

All samples were oven

dried before weighing.
Tests were run in a 100 gram hatch type flotation cell.
Figures 1 and 2 illustrate the workings of the experimental
subaeration flotation cell.

This type cell has been success­

fully used in recent flotation investigations (1 9 * 21, 22, 23 ,
26, 2?).

These workers used various type ores, feed

mixtures,

reagents, etc. and illustrated the usefulness of the unit.

The

lucite cell held about 250 cc. of liquid and had an air inlet
at the bottom.

The motor driven agitator has its blade direct­

ly over the air inlet at the bottom of the cell.
mechanically swept into a Buchner funnel.
jected to a continuous vacuum.

Froth is

The funnel is sub­

The filtrate was drawn into

a glass bottle.

When sufficient liquid is collected the va­

cuum is broken.

The liquid is then allowed to flow by

gravity into the supply feed bottle.

The supply bottle must

always contain some liquid in order to insure a continuous
feed into the cell.

The rate of liquid feed depends on the

rate at which the froth was removed.
TEST PROCEDURE
Measure out 300 cc. of water, add 70 cc. of this water

20

i&ga

21
V

rr"

I— CELL

2- Cl liI l TIN^ FUNNEL
3- CUMPRE23E > AIR
TLL

BATCu

1-L 'TA :1CN
FIGURE

2

CCL L

22
to the cell.
tation.

Then. add. the 100 grams of ore mixture with agi­

Place a ho. 5 Whatman filter paper in Buchner funnel.

Draw 70 cc. of water through the funnel into the supply "bottle.
Make sure the liquid feed always is closed.
mainder of the water to cell.
ing agents "being employed.

Now add the re­

Adjust the pH and add any modify­

Allow the mixture to condition.

Add all or part of the collector "below the surface again allow­
ing a conditioning time.

A measured amount of frother is used

and the air flow is adjusted*

Water from the supply "bottle

should "be allowed to flow slowly into the cell.

As the froth

forms in the top of the cell, it is manually removed "by a
scraper*

On higher grade feeds remove about 10 grams of

froth concentrate.

A new filter paper is now inserted and a-

nother 10 grams sample taken.

Be sure that the supply "bottle

contains liquid at all times.

Collector can "be added in small

amounts over the period of the run.

The cell is now drained

and a sample of the tailings taken for analysis.

Take the pH

of mixture on Beckman pH meter or with a Taylor slide compara­
tor.

Short range indicating paper can be used during the

course of the run.

The various concentrates and tailing sample

are oven dried at 105-110°C.
zinc content of these samples.
be added during the run.

Record dry weight and determine
If necessary more frother can

In some cases chemicals can be added

during the test to maintain the desired pH.

23
Water used in these flotation tests was either distilled
or Michigan State College well water.

This well water has a

pH value of 7*4, 2-4 ppm. (parts per million) of suspended solids,
a hardness of 333 ppm. as calcium carbonate.

The water is high

in bicarbonate, 382 ppm. HCOj:. It has a total dissolved solid
content of 390 ppm.
ore.

Some feeds were made using once concentrated

This was done because in commercial practice the ores are

subjected to a series of concentration operations.

Several flo­

tation operations are generally necessary to obtain high grade
concentrates and maximum recovery at a minimum cost.
DETERMINATION OP ZINC
Prom a literature survey it became apparent that precise
determination of zinc in a silicate ore is not an easy matter.
The Committee on uniformity in technical analysis show in their
report (9 ) that a sample of oxidized zinc ore from New Jersey
containing willemite, franklinite and zinc spinels, and having
a zinc content of 18.l6> was analyzed by forty-two chemists
with results varying from 12.20 to 39*22/6.

Twenty-three of

the chemists were or had been in zinc works, three in other
works where zinc was frequently determined, eleven were commer­
cial chemists, most of whom made a specialty of zinc, and five
were professors or instructors in college.

They used eight

methods.
The routine method of analysis used in these determina­
tions was an alkaline volumetric solution, an adaptation of

2Mr

procedure given hy Scott (67) and others (32, 64-, 78).

Shis

method was checked hy the gravimetric method of precipitating
the zinc sulphide, converting the zinc sulphide to zinc sulphate,
and weighing the latter,

Shis gravimetric is reported to he

one of the most precise*

She details are given in the appendix.

She three ores used in this investigation as well as
other test samples, were checked hy a polarg§©phic method*
Shis procedure is shown in the appendix*

She apparatus used

was the property of Michigan Health Department.

It cannot he

over emphasized that frequent checks should he made on reagents,
etc* to assure accurate analytical results.
METHOD Or ANALYSIS FOR ZINC
From the foregoing it is apparent that the method of
analysis for zinc, especially in its ores, must he clearly
designated.

She following paragraphs exemplify this.

She

modified alkaline volumetric method used for the analysis of
zinc is for reasons stated ahove, important enough to he
given here in detail.
Weigh b grams of sample into a k-00 cc. heaker, moisten
with water and add 25 cc. HCl (Sp. Gr. 1.20).
on warm plate and evaporate to diyness*

Place heaker

Cool, add 25 cc. water,

25 cc. HCl (Sp. Gr. 1.20) and heat to hoiling and continue
hoiling for 2 minutes.

Cool, transfer to a 250 cc. measuring

flask and dilute exactly to the mark.

Filter (l), catching

4

25
the filtrate in a dry 600 cc. beaker.

Discard the paper and

contents (2).
Measure exactly 125 cc* (3) into the original heaker and
take to dryness on a warm plate.

Cool, add 50 cc. HNO^

(Sp. Gr. 1.42) and bring to a boil (4)*

Add about 5 grams

KCIO^ (5) and boil until solution has a volume of about 20 cc.
Cool, transfer to a 500 cc. measuring flask and dilute to the
mark.

Shake well and filter (6), catching the filtrate in a

dry 600 cc* beaker.

Discard the paper and contents.

Measure exactly 250 cc. (7) into a 600 cc. beaker, add
25 cc. citric acid solution and 5 cc. (S) iron solution.

Neu­

tralize (9 ) with NHjijQH (Sp. Gr. 0.90) and add 3 cc. (10) in
excess.

Bring to a boil and titrate at once with standard

potassium ferrocyanide solution as described under Standardi­
zation.
Calculate the percentage of zinc as follows:
(A - B)

(ff) x 100

- c
p Zinc, where

1
A is the cc. of Kj^FeC CN)g solution required for the sample.
B is the cc. of Kjjpi^CN)^ solution required for the blank de­
termination as described under Standardization.
S’ is the g. of Zn per cc. of KtyE^CN)^ solution.
Notes
(l)

Use a dry No. 1 Whatman qualitative, 15 cm. filter or simi­
lar paper.

Carbon must be removed or the manganese will

26
not "be completely precipitated,
(2)

The carbon may be filtered out and washed free of
chlorides and the insoluble residue used to determine
insoluble zinc after ignition and removing the SiOg
and fusing with KgSgOy,

Insoluble z inc is usually

negligible,
(3)

This is equivalent to 2 grams of the sample,

(h)

Boil until nitrous oxide fumes have disappeared,

(5)

The KCIO^ precipitates the manganese.

It should be add­

ed a little at a time and the watch crystal raised to
permit the yellowish gas to escape.

This gas is explo­

sive.
(6)

Use a dry No. 1 Whatman qualitative, 15 cm. filter or
other paper.

The manganese is filtered off at this

point in the analysis.

The first portion of the fil­

trate should be poured back through, the paper if the
fine precipitate tends to pass through.

The filtrate

must be clear and colorless.
(7)

This is equivalent to 1 gram of the sample.

(8)

The amount of iron to be added depends on the iron in
the sample.

(9 )

The solution should contain about .35 g. Te.

Use litmus paper as the indicator,

(10) The amount of NH^OH in excess required varies with the
per cent of total zinc in the sample.

Tor every 5 cc.

27
of standard, potassium ferrocyanide solution required, an
excess of 3 cc. of

(Sp. Gr. 0.90) is necessary; for

less than 5 cc. the solution should he only slightly
alkaline.
Solutions Required
Citric acid Solution —

Dissolve 350 g. citric acid (C.P.)

in 1000 cc. of distilled water.
Iron Solution —

Dissolve either ferric nitrate or ferric

chloride in distilled water so that 1 cc. contains .035 g. 3P®*
Potassium Perrocyanide —

Dissolve

g. K^Pe(CN)g (C.P.)

in 1000 cc. distilled water and standardize against C.P. zinc.
Age at least 90 days.

See Standardization of Potassium Perro—

cyanide given below.
S 2ANDABDIZAT ION OP POTASSIUM PEBAOCYAN IDE SOLUTION
Weigh .h to .5 g. of Zn (C.P.) (l) into a 600 cc. beaker
and add 50 cc. of water and 10 cc. HNO^ (Sp. Gr. I.h2 ).
and after solution is complete, boil for five minutes.

Cover
Cool,

dilute to 300 cc. and add 25 cc. citric acid solution and 10 cc.
iron solution.

Neutralize with NH^OH (Sp. Gr. O.9 0 ) using

litmus paper and add 30 cc. excess.

Heat to boiling and titrate

immediately with potassium ferrocyanide solution (2).

Make a

blank determination in a similar manner but adding only 3 drops
excess NH^OH.
Calculate the factor as follows:

C
A - B

at

F where,

A

is the cc# of Ki^I'e(C¥)^ solution required for the Zn (C.P,)

B

is the cc. of K ^ e C CH)£ solution required for the Blank.

C

is the weight of Zn in g.

F

is the g. of Zn per cc. of K^PeCClT)^ solution.
Notes

(1)

Zinc Sticks (C.P.) are rolled d.own to about .10“ thick
and the surface is cleaned "by wiping with gasoline
(36° Be*)

(2)

The solution should "be added slowly and stirred vigor­
ously.

The end point is determined "by transferring 3

drops of solution to a spot plate containing acetic acid
(50$).

The end point is indicated "by a change in color

from a yellow to green.

The green is caused "by the

presence of ferric ferrocyanide (Prussian Blue) produced
from ferric ammonium citrate and the slight excess of
potassium ferrocyanide at the end point in the yellow
ferric ammonium citrate,
SYNTHESIS OP COLLECTOR
The exact details of the preparation of n-octyl, 2,8
tetra methyl diaminothiazonium chloride i.e. n—octyl methylene
"blue is given in the appendix.
titles of 1.
2.

It appears there in under the

Preparation of n—octyl methylene "blue, etc.

Preparation of ortho-n-octyl dimethyl aniline.

The reader

29
should refer to Tables A and 3 which gives the complete syn­
thesis of the collector in equation form.

TOTJLA.TKD RESULTS
AMD CURVES

EABL3 I
Selective Mordant Action of n-Octyl Methylene Blue
(Heagent: Very Dilute Colored Solution of n-octyl Methylene Blue Approx. 001$)
Mesh

Procedure

Hesuits

Sample

Grams

Experiment A-7

Washed Ottawa Sand

100

-170

+200

Agitated with
reagent.

No appreciable
color change.

Experiment 3-3

Washed Willemite Ore

10

-170

+200

Agitated with
reagent•

Very appreciable
color removed.

Experiment 33-9

Washed Willemite Ore
Ottawa Sand

1
99

-170

+200

Agitated with
reagent.

Appreciable
color removal.

Experiment D-2

Washed Willemite Ore
Ottawa Sand

10
90

-170

+200

Agitated with
reagent•

Very appreciable
color removal.

Experiment D-7

Washed Calamine Ore
Ottawa Sand

5
95

-170

+200

Agitated with
reagent.

Appreciable
color removal.

Experiment A-3

Washed Calamine Ore

10

-170

+200

Agitated with
reagent•

Appreciable
color removal.
h

EABLE II
notation of Willemite by n-octyl Methylene Blue
Feed; 100 gm deslimed Willemite-Sand
Feed Size: -170 +200
Water: Distilled pH7
Frother: Pine Oil
2nd Cut

Collector
#/T on

Head
i Zn

Frother
#/Ton

Grams

i

Zn

Grams

£ Zn

2-1

0.03

1.0

0.10

9*752

1.92

10.263

1.5

2-2

0.05

1.0

0.10

11.173

2.3

10.502

1.8

2-3

0.06

1.0

0.10

10.765

2.5

11.21

1.9

2-4

0,08

1.0

0.10

9.751

3.91

10.530

3.4a

2-5

0.10

1.0

0.10

10.317

4.21

10.720

3.58

2-6

0.20

1.0

0.10

9.271

3.78

10.207

3.16

2-7

0.40

1.0

0.10

9.987

3.68

10.042

3.27

Seat

1st Cut

to

TABLE II A
Flotation of Willemite lay n-octyl Methylene Blue
Calculation from Table II
Test

1st Out
$ Recovery

2nd Cut
Jo Recovery

Total
# Recovery

Avr. $
Zn

Imp.
Factor

2-1

18

15.4

33.8

1.71

57.8

2-2

25.7

18.9

44.6

2.05

91.4

2-3

26.9

21.2

48.1

2.2

105.8

2-4

38.1

36.0

74.1

3.67

271.9

2-5

43 > 3

38.38

81.81

3.90

318.6

2-6

35.04

32.25

67.29

3.47

233.4

2-7

36.75

32.84

69.59

3.48

242.1

EABIiE III
flotation of Willemite by n-octyl methylene "blue vs size distribution
Feed: 100 gm. deslimed Willemite-Sand
Water: Distilled pH7
brother : Pine Oil approx. 0.10 #/2?on

Mesh of
Peed

Grams
Proth

Zn

4.
.p .

3-1

0.09

1.0

100 - 170

12.329

2.9

35.8

3-2

0.09

1.0

170 - 200

11.940

3.8

45.4

3-3

0.09

1.0

200 - 270

12.453

4.25

52.9

3-4

0.09

1.0

270 - 325

11.879

4.01

- 325

12.107

3.75

45.4

i

•
ON

Head
$ Zn

■S

Recovery

Collector
#/Ton

Seat

Vj O

TABLE IT
Flotation of Willemite "by n-octyl methylene "blue vs. pH. collector 0.09 f/^o n
Feed Size: -200 +270
Feed: 100 gm. deslimed Willemite-Sand
Water: Distilled
Frother: Pine Oil Approx. 0*10 #/Ton

Test

pH

i

Head
i Zn

Grams
Froth

Zn

i
Recovery

Impt.
Factor

4-1

4.5

1.0

8.726

4.9

42.8

209.7

4-2

5.0

1.0

11.785

5.2

61.3

318.8

4-3

5.5

1.0

11.048

6.1

67.4

411.1

4-4

6.0

1.0

10.522

5.8

53.7

311.5

4-5

6.5

1.0

10.707

5.1

54.6

278.5

4-6

7.0

1.0

9.698

4.53

43.9

198.8

4-7

7.7

1.0

9.707

4.2

40.8

171.7

4-8

8.2

1.0

10.644

4.18

44.5

186.0

(TABLE V
Heflotation of Willemite Concentrates with
and without new collector or sand addition
Feed: Various Amounts
Water: Distilled
Peed Size: -200 *270 mesh
Prother: Pine Oil Approx. 0.10 #/Ton

Test

Collector
#/Ton

pH

Head
J 2n

Total
Peed

Hew
Sand

G-rams
Proth

Zn

Enrichment

^
Hec.

6.51

3.26

33.0

5-1

0

7

2.0

100

0

10.256

5-2

0

7

2.0

100

50

9.7^2

5.8

2.9

28.3

5-1A

0.12

7

2.0

100

0

11.65A

9*86

^.93

57.5

5-2A

0.12

7

2.0

100

50

10.A31

8.75

^•37

A5.6

5-1B

0.12

5.5

2.0

100

0

10.975

12.6

6.3

69.0

5-2B

0.12

5.5

2.0

100

50

11.0A7

10.97

5 .**8

60.1

TABLE VI
Flotation of Calamine "by n-octyl Methylene Blue
Feed: 100 gm deslimed Calamine-Sand
Feed Size: -200 +270
Water: Distilled pH7
Frother: Pine Oil approx. 0.15 f Fer Ton
„..r

Collector
#/Ton

Head
Zn

Grams
Froth

Zn

6-1

0.05

6.0

12.753

9.12

6-2

0.1

6.0

13.147

6-3

0.15

6.0

6-4

0.2

6-5

Becovery

Degree of
Improvement

Imp.
Factor

19.4

1.52

29.5

15.5

34.0

2.58

87.7

12.010

23.15

46.3

3.88

179.6

6.0

12.820

25.8

56.4

4.30

242.5

0.25

6.0

15.382

25.0

64.1

4.16

266.7

6-6

0.3

6.0

12.745

29.0

61.8

4.83

298.5

6-7

0.35

6.0

13.109

29.2

63.8

4.86

310.0

6-8

0.40

6.0

13.102

29.8

65.1

4.96

323.0

Test

p

-o

(TABLE VII
Flotation of Calamine 17 n-octyl Methylene
Blue vs size distribution
Feed: 100 gm deslimed Calamine-Sand
Water: Distilled pH7
Frother: Pine Oil approx. 0.15 # per ton
---rr-

1

•+

Zn

Degree of
Improvement

8.18

1.36

18.1

17.9

2.98

39.3

14.923

26.4

4.40

65.66

-270 *325

14.279

24.2.

4.03

57.59

-325

13.840

18.9

3.15

43.60

Mesh of
Feed

Grains
Froth

Collector
tilTon

Head
fi Zn
c

7-1

0.25

6.0

-70

*100

13.295

7-2

0.25

6.0

-100 *200

13.183

7-3

0.25

6.0

-200 +270

7-4

0.25

6.0

7-5

0.25

6.0

Test

P

p

Recovery

03

TABLE VIII
Hotation of Calamine hy n-octyl Methylene Blue vs
pH,
Collector 0.25 #/^on
Feed Sizei -200 f2?0
Water: Distilled
Test

pH

Feed:

100

Frother:

gm deslimed Calamine-Sand
Pine oil approx. 0.15 f/^on

...... 'cpf-----

Head
J> Zn
L

Grams
Froth

.... "d.. —
Zn

Recovery

fi

Enrich­
ment

Imp.
Factor

8-1

4.0

6.0

12.514

26.22

54.7

4.37

239

8-2

5.0

6.0

10.421

35.52

61.7

5.92

365

8-3

5.5

6.0

12.276

32.16

65.8

5.36

352

8-4

6.0

6.0

10.738

35.2

63.0

5.87

370

8-5

7.0

6.0

14.207

28.38

67.2

4.73

318

8-6

8.0

6.0

10.933

29.76

54.2

4.96

269

8-7

8.5

6.0

13.133

24.78

54.2

4.13

224
VjJ
vo

TABLE IX
Heflotation of Calamine concentrate with and without
new collector or sand addition.
Peed: Various Amounts
Jeed Size: -200 ♦270
Test

A

Collector
#/Ton

pH

Head
i Zn

Total Peed

Water: Distilled
Prother: Pine Oil Approx. 0.10 #/Ton
Hew
Sand

Grams
Proth

£
Zn

Degree of
Improvement

c7

Recovery

9-1

0

7.0

18.0

100

0

23.498

34.75

1.93

45.4

9-2

0

7.0

18.0

100

50

25.012

29.0

1.61

40.3

9-1A

0

6.0

18.0

100

0

22.754

38.47

2.14

48.6

9-2A

0

6.0

18.0

100

50

23.741

33.15

1.84

43.7

9-13

0.3

6.0

18.0

100

0

28.075

41.0

2.28

63.9

9-1C

0.3

6.0

18.0

100

50

27.108

37.61

2.09

56.6

Flotation of Los Lamentos Ore hy n-octyl Methylene Blue
Feed: 100 gm deslimed Los Lamentos ore-sand (l/j Total Zn)
Feed Size: -270 -325
Water: Distilled
Pine
Oil
Frother:
Collector
ItJTon
0.05

Frother
#/Ton
0.10

pH

Zn

Hecorery

7

1.69

37.2

63

Imp. Factor

10-1

Head
Zn
1.0

10-2

1.0

0.15

0.10

7

3.80

68.3

260

10-3

1.0

0.25

0.10

7

^.15

70.2

291

10-4-

1.0

0.35

0.10

7

3.65

61.7

225

10-5

1.0

0.25

0.10

^

2.03

53.2

108

10-6

1.0

0.25

0.10

6

4.27

77.1

329

10-7

1.0

0.25

0.10

8

3.16

59.5

188

Test

Enrichment
10-8*

2.5

0

0.05

7

8.24

56.58

3.3

10-9*

2.5

0.25

0.05

7

7.34

49.21

2.94

10-10*

2.5

0.25

0.05

6

7.95

55.45

3.18

* Heflotation of feed once concentrated

TABLE XI
Flotation of Los Lament os ore by n-octyl methylene blue
Feed: 100 gm. deslimed Los Lamentos ore (6/6 Total Zn)
Feed Size: -270 +325
Frother: Pine Oil
Water: Distilled
Head
1o Zn

Collector
#/Ton

Frother
#/Ton

pH

11-1

6.0

0.05

0.15

7

11-2

6.0

.15

0.15

11-3

6.0

.25

11-4

6.0

11-5

Zn
f

Degree of
Enrichment

Recovery
i

Imp.
Factor

7.3

1.21

21.2

25.6

7

84

1.40

26.3

36.8

0.15

7

13.7

2.28

41,5

94.6

.35

0.15

7

25 4 9

4.25

73.1

310.7

6.0

.35

0.15

4

23.74

3.92

64.1

251.3

11-6

6.0

.35

0.15

6

34.8

5.8

74.0

429.2

H -7

6.0

.35

0.15

8

21.7

3.61

4?*6

179.0

Test

.

.......

f l \ /??. %

T in

//V T c T f i L
r\>

CCrtCErtr/e& TE

(*
is

i?

5

*
3

*
\
5

<*>

*
N
ft

(A
o
ft

i
0
'I

x

f*!
u

i

*
b

ft

Si

S
\

*
(ft

'a

h

(ft
(ft
IN
N

*

h
ri

i
H

1

h

i
*\
s
*

^

\3

*

i

ft

h

x
N

,

1

T
\
h
h

<5

n

n

t)

s
0

hh
tv*i

*
v

r%

(ft

(ft
h

ft

*

b
01

* £
N.
ft
h

T or& L .
VS.

p e e c c a i t

EOUA/O&

"
O E

y y

/

l l

E n /T E r"

z.n

C O L L E C T O R

ror&L % Zn 7?ECOV£7?Y

too

80

60

20

/O

0-1

B

o u n d s

n -o

c t y l

m e t h y l e n e

g l u e

£=>£T? TON t%, Z n VY/LLEM/TE EEED
f

/ <$ O T? E

-q-

45

//V r ^ f ^ O V £ L f * 7 £ /\ ir F 'ftC T O T ? OF" 1 %

Z n

W!LLtzr?/T£ F'FTEO r-J/O+Zcc /^£SH)
VS.

T^g

u

N o> s

of

' co£L.£C Tore

lop

0.1

T^OUA/O S

n- O C T y L

7 > £ -/e 7 ~ o /*

/

%

2irn

A 7F T H Y L £ A/£
w /

7 r/ q t / / e £

l l e

*r

m r e

&GU E
f e e e

*

k6

T^E.7? C£lA/r z:/? /A/ C O a/CEA/T/?ETE
VS,

7>ftr?rfC L£

e / z e

W / LLE M /T E

j %

o r

EE E D

4
UJ

k
k

3

kj

o

a

CJ

*

v

c:

N

/

-2?o*3LS

A 7E S M

EEE E

-0 .0 9

r E

E E E E

E ’& U E O S

/ %

Z „

V J l L L E M t 1~E

COELECTor?

/ ^ / G u r z E

e

Z=>E& E o a

*7

T ^ E /^ C E N r

W/LLEMiTE

CONCEPTf? f)T E

1/3. p H

Z n

IN

O f CELL. C O N T E N T S

7

6
Id
k
<c:
ft:
k
<:
kj

"-r*— a

4

*
<o

3

\

Q

2

N
nP

0s

2

6

pH
//
\a/

or

CELL

1L L E M )T E

"

3

7

CONTENT<S

TEEC

~

r / Q U P E

9
oE

/ %

Zn

O. O 9 rot/N&fS CO L L E C T O R

7

m

/C7 F / P O V £ n £ N J '

r&CTOR

1/.5. p H

CCC D

of

J %> Z n

OF CELL

WlLLErtlTE

C O A /TF N T S

HOJ
CfrJ
- /V 3W 7A
O d fd U /

to o
so
L..

4-

p H

s

OF

&

CELL

7

a.

COA/TLHTL

O F

" W / L L C M f T C v" C C E 0 - 0 . 0 9

r t Q U F C

ct

/ %

JO

2

r>

F o t / H O s C&tL

&

l

£ C T or?

P E R C E N T " C G L E M i N E * ZTn I N
p'OUNOE

OE

COLL EC TC f?

% Z.n

//V

C ortC E N T R R T E L

VS.

CONCENT&ftTE

10

C.J

FOUNDS
REE

n-OCTVL

TOM

rtETH YLEN E

C n L & M /N E

F I G U R E

9

BLUE

G°/& Z n F E E D

//
R C , \

; /

CHLRM/NE 'Z

/

\/~ • n o

50

o w e :

C o l l £ C t o /?

JOO

&o

o

A

40

N

1C

O.J

/

ON l :

TON

n-££TX
Z
. A
7
ZTH

/L £ / / £

G °/o £ n COL 0/0 /U L
Vv,;y/rZ

O: c

NT A

n

51

/N PRO vTr/EN r

o r

r f t C T C F ?

6 %

7L n

C N L T M ///C rO £ l> r too + t yy /y£ 5 H )
l/vf-. N o r r r y

o r

C

ool. e c

r o r

zoo

o.z

0.1

m j r r o

t e r

to n

n - r c r y L

6 %

n e t a

21*

o.

0.3

/ v l .e n e

C ftLN M tNE

r~/arrr //

ic l o

c

F E EO

F>£. A - C £ A / r

\/5.

z:

n

iN

C OsSC£.

/=V9/t*r/CL.£r ^/z£Z o r
r ? I N ET

52
A/ r / P

/9 7- £:

£ % z:/?

r £ E O

k
<e
I

*
u

*
0

£
\

N
ox

- /rf -<
■a c o

/VzTs/y

o r

r ' r e u - o . z r

- 2 0 0 <■■2 / 0

r £ £ .£ >
P o r A /r r s

P / CU/PE

*=>% r

n

Cp>t-&m/ n e .

C O L . l. E C r o / ^

IS-

r £ s ?

TOM

53

/ ^ r / P C C N T " C f i L r t r U N E * Z. n ( N

VS. p h or cell

C OM C E N T /rft T fZ

Con r onto

7

yo H

O F

F F E O

C. £■ L L

C.0/7 / E f tT S

- O.ZS F C O N F O

o F

€> °A? 7Cr> £Fi./-?M(tJC

COLLECTOR

F / C U F E i /3

F'FF

TON

5^

0
c r r r r z / A / r

/,/r
r

m

r H C T o r?

1/ 3 . p &

o

o r

o £

c

n

O 9b £ n
.l

c

o n

t e

n

t s

zoo

70 C

So

a

9

.pH or cr l l cop/tents or r°/o £ n crrrr/A/i
r ' r r o

-

o

.e

s

r o t /m

o

o

n o u r r

C

o l

1 «

l

e

c

t

o

/•<

r

r

r

r o r

/rip.

X

c

Jvi

>
fv,

t

o

r

u

VEmE

h
N

s-

\

kj

X

N T

‘v

■>

Fn

>3
X
4.,:
C;

a

/ r?PRO

^3

f

c 7-<r /a

X.

r*.
V
X
X

•>

vs . C oe l E C, r o n?

u

LOS> L & M C N T O S

e %

56
~2Ln O P E

l-EC.tc &

x
O'
N
o
o

V
)

N

PC U A' O «. n - OC.T Y L

% z: n //V CotfC£/JTh'FiT£

vs. Col l.E CLTofr
r

O
*
o
O

c

IB
72

N
6

_

1~ .

<?2
P04SSS£2S>

n- O C T V 2-

/V

F J Q U P E

£TT H Y' L. £ A/ £

1 6

& L iJ£

f

57
DISCUSSIOH

Examination of the data demonstrates that in every case
n-octyl methylene "blue functions as a collector for zinc
silicate.

The experimental data further affords confirma­

tion of the theory that a modified mordant dye will function
as a selective collector for the material which it mordants*
The zinc silicate ores tested were (l)
(2 )

Calamine or Hemimorphite, and (3)

Willemite

Los Lamentos ore,

Each showed "both enrichment, and improvement when subject to
flotation with the modified dye.
In view of the results obtained with these various zinc
materials it will aid the discussion to briefly review these
silicates,

(l)

Willemite (1 2, 5 1 * 5 9 ) zn2SiO^ occurs in

masses or in crystal; Moh hardness 5*5; sp. gr. ^.1; color,
pale yellow when pure; lustre-resinous; translucent on thin
edges.

Crystal structure; hexagonal prisms, with a 3—sided

(rhombohedral) pyramid on the ends.

Color when pure is whitish

or greenish yellow, but with small amounts of impurities, it
may be flesh—red, grayish white or yellowish brown.

The Wille—

mite used in this investigation was fairly pure and was green­
ish yellow.

It was obtained from Words Natural Science

Establishment, Inc., Rochester, New York.

It was subjected

to heat and failed to give off water vapor thus indicating

lack of any calamine which it often resembles when massive.
(2)

Calamine.

(13» 1^» 52) Z^CQKjgSiO^ occurs as cry­

stalline linings in cavities, or as stalactitic masses; Mah
hardness 5 . specific gravity 3*^1 color white, sometimes
bluish or greenish shade, also yellow to brown.
to translucent.

Transparent

Compositions recorded as (ZnOH^SiO-^,

H^ZnSiOjj or HgO^ZnO-SiO^.
unchanged at 3^0 C.

Water is given off at a red heat

The Calamine used in this investigation

was hemimorphite (calamine) of the orthorhombic type.

It was

obtained from Ward’s Natural Science Establishment, Inc.
Hemimorphite structural (Z n ^ Q H ^ S i g O y *^0) according to
Phillips (60) is orthorhombic pyramidal.

The crystals are

peculiar in that the two ends are terminated differently.
The percentage zinc indicated the presence of impurities.
(3)

Los Lamentos Ore:

This zinc silicate ore was ob­

tained from the Eagle-Pitcher Company for testing on a commer­
cial ore.
The name of the property from which the ore sample came
was Los Lamentos.

This mine is located 30 km. West of the

town of Villa, Ahumada on the Mexican National Railroad in
the state of Chihuahua.

It was an old lead producer and a

limited amount of zinc silicate ore remains in the old stopes.

( 11 ).
This ores' analysis is as follows:

59

51.3/^ Zn
1.5$ Pb
2 .2/» 3Pe
•068$ Cd
23.0# Insol
Unfortunately, it was not possible to obtain a sample
containing less zinc from this source.

Tests were therefore

conducted in a similar manner as employed on the Willemite
and Calamine.

The Los Lamentos mine ore was dry ground,

deslimed, and classified into various mesh divisions.
Tests were run on this ore in the general range of con­
centrations used in the fundamental research.

Ottawa Sand

of the same size distribution was used to dilute the feed to
the proper total percentage of Zinc*
THE C0LLSCT0B
The procedure for preparation of 3 n-octyl 2,8 tetra
methyl diaminothiazonium chloride, namely, n-octyl methylene
blue, is given in the appendix.

Examination of this procedure

will indicate the uneconomical feasibility of preparing large
quantities of collector for commercial use.
The difficulty of this synthesis was brought about by
the inability of finding a reaction or reactions of methylene
blue with a compound or series of compounds, which would pro­
duce n—octyl methylene blue.

A search of the literature

60

failed to reveal any* method for introducing the n-octyl
group into the "benzene ring of 2,8 tetramethyl diaminothiazonium chloride (methylene "blue).

All authorities consulted

agreed that a direct introduction of a hydrocarbon radical
into the benzene nuclei of methylene blue was not feasible
and that the structure of dye would probably be altered.
In any case, the subsequent separation and purification of
a product would be a tedious procedure.
Various reactions were tried in an effort to produce
the desired collector by short-cut methods.

All failed and/or

gave indications of lack of coupling, impossible purifications,
rearrangement and apparent distruction of n-octyl chain,
which was known to be necessary for flotation.
the reactions used were evolved.

Finally,

See Tables A and B,

This

method involved the preparation of compounds containing the
n-octyl group which could be reacted in final coupling re­
action to produce n—octyl methylene blue, and thus assure
the minimum danger of side reactions and ease of purification.
Thus, it is reasonably assured that if the coupling of
ortho-octyl dimethyl aniline with the thiosulphonic acid of
p-amino dimethyl aniline gave a product which possessed the
properties of metiylene blue, the compound would necessarily
have to be alkyl substituted methylene blue.

(Reaction *0.

The entire procedure was long and tedious because many of the

61
reactions gave poor yield.

For example, reaction G or Table B,

is chiefly meta and para directing only a small yield of the
required ortho-compound was obtained.

Inspection of structure

coupling product clearly shows that no reaction to produce the
dye should take place with other than the ortho n-octyl com­
pound since the other hydrogens are involved in the coupling
reaction.
The final purified material had many of the properties of
methylene blue.

Description of product is:

with bluish-red metallic lustre.

A pastey material

It was slightly soluble in

water, insoluble in ether and benzene, soluble in alcohol.
Heated on platinum foil, it gave greenish-violet vapour.
burned with smokey flame, but left no ashes.
indicated the compound was zinc free.

It

The lack of ash

It dissolved in concen­

trated sulfuric acid and was unaffected by dilute sulfuric
acid.

It was not appreciably affected by ammonia.

chloride gave a precipitate.

Stannous

The above properties indicate

that the n-octyl methylene blue possesses many of the proper­
ties attributed to methylene blue (8).
finally, a small sample was dissolved in water-alcohol,
heated to boiling while carbon dioxide was passed into the
flask.

Titanium trichloride was added to the solution until

it was decolorized.

It required approximately two equivalents

of iron (in terms of titanium trichloride) for reduction of

62
one mole of the n-octyl substitute compound (mol. wgt. 331*6 ).
This definitely indicates that this compound was n-octyl
methylene blue*
This method is based on the assumption that two equiva­
lents of hydrogen are required for conversion of n-octyl
methylene blue into the leuco compound according to the equa­
tion:
Cq H ^ H

iq^

S cI ^

C8H17Gl6H 20N3Scl

Much work has been done on the volumetric determination
of methylene blue and other dyes by this reduction method
(35. 39* 47, 48, 68, 69).

This method of analysis is very

popular in United States dye plants and is considered satis­
factory.

It is assumed that the conditions of final reaction

were sxch that the n-octyl group remained unchanged and that
it did not rearrange.

Based on these facts the collector is

called n-octyl methylene blue and would chemically probably
be 3 n-octyl 2,8 tetra methyl diaminothiazonium chloride.
SELECTIVE MOamUT ACTION
Inspection of Table I will show the results which demon­
strate the selective mordant action of n-octyl methylene blue.
The washed Ottawa sand removed very little color for colored
solution (Test A-7 ).

However, the zinc silicates, Willemite

and Calamine, when agitated with the dilute colored solution
showed appreciable color removal.

(Test B—3 , and A—3).

63
Inspection of the settled material evidenced the fact
that mordanting had taken place, the material was dyed.

Re­

peating this procedure with various amounts of calamine,
Vfillemite and sand, produced the same results (Test B-9 , D-2 ,
D-7).

This demonstrated to the writer that the collector has

some degree selective of mordanting for the zinc ore over the
silica gangue.

This is substantiated by all the data, how­

ever, lack of greater selectivity in later tests indicates
some reaction at the concentrations necessary to bring about
flotation,
FLOTATION OF WILLBMIEE-ZINC SILICATS
The results of the flotation test for Willemite by
n-octyl methylene blue will bo found in Tables II, IIA,
III, IV, V, and Figures 3»

5* 6, 7» &ad 8.

For all the

work reported on Vfillemite flotation, a one percent concen­
tration was used,

Fnough concentrate had to be taken to

allow sufficient recovery as well as to give adequate sample
for analysis.

In all cases, duplicate samples were analyzed

(b- grams per sample).
run.

Occasionally triplicate samples were

As pointed out in the procedure, the analysis of zinc

silicate is not an easy matter.
It is possible that the amount of material collected
might lead one to suppose that possibly some mechanical carry­
over gives a concentrate lower in zinc than the feed.

This

64
is due to the fact that the specific gravity of silica is
under 2*5 • Any mechanical carryover would tend to lower the
percentage of zinc in the concentrate, recovery, etc., rather
than raise them.
AMOUNT OS' COLLECTOR:

Inspection of Tables II, IIA give

the conditions used in the study of the effect of increased
amounts of collector upon the flotation of Willemite.
cuts were taken for each test run.

Two

An attempt was made to

take about the same amount in each cut.

It is indicated that

in all cases, tile second cut is lower in percent zinc in con­
centrate as well as percent recovery of the total zinc in
the feed.

However, the drop off of concentration in the

second cut is not as sharp as one might expect.
Around 0.1 pound collector per ton gave the best concen­
tration in the two cuts.

Inspection of figure 3 indicates a

sharp increase in concentration to around 4.0p, thence drop
off to 3 .5$ and after that, no appreciable change even with
collector amounts of 0.4 pound per ton.

An increase of collec­

tor on Vp Willemite feed has only a slight depressant effect
on the flotation once the maximum is reached.
The percent zinc recovery vs. amount of collector curve
reaches a maximum around 0.1 pound collector per ton and is
depressed slightly with increased amounts of collector.
then levels off even at 0.4 pounds per ton.

It

At low collector

65
amounts, very little recovery is obtained.

First cuts in

all cases show higher recovery than second cuts "but, as in
the case of percent zinc in concentrate, there is not an ex­
tremely sharp drop,
She improvement factor (55» 63) shown in figure 5 reaches
a maximum of 313,6,

She improvement factor is one of the

better methods of demonstrating the effectiveness of flota­
tion,

It is obtained in this case by taking the percent

zinc in the concentrate times the percent recovery.

It ac­

tually should be enrichment times the percent recovery,
•Enrichment is obtained by taking percent zinc in the concen­
trate and dividing it by percent zinc in the head or feed.
It is apparent with 1>& feed that percent zinc in concentrate
is equal to the enrichment.

Often this enrichment is reported

as degree of enrichment or as percent enrichment, that is, one
hundred times the enrichment.
She percent recovery of zinc is obtained by taking the
grams of zinc in concentrate divided by grams of zinc in the
head times one hundred.

She above methods of calculating are

used in the data presented.

She improvement factor therefore

combines the separating efficiency and the selectivity into
one factor.

One eliminates "good" results as are often report­

ed in flotation literature and research,

Shas, one can have

high recovery but very low enrichment or very hi^ti enrichment

66
and very low recovery.

The improvement factor presents the

final or overall picture.
Since sine silicate has never "been successfully floated
in the laboratory or in particularly the commercial field,
there exists no criterion for what a satisfactory improvement
factor would he.

It appears that any improvement factor over

two hundred is definitely a step in the right direction.
She improvement factor curve, Figure 5» shows a sharper
rise with increased amounts of collector than either the per­
cent zinc in concentrate or the percent zinc recovery curve.
The depressant action is also much sharper, dropping improve­
ment factor from 318 to 233 and actually indicating a slight
recovery with higher amounts of collector (0 .^ pounds per ton).
It thus appears that the amount of n-octyl methylene
blue used as a collector for Ifp zinc Willemite silicate ore
must be critically adjusted for maximum flotation, under con­
ditions used in Table II.

It further appears that increased

collector depresses slightly the flotation but then holds at
a fairly constant improvement factor.

We may theorize in

this case that a certain amount of collector is necessary
to form the “envelopes" or sufficient mordant and that in­
creased collector tends to block the flotation of the “en­
velopes" , but only to a fixed amount.
FEED P-oRTICLS SIZE:

Table III gives the conditions

67
used to study the effect of feed size on flotation.

In this

study, only one cut was taken, collector was held constant at
0.09 pounds per ton.

As in all tests reported in this inves­

tigation, the feed was subjected to a conditioning period
with all the collector added before collection was made.
This had proven, in preliminary tests, to give better results
than a step-wise addition of collector.

The results indicate

that the minus 200 plus 270 feed gives the highest percent
zinc in concentrate as well as the high percent recovery.
Examination of curve of percent zinc in concentrate vs. parti­
cle size of feed, Figure 6 , would lead one to deduce that one
must approach a minus 200 mesh particle size to get maximum
freedom of zinc containing particles and that subsequent
particle size reduction drops the zinc in the concentrate
not too greatly.

The lack of an appreciable drop is believed

to be due to two effects, namely, (l)
the willemite and (2 )
feed.

low concentration of

the purity of ores used in making the

Excessive sliming was not encountered with increased

fines as in other cases.

However, the drop that does occur

appears to be due to sliming.
pH OF CELL C0HTEHTS: Using the optimum conditions of
the minus 200 plus 270 particle size, and the collector con­
centration of approximately 0.1 pounds collector per ton, the
effect of pH changes were studied.

A n alkali solution could

"be controlled by dilute caustic, an acid solution used in
conjunction with dilute hydrochloric or sulfuric acid.
spection of Table IV reveals an interesting fact:

In­

as the

solution becomes more acid, the percent zinc in concentrate
reaches a pronounced maximum at a pH of 5*5* falling sharply
on either side of this pH,

We should note that the 4.9 per­

cent zinc in the concentrate is only on 8.726 grams of froth
and would be lower on a larger cut sample.

As the pH was

increased the percent zinc in concentrate decreased more or
less sharply but the drop appears to level off at a pH of
around 8.5*
The plot of percent "willemite11 zinc in concentrate vs.
pH of cell contents, Jigure 7* evidences this drop on either
side

of the 5*5 pS.

It appears that as the pH increases,

its effects tend to approach a constant value.
The percent of recovery of zinc in feed has a maximum of
67.4/* at the pH 5*2 again dropping on either side.
Bharp drop is noted between the 5

"the 4*5 pH.

A very
This can

be partially explained by the smaller amount of cut.
should show a less sharp decrease.

This

The increase in recovery

between 7*7 a-nd 8.2 is most unusual in light of the fact that
inspection of I'igure 8 shows that where the discrepancy be­
tween the pH* s of 4,5 and 5 are corrected in the improvement
factor, the discrepancy between 7*7

8,2 are not.

That is

to say, the improvement factor went from 318,8 at a pH 5 to
209.7 at a pH 4.5, whereas it increased from 171.7 to 186.0
in the latter case.

However, the curve of the data taken

indicates a gradual drop in improvement factor with increased
pH.
It may he reasoned for Table IT that at a pH of 5«5*
the maximum collecting action is due to the better “enveloping"
of the zinc particles, and/or the depressing of the gangue
due to the acid and/or the activation of the zinc particles
due to the acid.

There was some indication that the use of

hydrochloric acid for pH adjustment increased the improvement
factor.

It may be deduced that under conditions of Table IV

the improvement factor is very sharply affected by the pH.
This was not so marked in the study of the effect of pH on
the flotation of the calamine and Los Lament os ores.

pH may

affect more strongly the unhydrated zinc silicate, particular­
ly in terms of the improvement factor.
HHi’LOTA.TION:

Inspection of Table V reveals several in­

teresting factors which appear to effect the reflotation of
once floated ore.
show that (a)

Inspection of Test 5—1» 5“3A» and 5*“1^»

reflotation gave an enrichment of 3.26 and a

recovery of 33*0 percent, Cb)

the addition of more collector

increased the enrichment to ^•93 » and (c)

increasing collector

and adjusting the pH gave an enrichment of 6.3.

Thus, one

70
concludes that reflotation, not only is "beneficial, "but addi­
tional reagent and pH adjustment gives additional improvement.
The series of Test 5—2, 5-2A and 5-23, gives much food for
thought•

This series used the s ame percent zinc in the feed

hut was made up hy taking 50 grams of new sand, with 50 grams
of concentrates to give a final 100 grams of 2 percent zinc*
When subjected to the same set of conditions of reflotation
as the other set, it gave the same general results hut in each
case much less degree of enrichment*

It thus appears that we

have some type of equilibrium between the envelopes particles
of gangue and zinc, and solution.

This condition seems to be

shifted by the introduction of new gangue material.
FLOTATION OF CALAMINE ZINC SILICATE
The results of the flotation test for calamine by n-octyl
methylene blue will be found in Tables VI, VII, VIII, and IX
and Figures 9* 10, 11, 12 and 13.
In all the work reported here a 6 percent zinc concentra­
tion was used.

A test on mechanical carryover established a-

gain that carryover produces a concentrate lower in zinc than
the head*
AMOUNT OF COLLECTOR:

In this study slightly more cut was

taken but only one cut was made.

There is a gradual increase

in percent zinc In concentrate with increased amounts of
collector.

0*2 pound per ton seems to be the levelling off

71
point.

One notes a slight drop at 0.25 pounds collector per

ton, which is attributed in part to the excess cut over the
0.2 and 0.3 pounds collector per ton.

Figure 9 which shows

the plot of collector vs, zinc in concentrate demonstrates
that apparently there is no depressing effect hy additional
collector, but rather a levelling off above 0.3 pound collec­
tor per ton.

Comparison with Figure 3 indicates that we do

not have a maximum and also that it requires considerable more
collector before one reaches the decreasing rate of increas­
ing zinc in concentrate with collector change.
Che percent recovery of zinc has a gradual increase
with increased amounts of collector.

Che percent recovery

of zinc tends to level off at slightly over 60 percent and
has only a slight increase with increased collector after
that.

Che high recovery at 0.25 pound collector is due again

to the high cut of concentrate.

Comparison of Figure 10

with Figure 4 shows that increased amounts of collector does
not produce a sharp maximum and further, apparently does not
have any depressant action on the percent recovery of zinc.
Chis contrast is even more marked when we examine the
effect of collector on the improvement factor.

A maximum

improvement is reached of 323 at the high amount of collector
addition.

Examination of data in Cable VI clearly shows an

increase over 0.25 to 0.3 pounds per ton does not greatly

72
alter the improvement factor, percent zinc in concentrate, or
the percent recovery of zinc.

Instead of the sharp drop in

the improvement factor with increased collector as for Willemite (Figure 5) we have only a steady increase.
One might attribute this to the nature of the calamine
zinc silicate and/or the higher concentration of zinc silicate
which has a more steady demand.

However, the improvement

factor comparison leads one to conclude that the modified dye
mordants or ,,envelopes,, these particles effectively in both
cases.

This had been indicated in the work reported in Table I .

FEED PARTICLE SIZE:

Table VII and Figure 12 gives the

results of effects of particle size on percent zinc in concen­
trate, degree of improvement and percent recovery of zinc
for the calamine feed.

It should be noted that the work re­

ported in Table VI was made on minus 200 plus 270 feed.

This

mesh feed had been used because the work on Willemite indicated
this particle size was necessary to free the zinc silicate.
This fact is confirmed by the data of Table VII.

A slightly

coarser feed was used in test 7—1 namely, minus 70 plus 100.
In this range, the degree of improvement was only 1.36 with a
zinc recovery of 18.1 percent.

Apparently the zinc particles

were not free enough for flotation.
ed with the minus 325 feed.

Low results were obtain­

Considerable trouble was en­

countered with this feed in sliming.

It appears that the

A

73
calamine load considerable impurities in it which gave trouble
when released by grinding*
A higher percent of impurities was found in calamine than
in the Willemite when the pure ore was analyzed.

Of course,

this condition of sliming is not improved by the increased con­
centration used in the studies on calamine.
pH OF CELL COHTEHTS : The conditions used for this study
and results are given in Table VIII and Figures 13 and 1A.
The optimums established by the preceding work were employed.
The same method of pH adjustment was used, except the pH was
adjusted in steps of one-half a pH.

The effect of pH on per­

cent zinc In concentrate increases to a flat maximum between
5 and 6 .

The percent zinc in concentrate has its greatest

drop as the pH is increased.

It appears from inspection of

Figure 13 that the percent zinc in the concentrate is more
gradually decreased on the alkaline side than on the acid side.
Comparison with the willemite curve, Figure 7, will show that
the maximum for calamine is relatively lower and flatter than
that of the willemite.
by small changes of pH.

Calamine seems less sharply affected
Here again the acid apparently acts

as an activator for zinc silicate particles, allowing more
selective mordanting or "enveloping" of zinc particles over
the gangue•
Inspection of Table VIII shows that enrichment follows

74
the same general trend of the percent zinc in concentrate.
The percent recovery of zinc shows the same flat maximum be­
tween the pH of 5 a-nd 7»

However, it is noted that the drop

above the pH of 7 is just as pronounced as below the pH of
This behavior is different than that of willemite, the latter
actually had an increase in percent recovery of zinc as the
pH went up.
The improvement factor for calamine reaches a maximum
value of 360-370 in the range of pH 5 to 6.

It not only has

a higher improvement factor than Y/illemite, but the maximum
is much flatter.

This would indicate under the test conditions

of Table VIII, that (a)
acid side, (b)

the best flotation is obtained on the

that maximum enrichment, percent zinc in con­

centrate, percent recovery, and improvement factor, exists
over a wider range of acid pH than for willemite silicates,
(c)

that selective "enveloping" is taking place, and (d)

that above a pH of 8.5, the flotation is greatly decreased.
One might theorize that the effect of the hydrogen ion
(pH) has a marked effect over the "enveloping" of the particles
over a wider pH range on the hydrated zinc silicate particles.
However, there is undoubtedly some other effect since ordin­
arily the hydrated ores have a tendency to be more difficultly
floated.

In fact, one must make the particles water repellent

to achieve flotation.

75
R bUj'JjOTATION OT CAIAMIUE: Table EC shows the results
of the reflotation of calamine with and without pH adjustment,
new gangue or additional collector*

In light of above re­

sults, reflotation was attempted with pH adjustment without
an additional collector.

This is slightly different than

the procedure followed for willemite, see Table V .
Test series 9-1, 9-1A, 9-1B, show that reflotation takes
place with an enrichment of 1*93 a-nd recovery of

S\ir-

ther, that merely adjusting the pH gives improved enrichment
and percent recovery of the zinc*

However, an enrichment,

2*28 on the 18 percent head, is obtained by pH adjustment and
the reconditioning with additional collector.
Test series 9-2, 9-2A, 9-2B , was obtained on a feed of
the same final concentration.

It was obtained by diluting

a more concentrate cut with new gangue (sand).

This series

of tests shows again that new gangue decreases the effect of
reflotation of the once floated material.

VJe obtain only a

1.61 degree of enrichment by reflotation when the new gangue
is added, even with the constant amount of head and percentage
zinc.

Adjustment of the pH before re flotation improves the

percent zinc in concentrate and the percent recovery of zinc.
However, the improvement is not as great as for test 9 —1A*
The addition of more collector improves the percent recovery
and percent zinc in the concentrate but not as much as in

76

Test 9—lC»

Even additional tests run with more collector

added to a 9-1C type sample, failed to give the expected in­
crease in flotation.
One might theorize that the "envelopes'1 are shifted,
"blocked, or altered by introduction of new gangue.

Further,

that due to some equilibrium shift or interexchange between
particles, the tendency to "reenvelope" is diminished.

It is

hard to believe that the gangue would destroy the polar or
non-polar group of the modified dye.
FLOTATION OF LOS LAM2SET0S ZINC SILICATE
The results of the study on this commercial ore is re­
ported in Tables X and XI and Figures 15 and 16.
tigation was made on feeds having, (a)

This inves­

the same percentage

zinc in the feed as in the willemite investigation and
(b)

the same percentage in the feed as in the calamine in­

vestigation.
It was necessary to use a finer size feed to get the
maximum release of the zinc.

However, sliming was encountered,

particularly in the 6^ Zn test.

Repeated desliming before

preparation of feed gave some relief.
ONE PERCENT LOS LAMEHTOS FEED:

Inspection of Table X

shows that the amount of collector necessary to reach a maxi­
mum percent zinc in concentrate is higher than for willemite.
Further, that once the maximum is reached, very little de­
pressant action takes place.

There is nowhere near the drop

77
in flotation as for willemite feed.

The percent recovery of

zinc is favorable with that obtained on willemite.
improvement factor reaches a maximum at 291.
is lower than for willemite.
is probably due to (a)
(b)

This maximum

The increased collector demand

the difference in silicate structure,

impurities in the Los Lamentos Ore, (c)

tions.

The

sliming condi­

Comparison of J’igure 15 with figure 3 and ^ show the

less sharp effect of increased amounts of collector in both
the pre and pos maximum points.
The effect of change of pH showed the best improvement
factor obtained, 329* was at a pH of 6 . A drop in percent zinc
concentrate, percent recovery of zinc and improvement factor
was noted at both the lower and higher pH* s.

The maximum im­

provement factor which is lower than for the willemite might
be explained by the fact that this ore probably contained some
zinc as a hydrated silicate which is not as easily floated as
the dehydrated willemite.

It is further possible that all the

zinc is not in the form of pure silicates and that n-octyl
methylene blue is not as an effective collector on the other
forms.
Test series 10-8, 10-9, and 10-10 were run on once concen­
trated Los Lamentos Ore.

Heflotation produced an enrichment

of 3.3 with a zinc recovery of 56.58.

Additional collector

and reflotation without pH adjustment gave both enrichment and
increased percent zinc recovery.

Increased collector and pH

4

78
adjustment did not give any improvement over the straight
reflotation.

This is in contrast to the results obtained

with willemite and calamine.
analysis, is not so marked.

However, this contrast, on close
The real change is in test 10-8 .

That is to say, we apparently reach a fair recovery without
the need for additional adjustments before reflotation.

The

recovery of 56.58^ of zinc on Los Lamentos ore vs. 33*3/®
recovery on the willemite on straight reflotation indicates
better chance for improvement of this commercial silicate
than for willemite by merely a multiple cell flotation pro­
cess, without additional collector.
SIX PERCENT LOS LAMENTOS NEED:

Inspection of Table XI

and Figure 16 will indicate that flotation of this ore is
affected by the n-octyl methylene blue.

The percent zinc in

concentrate is gradually increased with increased amounts of
collector and is 25.^*9 percent with 0.35 pound collector per
ton.

The rate of change with increased amounts of collector

is much lower for this ore than for the calamine (compare
Figures 9 with 16).

Figure 9 indicates more recovery might

be obtained by additional collector.
The percent zinc in the concentrate vs. amount of collec­
tor shows a much more gradual, increase than with calamine or
willemite (compare Figure 16 with Figures 7 and 9 ).

An en­

richment factor of 4.25 was obtained with 0.35 pounds of

79
collector per ton*

While the improvement factor went to

310*7.
It may be concluded that under the test conditions of
Table X and XI that n-octyl methylene blue functions as a
collector for the Los Lamentos ore*

Fair amounts of this

collector give increases in percent zinc in the concentrate
and percent recovery of zinc*
DEPRESSANTS AND ACTIVATORS
Only a few preliminary tests were conducted on the
effect of various materials as depressants or activators.
worthwhile success was obtained with any material.

No

Any de­

pressants for silica also tended to retard the flotation of
the zinc silicate.

The same was true of activator.

It is

interesting to note in the patent literature (2, 16, ^1, 5^»
61, 62) certain claims regarding the function of additive
materials.

For example, one patent (5^) claims that sodium

sulfide with an aliphatic amines collector containing from 8
to 10 carbons activates flotation of desired material away
from a silicious type gangue, while another patent (16) claims
the silicious gangue particles can be floated away from the
desired material using aliphatic amine having 10 to 18 carbons,
using sodium sulfide as a depressant.
majority of gangue was silica.

In both cases, the

Still another patent claims

amines with 6 to 16 carbon atoms acts as a collector for

I

80
ailica without a depressant or activator.

However, no lit­

erature or patents claims the successful concentration of zinc
silicate "by floating it or the gangue,

use of various

agents should certainly he extensively investigated with the
type collector developed in this work*

A depressant or an

activator appears to offer excellent promise in the pH range
between 5 and 7*
ACCURACY AND SUMMARY
The results of this investigation on the three zinc
silicate ores by the newly synthesized collector called noctyl methylene blue should be taken only as trends.

The

11optimum" conditions given are by no means recommended condi­
tions for commercial flotation of zinc silicate ores.

These

“optimums” served as guide posts in this investigation in
studying the variables, and the behavior of the new collector
in a general way.
The results obtained are certainly a direct function of
the condition of the various tests to project this new theory
of a collector for zinc silicate, and the conditions estab­
lished is not intended*
It is hoped that the results and “optimums" herein re­
ported and discussed will serve as a guide for future inves­
tigation on zinc silicate.

It is hoped these results will

give encouragement to the pursuit of the new theory of zinc

81
silicate flotation, that new modified mordant dyes will he
prepared and investigated along with the effects of carbon
chain lengthy

So that many of the trends can he more fully

studied and explored, that answers to such questions as why
the pH has such a marked effect on flotation and how its
mechanism can he exemplified.
It Is strongly believed, hased on this investigation,
that the solution to successful flotation of zinc silicate lies
in pursuit of this new mordant or "envelope" theory, rather
than in the past approaches presented in the Introduction.

82
CONCLUSIONS
Based on the results and discussion herein adduced
the following conclusions are made.
A.

She synthesized alkyl substituted dye herein de­

signated as n-octyl methylene blue is shown to function as
a collector for the zinc silicate ores, willemite, calamine,
and Los Lamentos ore, under the conditions tested.
B.

This modified dye appears to offer a new approach

to the flotation of zinc silicate.

It is theorized that

selectivity for the zinc silicate is tied in with the mordant
action of the dye, further, that the zinc particles are
"enveloped11•
C.

It is demonstrated that the factors of pH, particle size,

amount of collector, affect the percent zinc in the concentrate,
percent recovery of zinc, enrichment of the product, and the
improvement factor in the flotation of zinc silicate by
n-octyl methylene blue.
D*
C.

That certain trends exist for the factors listed in

Further, that under the conditions of the tests "optimums"

appears to exist for the zinc silicate ores studied.
E.

That the commercial synthesis of n-octyl methylene blue

is not practical.

The approach, using this compound as a

collector is however, well justified by our present knowledge

83
of dye mordants as well as the presently developed theory of
surface chemistry as related to mineral flotation.
F.

Farther investigation on the effects of activators

and depressants, and trends reported herein might he con­
ducted.

APFEMDIX.

85
APPENDIX

Preparation of n-octyl methylene blue, chemically, 3
n-octyl, 2,8 tetra methyl diaminothiazonium chloride:
This procedure is a combination and modification of
several procedures on preparation of methylene blue,

(8,

33, 34, 38).

12.2

grams

(0.1

mole) of pure dimethylaniline are

dissolved in 37*5 grams of concentrated HCL (30$) and allow­
ed to cool.

The solution is cooled with ice to 12-15°C.

During a one hour period 7.35 grams ( .145 mole) of

100/S

NaNOg are run in as a 20$ solution (delivery tube beneath
the surface of the liquid) taking care that the temperature
does not rise above 15°C.

The nitrosation is completed in

four hours.
Add 55 grams of 30$ HCI & 100 grams of ice.

17*5 grams

of good quality Zn dust is added during a quarter-hour per­
iod with mechanical stirring.
below 25°C.

The temperature must remain

(The amount of Zn dust added must be sufficient

to completely neutralize the HCI).

The solution is now

either colorless or a clear red color.

Neutralization is

complete when Congo paper is no longer turned blue.

The

solution is filtered and the Zn. dust is washed with very
little water.

86
At this point, it is essential that the substances he
added quickly and in the correct temperature*
The following solutions are made up at this point :
Solution I « 19 grams pure AlgCSO^)^ in 30 cc. H^O.
Solution II = 26.3 grams crystallized Wa 2S 203 in 25 cc* of
h 2o.
Solution III = 28 grams Na2Cr203 made up to 45 cc*
Solution IV s 10 grams n—octyl dimethylaniline in 13*5 grams
of strong HC1.
Solution V = 12.5 grains very finely powdered manganese diox­
ide*

Made up into a paste with 15 cc. H20.

To the p-aminodimethylaniline solution add 2 grams con­
centrated B^SOji^ and 50 grams of 5 0 p nonreducing AnCl2 solution.
Place the beaker on a felt pad and heat by blowing in steam.
Add solution I at the ordinary temperature with good stirring.
Add solution II, and after 2 seconds, one-third of solution
III.

Haise solution temperature to 40°G in one minute by

passing in dry steam*

Add solution IT and remainder of solu­

tion III and heat rapidly to 70°C.
solution V and heat to 85°C.
and cool to 50°C*

Once 70°C is reached, add

Hold at 85°C for one—half hour

Add 35 grams concentrated HgSO^.

Cool with

ice bath for 36 hours and filter off product with a little
10/» brine*
To obtain Zn-free product of n—octyl methylene blue,

dissolve the crude n-octyl methylene hlue in H^O-alcohol
mixture and add enough HagCO^ to completely precipitate all
the Zn present,

filter the solution.

25 grams of HG1 solution.

Add

75

grams salt and

Let solution stand and cool in salt

and ice hath until precipitation is complete and then filter.
The above procedure is given in equation form in Table A.
The key to the preparation is equation

which yields the

n-octyl thiosulphonic acid of indamine.

The test and proof

of the n-octyl methylene blue is given in the discussion sec­
tion*

88

L C U f r r i O N S FOR P R L l ftfxh Tf OE O F
A L / < y i - S U D 5 T / T U T t . p E / E T r / L L / V E E l U €.

C/r 3 n-CCT/Lj 2 , 8 Tf.rEE E'i_ r F y L
e / e / ' I / z f o r / --/c TLO/v/or/ r CEErrr.-- s > e

No. 2
CHj

ch5

CHj

Ni '

CH£

N
i
-+ A/* N O
/-/-/

0

O f M £ r w VL

N~G

fit. fLI N L
'

■ .'■?- rj: Cor. £

D / n o rn

fl/ui.

No. 2
C //-r
v - /
i

CH,

c/v*
s J /
N
i

*

1- 7 r>
I
N=£

I f'.F'f’ "fiMl

P f 9/r/r - E / T O C C O

'■ < £ T n / „

ot n £ 7h yl r ////./a/a

N

fr

No. 3
C H -<

N

7 /v3

CHf

✓

/V
i

N
y Ni-r \ £ $ > o - $

N H
E / 9 Of) ■

>
N>t _

_

( O O L, triC J

;■

m

p

Tfi&LE

E

<■■:

- */>C.N/C. Of C /D

/9/*7/A/o o ) N £ r n ZL

Of

/JEJ

l

INC

89

No. 4
- NH 2
Ch$

n

v

c h 3/

A /»

-tf

-S -SO^H

f (N *lCrt2 *7 ) CH3 pj
CHj

■CW5

Th icpsc/lp h o m /c P\C!D

o-ocrrt &/rte.r*yL

of p - o t n c T H f L

/?<v/i//vr

'CHS

/7 -OCT/L TH IOSULPHOs^'/C
ftCI Q Of /ftOf /“7 /A-'£

fAfti. /rJ£

N o . 5^

n - o c r ft. fp>,'o-

He!

-Ca H t?

/,■£O j

s>e/i. p >h oss 'C h c /j j +

Of /At&rt/H/Mf

£

C

{A/eur/TH l )

_

i
N-

CH2 '

~

n-eCTVL

,'CHs
'CHl— c l f H ^ N

MELTH LE M L

E>L(sf

G O i . ;/ T I o / J

No. 6
n - oci

zn

/1

+ 1 £ />/ l £ /v f

:<ct iT / a,\/

3L Uf

+

cf2

V"\

&
/V M

C

I

w

N s hj7
-n ,c LLl
%CHJ

2 IM G c'/*LT o f n- OC. r /■

/7£ r// /Z Z A/Z P t/f
TH B

l

t

H

90

N o. 7

z /N C StfL-r

A/&2 C 0 j

/ 7 f 7 - / y ^ £ / v £ GALAS' t
S

Oc. i/T/ O/V

Z n C&j +
^

&

m e

t h

/ l E a /£

(/£ /a / s o l u t i o n

H ZO

/Vo. 6

l- octvl
S>i.L>E

He /

h e ehl e n e

EOLL'Ttart

•Cq H n

+

,c h 3

-N.

A /* £ /
CHs

kc h

7

r>-0£. rye M E 7 tri £7lE C>t U E ^ 3
n-CCr/L £ ? 6 ) 7-E-rKrt M E T H y L

n

Ts9C3a£

?

’y o r ?-tto z ^ / V /^y/V c tilor<*4at

/?
M

91
The preparation of the 3 n-octyl 2,8 tetra methyl diaminothiazonium chloride depended on the ability of preparing
ortho n-octyl dimethyl aniline.

Table 3 gives reactions A

to F which show the reactions used to convert benzene into
ortho-n-octyl dimethyl aniline*
React ion A.

Benzene to n-hentyl phenyl ketone.

This reaction was brought about by a Friedal-Craft reac­
tion between the benzene and n-capryl chloride.
This chloride (43» 77) was prepared by reacting 2 mols of
n-caprylic acid with an excess of thiony chloride (i.e. 3 mols).
Equipment used was a three neck flask equipped with reflux
condenser, stirring mechanism, dropping funnel and thermometer.
After the thionyl chloride was refluxing, the acid was added
drqpwise.

After complete addition, the solution is boiled

and allowed to stand for eight hours.

The n-capryl chloride

is vacuum fractionated and refractionated.
at 81-82° at 16 mm.

The cut was taken

The yield was 72/».

The Friedel-Craft reaction employed was a modification
of the method used by Wood & Associates (45).

Twenty-five

mols of benzene are placed in a three neck flask equipped as
for the chloride preparation above.

The flask was cooled

with an ice-salt mixture and kept at a 10°C while 4.3 mols of
aluminum chloride was added.

This low temperature was main­

tained while 1.5 mol of the n-capryl chloride was added over

92
a three and one-half hoar period*

The temperature is raised

and when hydrochloric acid ceases to evolve the temperature
is lowered.
The reaction is kept cool for ten hours, after which time
the whole mass is poured on acidified crushed ice.

After five

hours, the organic layer i3 separated and the excess benzene
distilled off.
The n-heptyl ketone is washed three t imes with a sodium
carbonate solution, and then three times with water, dried and
subjected to a vacuum fractionation and refractionation.

This

reaction gave a yield of 83$ of the normal product whose boil­
ing point was l6l°Il at 20 mm.
Reactions,

n-hept.yl phenyl ketone to n-oct.yl benzene.

This reaction was carried by the use of a Modification of
the V/olff-Kishner Reduction (42).

This is an improved proce­

dure over the Clemmensen reduction method (4?, 53)* the modi­
fied procedure consists in refluxing the carbonyl compound in
a moderate amount of diethylene or triethylene glycol with 85$
hydrazine hydrate and about three equivalents of sodium or
potassium hydroxide for one hour, distilling enough water and
excess hydrazine to raise the temperature and then refluxing
the solution for several hours longer.
In this case, 1.0 mol of n-heptyl phenyl ketone was placed
in a round bottom flask to which had been added 120 grams of

93
£QUf>TlON

C£

£3/0

0/07 H O

TH£L

R i ? £.

£ T /O N

n -OCTYL f?/V/L/NC

fo'E-PO 7/6 / v £
s

NC

C 7 H/ S

I

fi/c/x
C-7” lS C^
r\-! £ £>£/.

n -H£ r-Ty L - K£- ~CN£

H £ H Z . t \>L

/ Of OCT i ON

13
fg"/7
W O L F F - £ t z - h ' N B. R
+■

+■

J P ^ i '' V
n -h

e

C C T 7 l. -

P i '/

h p h z e

: A/

7'r>//£

k£hCTlO!

+•H ^ O

*-///V." ?
£■U PH//; H I ”£ ’/ £

n OCTVL £

//-'Z

ft 2 I O

GXTmC -n -CCTYL

/■/£

N //"/?<9 £ £ /v Z u :V £

T f i t

L

b

.

3

9^
R E / ^ C r / C F v

D

f- H J7
fl Hg HC I

C h -*OS-/

HCLyFQ

c
/Vvr . r c

HH/L fN €

g £ .v ::£ /Vt

R E A C T I O N

H iDFOCH LCfi.7D£

£
V
?©
6(
/V/7

- Nhp

K'H.C
+- N f\ O H

*

'

0

o re TM o n - CC T i L
f'i rJiL .'/V£ H >••/. •
;: r

/■-L- F i C T I Q N

m

•_' ,v / £.

Ft N t L I N EL

F

■C H r

JH .

- N
"C H

£>A'JT H O ’ n - C C r /£ -

7" /

/':•!M L T H Y L

Ft /v /£ /A/£.

THB L £

£>

FtAT/ L //V£

95
potassium hydroxide, 1000 cc. of triethylene glycol and 100
cc. of 85$ hydrazine, then the entire mixture was refluxed for
two hours.
The aqueous liquor was removed hy means of a take-off
adapter until the temperature of the liquid rose to 150 de­
grees.

Re fluxing was then continued for five hours, after

which period the reaction mixture and aqueous distillate were
comhined, and then extracted with ether and then neutralized.
The neutral organic fraction was distilled over sodium.

A

yield of 60$ of n-octyl "benzene was obtained, boiling point
of 135-137 degrees at 20 mm.
Reaction 0.

n-octyl benzene to ortho n-octyl nitro benzene.

The production of an ortho nitro group was very difficult,
since most nitration methods give substitutions in the octyl
group.

Furthermore, any method of nitrating n-octyl benzene

which places a nitro group on the benzene ring are all chief­
ly para and meta directing.

The method used (65) was the

best one found in the literature however, the yield of the
pure ortho octyl nitrobenzene was discouragingly low.
One mol of n-octyl benzene was placed in a three necked
flask equipped as for capryl chloride preparation.

TWo hun­

dred fifty cc. of fuming nitric acid is added dropwise while
the temperature is held at 10 degrees,
approximately six hours.

^lie addition takes

The reaction product is poured on

96
crashed ice and extracted with *K)0 cc. of "benzene.

She or­

ganic layer is washed three times with sodium carbonate solu­
tion and three times with distilled water.
The benzene is distilled over at atmospheric pressure.
The remaining material is subjected to vacuum fractionated
and refractionation.

The yield is only 13$ of the ortho com­

pound whose boiling point was 181-182° I1 at 20 mm.
Reactions D and E.

Ortho n-octyl nitro benzene

to ortho n-octyl aniline.
In the method used (76) Oroggins C^t-O) gives many of the
reactions, properties of analine and its derivatives.

Two

hundred and fifty cc. of methanol are placed in a three neck­
ed flask equipped with a stirrer and reflux condenser.

To

the flask was added 0.5 mol of ortho n-octyl nitro benzene
and then 10 cc. of concentrated hydrochloric acid.

The en­

tire mixture was refluxed and 90 grams of iron filings were
added, 20 grams at a time, refluxing over one-half hour inter­
vals was then continued, for three hours.

Potassium hydroxide

is used to neutralize the excess hydrochloric acid.

The

residue can then be filtered hot and the methanol is distilled
over.

Hydrochloric acid is then added.

The mixture is sub­

jected to low temperature and the hydrochloride of the ortho
n-octyl aniline can be filtered off.

The hydrochloride is

changed to the ortho n-octyl aniline by potassium hydroxide.

97
She ortho n-octyl aniline is extracted with ether.

She

ether is then distilled off and organic material is sub­
jected to a vacuum fractionation and refractionation.

A

yield of 65$ of ortho n-octyl aniline was obtained its
boiling point was 169-171° at 5 mm.
Reaction E.

Ortho n-octyl aniline to ortho n-octyl
dimethyl aniline.

Dimetbylation can be carried out by using methanol and
sulfuric acid.

However, the modified procedure (7» 73) em­

ployed in this case involved the use of dimethyl sulphate
which was available.

Extreme precautions were necessary due

to the severe action upon the mucous membrane.
A three neck flask was used which contained the same
equipment as for reaction A.

Extra care was taken to insure

proper venting of the apparatus.

One—half mol of ortho n—

octyl aniline was added to the flask along with 0.6 mol of
calcium hydrate which is finely powered and thoroughly dried.
0.7 mol of dimethyl sulphate is added slow enough to keep the
temperature below 80 degrees,
minutes.

This addition takes about 60

She mixture was then refluxed for ten hours and ex­

tracted with ether.

The excess dimethyl sulphate was frac­

tionated off and the ortho n-octyl dimethyl aniline subjected
to vacuum fractionation.

The yield was 67$ with a boiling

point of 181-183° at 10 mm.

This ortho n-octyl dimethyl aniline was used in the pre­
paration of n-octyl methylene "blue as given in Tahle A.

It

should "be pointed out that many of these reactions were carried
out numerous times to obtain workable quantities of the de­
sired materials.
sults.

The yield, etc. or based on the average re­

The quantities used were those found by trial and

error to give the best amount with the better yields necessary
to produce a workable quantity of n-octyl methylene blue.
GRAVIMETRIC DETERMINATION 01’ ZINC SILICATE ORES (32)
Treat 0.5 g* of the finely ground ore in a covered
casserole with 10 ml. of 12 M hydrochloric acid, heating
gently until all violent action is over; add 5 nil. of 16 M
nitric acid and 5 ml. of 18 M sulfuric acid and digest on
the hot-plate until the ore is completely decomposed.

Eva­

porate to copious fumes of sulfuric anhydride in order to
expel all traces of hydrochloric and nitric acids, but take
care not to go to dryness; allow the solution to cool, and,
after estimating the amount of sulfuric acid which remains,
add 50 ml. of water and enough more sulfuric acid to make
the total concentration of acid about 1.5 to 2 M.

Introduce

into the solution a piece of sheet aluminum about two inches
square and bent up at its corners, and boil for about 10 min­
utes —

this will usually serve for the complete reduction to

the metallic state of any lead, copper, arsenic and antimony

99
that might "be present, hut any cadmium or bismuth will be
only partially reduced,

Filter the solution through a filter

paper in which is placed a piece of metallic alluminum, and
receive the filtrate in an Erlenmeyer flask.

After washing

the filter four or five times with small portions of hot
water, cool the filtrate and washings to room temperature,
add several drops of methyl orange indicator, and neutralize
with 15 M ammonium hydroxide; now add enough hydrochloric
acid to make its concentration in the final volume equal to
0,3 M, heat the solution to 80° -90°, and pass in hydrogen
sulfide to precipitate any cadmium or bismuth and any traces
of copper.

After the precipitate has settled, filter it off

and wash with 0,3 M hydrochloric acid saturated with hydrogen
sulfide.
After the precipitate has been filtered and washed with
0.1 M formic acid, which is saturated with hydrogen sulfide,
it is transferred to a weighed porcelain crucible and the
filter paper is charred, preferably by standing the crucible
upon a quartz plate, which is heated strongly by means of a
Meker burner.

The ignition of the filter paper is very slowly

and carefully completed in an oxidizing atmosphere over a
Bunsen burner.

The reaction should proceed only to the for­

mation of AnSO^, anfl not to ZnO.

If the reaction proceeds to

ZnO, the subsequent moistening of the residue with concentrated

sulfuric acid often generates heat enough, so that the water
which is formed according to the reaction, ZnO+HgSO^

^O-t-ZnSOij,,

is converted into steam, and particles of the precipitate are
thrown out of the crucible.

After cooling, the precipitate

is carefully moistened with a few drops of 9 M sulfuric acid,
and the crucible is heated in an air-bath until the excess
acid is driven off, then heated over the Bunsen burner to re­
move any charred material*

The precipitate is again moistened

with concentrated sulfuric acid and the crucible heated in the
air-bath, until the excess of acid is driven off; it is
allowed to cool, then weighed; the moistening with sulfuric
acid and subsequent evaporation is continued to constant
weight, two such treatments usually being sufficient.

A blank

is run to correct for any impurities in the reagents, and the
residue (usually about 0*2 mg) is substracted from the final
weight of zinc sulfate.
NOTES ON METHODS OF PRECIPITATION
After the insoluble sulfides of the tin and copper groups
have been filtered off, the filtrate can be used for the
separation of the zinc from cobalt, nickel, iron and manganese
by precipitating the zinc as sulfide after the acidity has
been adjusted to a value of pH ** 2.1.
follows:

The procedure is as

The filtrate from the hydrogen sulfide precipitation

of the copper and tin groups (copper having been previously

101
removed lay electrolysis or electro-deposition.) is evaporated
to a volume of 125 ml* if the volume is greater than this
amount.

It is then freed of hydrogen sulfide hy boiling in

a 750 ml. Erlenmeyer flask until the escaping steam no longer
smells of hydrogen sulfide; the solution is cooled to room
temperature and 6 M ammonium hydroxide is added until the
precipitate which first forms just fails to redissolve.

25 ml.

of 1 M citric acid (200 g. citric acid per liter) are added,
also a few drops of methyl orange indicator, and then 6 M
ammonium hydroxide until the solution Is neutral to the methyl
orange.

If the solution has not been previously cooled, the

methyl orange will be rapidly destroyed by the hot solution
anfl its use would be unreliable.

The prior removal of the

hydrogen sulfide is also essential, as this agent destroys
methyl orange.

25 ml. of “formic mixture*1 is next added, then

20 ml. of 24 M formic acid, after which the volume of the
solution is made up to 200 ml.

This procedure is necessary

in order to establish the right concentration of hydrogen ion
for the precipitation and at the same time to provide a buffer
to hold the concentration of hydrogen ion sensibly constant
during the process of a precipitation.
"S’ormic mixture*' Is a solution of the following composi­
tion:

200 ml. of 24 M formic acid (Sp. G-r. 1.20), 30 ml. of

15 M ammonium hydroxide, and 200 g. of ammonium sulfate, made

4

102
up to one liter with distilled water.

The function of the

ammonium sulfate is to aid in "salting out" the zinc sulfide
in granular form as recommended by Treadwell in accordance
with the work of G. H. Kramers who also showed that ammonium
chloride or thiocyanate are equally good for this purpose.
Since zinc is usually precipitated as the sulfide from a sul­
fate solution in the analysis of an alloy or ore, the choice
of ammonium sulfate seems to "be the preferable one for the
"salting out" effect.
The flask containing the solution being analyzed is
placed on a wire gauze supported on a tripod and heated to
about 60°-70°.

Then a two-hole rubber stopper, having each

hole fitted with a glass tube which is bent at right angles
and which just passes through the stopper, is placed snugly
and securely in the neck of the flask.

One of the bent glass

tubes is connected by means of a piece of rubber tubing to a
wash bottle which contains distilled water and is connected
in turn with a hydrogen sulfide generator; the other glass
tube is equipped with a short piece of rubber tubing to be
subsequently closed by means of a pinch clamp.

After having

introduced the rubber stopper and having observed that the
exit tube is open, the hydrogen sulfide is allowed to flow so
as to displace the air in the flask and the heating is con­
tinued until the solution almost boils.

The burner is

103
removed and the exit tube is closed with a pinch clamp at
once, but the hydrogen sulfide supply is kept open and
connected with the precipitation flask.
frequently to insure complete saturation.

?he latter is shaken
V/hen the solution

has cooled to 25°-30°, the supply of hydrogen sulfide may be
turned off.

She precipitate of zinc sulfide, which should

be white in color, will usually settle within thirty or forty
minutes and will be ready for filtration.

It often happens,

in the process of precipitation, especially when the flask
has not been thoroughly cleaned, that a layer of zinc sulfide
sticks so firmly to the sides of the flask that it cannot be
removed,

^he precipitate adhering to the flask is then

dissolved in hot dilute sulfuric acid (2-3 ml. of 18 M sulfur­
ic acid in 25 ml. of water), just neutralized with ammonium
hydroxide, or better, neutralized and then made slightly acid
with formic acid, saturated with hydrogen sulfide under
pressure, heated to boiling to coagulate the precipitate, and
filtered through the filter containing the already washed
precipitate of zinc sulfide.

Ihrther, washing is unnecessary,

as aiy salt or acid present is volatile.
Ihe precipitate of zinc sulfide is filtered through an
ashless filter paper and washed thoroughly with 0.1 M formic
acid saturated with hydrogen sulfide.

104
Polarogatophic Determination of Zinc in Zinc Silicate Ores on
FISHER EhECTROPQpE (73)
In order to give a "basic check on "both the volumetric and
gravimetric method for analysis of zinc in the various silicate
ores, the polarog§©phic method was used.

The ore was prepared

the same as in the volumetric method up through the addition
of KCLO^ and subsequent filtration,
procedure section).

(See volumetric method in

Prom this point on aliquot portion could

be taken and subjected to the following procedure:
Take suitable aliquot to dryness.
of 0.2 U HC1.

Cool and add 25 ml,

Heat just to boiling, and transfer by filtering

into 50 ml, volumetric flask containing exactly 5*0 ml. of
internal standard which is at a temperature of 25*0°C., and
five drops of broracresol purple.

Wash filter paper with re­

peated portions of distilled water to approximately 45 ml.,
add 1.0 ml. of gelatine, and make to volume at 25,0°C.

Trans­

fer 10.0 ml. aliquot to polarogSfephic cell, add three drops
(0.05 ml.) of concentrated ammonium hydroxide and polarize at
l/50 sensitivity (S » 5Q2C) from 1000 x 10""*^ to 1700 x 10"”-^
volts.

The zinc concentration will then be determined from

the ratio obtained in plotting this portion of the curve.
Gelatine Maximum Suppressor:

A fresh solution contain­

ing 1.0 gram of U.S.P. granular gelatine per 100 ml. of
distilled water is prepared.

Use 1.0 ml. of this solution

105
per 50 ml* of solution to "be polarized.
Bromcresol Purple Indicator:

A 0.1 percent solution is

made "by mascerating 0.1 gram of dry 'bromcresol purple powder
in a mortar with 18.5 ml* of 0.01 IT NaOH and diluting mixture
to 100 ml. with distilled water.

Use 5 drops per 50 ml. of

solution to he polarized.
Oxygen Absorbent for Purification of Nitrogen:

Pass

nitrogen through a first scrubbingflask containing a solution
of ^+0 ml. NH^OH, ^K) ml.

saturated with NH^Cl (approxi­

mately 25 grams), and filled with copper gauze, especially
in the air spaces; then, through a second scrubbing solution
of dilute sulfuric acid (5^0 •

106

B IB L I 0 S E A P H Y
1.

Andreeva, A. P., Tsventye Metal, 2., 46-50, (1940).

2.

Arnold, G., United States Patent (June 8, 1937)•

3.

Barsch, 0., Kolloid Chem. Beihefte 20, 1 (1924).

4.

Barth., 0., Die Mellallverfluechtigungsverfonren mit
hesonderer Beruech suhtigung der Herstullung von
Zinkexyd 1935» Vilhelm Knapp, p. 117-147.

5.

Bunge, S'. H,, Pine, M. M. and Legsdin, A,, University
of Missouri School of Mines and Metallurgy, Bull.
Vol. 17. 3* (1946).

6.

Ibid., p. 17

7.

Cade, I., Ghem. and Met. Eng. 2£, 319» (1923)*

8.

Gain, J. G. and Thorpe, J. F., The Synthetic I>yestuffs
and Intermediate Products. Charles Griffin & Company
Limited, London, p. 289, (1923)•

9.

Committee on Uniformity in Technical Analysis, J* Am,
Chem. Soc. 26, 1648 (1904).

10,

Cottermole, British Patent 777*283*

11,

Crabtree, E. H. Jr., Eagle-Pitcher Co., Private Communica (1952).

12. Dana, E. S., A Text-Book of Minerology, John Wiley & Sons,
Inc. Hew York, p. 422, (1916),
13.

Ibid, p. 466

14.

Ibid, p. 360

15.

Dean, H, S. and Ambrose, P, M., United States Bureau
Mines, Bull. 449, P» 71 •

16.

DeVaney, E. D., United States Patent 2,410,021 (Oct.
29, 1946).

107
17*

DeVaney, 3?. D., Picklands, Mather and Co., Private
C ommunica (1950).

18.

DeWitt, C. G., Ind. and Eng., Chem. 22, 652, (19^0).

19.

DeWitt, C. C., and Ashabhai, P. I., 2-^-6 Trihydroxyphenyl Alkyl Ketones as flotation Peagents Por Manganese
Dioxide, M. S. Thesis, Michigan State College, 1951,
30 numb, leaves.

20.

DeWitt, C. C. and Botchelder, P. von., J* Am. Chem.
Soc. 61, 12^7, (1939).

21*

DeWitt, C. C* and Brown, M. G-., An Alkyl Substituted
Triphenylmethane Dye as a Plotation Agent for Stibnite, M. S. Thesis, Michigan State College, 1950,
23 numb, leaves.

22.

DeWitt, C. C. and Lenton, P. A., Proth Plotation of
Azurite and Maluchite in Alkaline Barth Gangue Ma­
terial, M. S. Thesis, Michigan State College, 19^3,
4-0 numb, leaves.

23*

DeWitt, C. C. and Livingood, M. D . , Plotation of Copper
Silicate by Selected Alkyl Substituted Pooyhydroxy
Bitroso Phenols, Ph. D. Thesis, Michigan State College
1951, 12^ numb, leaves.

2^.

DeWitt, C. C. and Ludt, P. W., The Plotation of Copper
Silicate by Alkyl-substituted Triphenyl Methane Dyes,
Ph. D. Thesis, Michigan State College, 19^7, 95 numb,
leaves•

25*

DeWitt, C. C. and Makens, P. P., J . of Am. Chem. Soc.
iit, W , (1932).

26.

DeWitt, C. C. and Overcash, P. L., Separation of Seeds
by Proth Plotation, M, S. Thesis, Michigan State
College, 19^2, 51 numb, leaves.

27.

DeWitt, C. C. and Thakkar, J. L., Alkyl Substituted
Wurster's Salts as Plotation Peagents, Thesis, Michi­
gan State College, 1950, 28 numb, leaves.

28.

Dow Chemical Co., Plotation Pundamentals 2nd Ed. Dow
Chemical Co., San Prancisco, P. 7»

108
29. Edser, E., British Assn. for Adv. of Science.
report on Colloid Chemistry 4;, 263 (1922).

Eourth

30.

Erlenmeyer, H . , Steiger, J. V. and Theilheimers, W.,
Helv. Chem. Aeta., 25., 24-1-5 (194-2).

31.

Eahrenwald, A. W., Eng. Mining J., 14-6. 155 (194-5).

32.

Eales, H. A. and Kenny, E., Inorganic Quantitative
Analysis. D. Aopleton - Century, N. J., p. 317*
(1939).

33.

Eierz, David, H. E., Translated hy E. A. Mason, Eundamental Processes of Dye Chemistry, J. A. Churchill,
Londo*., 1st. Ed. p. 174—177 (1921).

34-.

Eierz, David, H. E. and Blangey, L., Translated hy P. W.
Vittum, Eondamental Processes of Dye Chemistry, Inter­
science Publishers, Inc., New York, 5th Ed., p. 311
(194-9).

35.

Ibid., p. 392.

36.

Eoulk, C. W., Koll. Zeitsch, 6o, 115 (1932).

37*

Eorment, A., British Patent, 12778 (1902).

38.

G-eorgievics, G. V. and Grandmougin, E., Translated by
E. A. Mason, A Text-Book of Dye Chemistry* Scott,
Greenwood & Son, London, p. 201, (1920).

39*

Grandnougin, E., Chem. Zeit., ^KXXVI., 1167, (1912).

4-0.

Groggins, P. H., Aniline and Its Derivatives.
Nostrand Co., New York, (1924-).

4-1.

Gutzeit, G., United States Patent 2,125*631 (Aug. 2,
1938).

4-2.

Haung-Minlow, J. Am. Chem. Soc. 68, 2488 (194-6).

4-3.

Helferich, B. and Schaefer, V/., Organic Synthesis
Conant, J. B. ed., New York, John Wiley & Sons,
Vol. 9, P. 32, (1929).

44-.

Hoover, T. J 0, Mining Magazine, London (1916).

D. Van

109
45.

Ju, T. Y., Shen, G. and Wood, G.E., Shen, G., Inst.
Petr. 514, (1940).

46.

Seller and Lewis, United States Patents 1,554,216 anfl
1,554,220.

47•

Knecht, E., J. Soc. Dyers, 6 , XIX, (1903).

48.

Knecht, E., and Hihhert, E., New Reduction Methods in
Volumetric Analysis, 2nd Ed., Longmans, Green, London
(1928).

4 9. Kohmann, S. P., and Johnson, 2?. B., J. Am. Chem. Soc.
26. 1259. (1914).
50.

Lessel, V., Concentration Engineer International Smelt­
ing and Refining Co., Private Communica (1950).

51.

Loomis, P. B., Pield Book of Common Rocks and Minerals.
Tenth Impression, G. P. Putnam's Sons, New York and
London, p. 67, (1923).

52.

Ihid., p. 68

53*

Martin, E. E., Organic Reactions, Adams, R. ed., New
York, John Wiley & Sons, Vol. 1 , p. 167, (1942).

54.

McKenna, W. J., Lessel, V. and Peterson, E. J., United
States Patent 2,482,859 (Sept. 27, 1949).

5 5 . McDonald, W. T., Eng. Min. J. 126. 679 (1928).
56.

Nieto, J. C., Legsdin, A. and Schlechten, A. W., Bull.
School of Mines and Metallurgy, Univ. cf Mo. Vol. 18,
No. 4, p. 3, (1947).

57.

Petersen, W., Schwimmaufbereitung, Steinkopff, Dresden
and Leipzig, p. 221 (1936).

58.

Ihid., p. 228.

59.

Phillips, P. C., An Introduction to Crystallography,
Longmans, Green and Co., London, New York, Toronto,
p. 120 (1946).

60.

Ihid, p. 112

61.

Ralston, A. W., and Pool, •/. 0. .United States Patent
2,168,849, (Aug. 8, 1939).

110
62.

Ralston, A. W., and Pool, W. 0., United States Patent
2,267.307, (Dec. 23, 19^1).

63.

Rex, H. J., 3ng. Min. J. 1*»2., 69. (19*18).

64.

Richards, R. E. Asst. Chief Chemist., Tennessee Copper
Company, private communica, (1950)*

65-

Rinkes, I. J., Rec. Tray. Chem. 63, 3, 53, (1944).

66.

Schwartz, A. United States Patent 807,501 (1905).

67.

Scott, W. P., Standard Methods of Chemical Analysis,
D. Van Rostrand Co., Vol. 1, p. 106?, (1939)*

68.

Siegmund, Monatsh, Chem. XXXIII, 1431, (1912).

69. Sisley, Bull. Soc. Chem., 862, (1901).
70.

Sulman and Picard, United States Patent 962,678 (1910).

71.

Taggart, A. P., Taylor, T. C. and Ince, C. H . , A.I.M.E.
Technical Publication 204, (I929).

72.

Ullman, P., Diese Berichte 2, 33, 1900, p. 2476 .

73.

VonParowe, D., Private Communica, (1950).

74.

Wark, I. W., Principles of Plotation, Australasian Inst.
Min. and Met., Melbourne, Australia (1938).

75.

Weinig, A. J. and Carpenter, G. B., The Trend of Plo­
tation, Quarterly Vol. XXXII No. 4 (Oct. 1937), Colorado
School of Mines, p. 21.

76.

West, R. J., Chem. Soc. 122.,

77.

Weygand, C., Organic Preparations, New York, Inter­
science Publ., p. 101, (19^5).

78.

Wilson, L. A., Chief of Testing Dept., New Jersey Zinc,
Private Commanica, (1950).

(1925).