ane

PN

 
 

  
 

tM

lh

|

60
Ion |
LC O

 

 

 

aa a
1
1

 

MEIC k- moll
Spraying Substances
en Oh)

io] Oa
HESIS
“PRAY TnG SUn SATAN C

Flovd ‘". Qven,

7
My
=a «- 6 e

v2

Cleass '02,
yHESIS
10821
“PRAY ING SUESTA

mT
2
ty
i)

Flovd “', Owen.

Spraying consists in covering plants, or parts
of plants, with a thin uniform film of liquid capable of
destroving or preventing an attack of some particular
parasitic organism. A spraying substance must possess
poisonous, caustic or offensive qualities and should
possess a suitable physical structure. ‘he first nemned
properties have received much attention; the last named
have received little cr none. The Object of this study
is to discover the most suitable physical structure of
one class of spraving substances--the arsenites.

“More definitely the materials with which Ii
have worked are: White arsenic, Faris green, pure arsenite
of lime, Londen purple, and a few ersenoids. The method
of work with each was:--To examine the prysical structure
under a compound microscope; to measure tne diameter
of the particles with a microewmillimeter scale; and to
determine the time of suspension in water. In the case of
the arsenoids, chenical analvses for white arsenic were

alsc made. In testing the times of suspension, 1.295 frs.
-~2..

of an average sample of the material to be tested was
added to 25 ce of water ina tall graduate. After vigor-
ous shaking, tne mixture was allowed to rest until all of
the sediment had reacned the botitom, tne time required
tnen being noted. Several ordinary samples of each sub=
stance were examined in the ways mentioned, and by repeat-
ing tests of each one, quite accurate comparisons were
Obtained. Sarmles of white arsenic and paris freen were
pulverized in a glass mortar, in order to compare the
time of susrension of the smaller particles with that of
the ordinary material,

An inquiry as to the relation existing between
the diameters of small particles and their times of sus-
pension, brought the following from the U. S. Department
Of Agriculture, Division of Soils:

"ine theoretical rate of settling of small
particles of spherical form in water would be, with the
conditions the same, directly as the radii of the particles.
You will see that this would follow from the fact that
the mass varies as the cube of the radius, while the effec-
tive surface--in this case the cross=sectiocn of the sphere
through the center--varies as the square of the radius.
Consequently, if one particle was twice the diameter of
tne second, it would settle twice as fast. This relation
does not hold, however, for irregular particles and it
has not been possible to obtain a definite relation between

the mean diameter of the particles and the rate of settling.
~-2.-

of an average sarinle of the material to be tested was
added to 25 ce of water ina tall graduate. After vigor-
ous shaking, the mixture was allowed to rest until all of
the sediment had reacned the botitom, the time required
tnen being noted. Several ordinary samples of each sub=
stance were examined in the ways mentioned, and by repeai-
ing tests of each one, quite accurate comparisons were
Obtained. Sarples of white arsenic and paris freen were
pulverized in a glass mortar, in order to compare the
time of susrension of the smaller particles with that of
tne ordinary material.

An inquiry as to the relation existing between
the diameters of small particles and their times of sus-
pension, brought the following from the U. S. Department
Of Agriculture, Division of Soils:

"The theoretical rate of settling of small
particles of spherical form in water would be, with the
conditions the same, directly as the radii of the particles.
You will see that this would follow from the fact that
the mass varies as the cube of the radius, while the effec-
tive surface--in this case the cross-section of the sphere
through the center--varies as the square of the radius.
Consequently, if one pazsticle was twice the diameter of
tne second, it would settle twice as fast. This relation
does not hold, however, for irregular particles and it
has not been possible to obtain a definite relation between

the mean diameter of the particles and the rate of settling.
tre variations in surface conditions is undcubtedly lar; ely

responsible for the irrerularities that are observed."

meen eC - - ~ - - - - - -- = _ = . ~ - - se - - ae -— = ~-

utr mY m1 Ts
SPST EG Ts

“nis ordinarily cecurs as a clear, white,
tasteless, odorless powder, slightly soluble in water
and cormosed of sinell octahedral crvstals whose chenical
composition is AS, 0,» Under the microsccrne, I fcund
the particles to be of variaile forms and sizes; to have a
semi-transparent arrearance; and to ran:i.e in their
diameters from 0.0033 mm. to 0.033 mm., the averare heinr
0.0266 rm. The susrension of an ordinary sample tested
as above described, was three minutes; of a pulverized
sample, 5.9 to 6 minutes,

PARIS GREE.

Under the microsccpe, Paris frreen was found to
he cormosed of smeil, auite uniform rreen spheres with a
diemeter ranging from 0.0135 mm. to 0.025 mm. Of ten
samples which I examined, all contained a quantity of
small, semietransrarent particles, a snail rortion of
which was impurity. In a few sarmles crystals of free
white arsenic could he distinruisned, thouph tne microscope
was net fourd to he reliable in determinin: very accurately

whether the arount was injurious or not.
 
-~-4--

A nicroscopic cormarison of lime and the immurity found
in most of the arsenites indicated that free lime was fre-
quently present. There was also often seen particles of
avery finely divided raterial which did not resemble
Paris green spheres, and yet may be a form of aceto-
arsenite of copper in which the chemical action was not
quite complete. This is easily mistaken for impurity.

Aside from a chemical analysis--really the only
conclusive teste-the most satisfactory method proved to
be the compound microscope which almost certainly decid-~
ed a sammle to be pure or adulterated, and with some
experience, an approximate estimation of the quantity
and quality of the impurity could be made. By this means
crystals of water=- soluble arsenic were detected, and
anything not pure Paris green was readily seen. Different
lots of this substance, however, were found to vary a
great deal in their structure, so that the size of the
spheres was never the same, and yet, uniformity toa
high degree in any one sample can be expected.

The suspension of the ten samples was examined
in the way indicated and found to vary from 3.5 to 4
minutes; of a sample pulverized to a condition in which
the color was midwav hetween white and the freen of the
Ordinary substance+-the particles averaging half the
diameter of those of the original material--the time was
6.5 to 7 minutes. Cne freat fault of Paris green is its
shcert time of suspension, end were it necessary, tne mater-

tal could he pulverized in a mill, thereby losin, its
2 ee oe eye

 

 
woe -_ ow

green cclor and becoming white. Rut correspondence with
manufacturers indicated that it is not cnly possible but
is much easier for them to make a product of much smaller
particles than thcse of the ordinary size, and that it
is only customary to produce the larger crvstals--such
material having a deeper, richer green, and being, they
say, what the trade demands. Such a peris green would
certainly possess the advantages of the ordinary, and yet
oe capatle of remaining a longer time in suspension. It
Would be fur easier to apply, and more effective, uniform
and economical in its results.

PURE ARSRUILTE OF LIME,

Sarples of this were made by boiling white
arsenic, One part, and unslaked lime, two parts by
Weight. ‘These were tested by acidifying with hydrocloric
acid and then subjecting to hydrogen sulphide, any trace
Of free arsenic being precipitated as the yellow sulphide
Of arsenic. Frrom tie tests, I found that both should be
hoiled torether and for at least a half hour as the lime
in dissolving combines with the arsenic and forms a very
poisonous, but insOluble, and sc a perfectly safe spreving
compound,

A dry sample of the pure arsenite of lime is
a fine, grayish white powder. which , microsccpically, was
seen to be Of simple structure, the particles bein:
granular, scmewhat transparent, exceedinzgly variable in

size, and irregular in shape. Measurements were fcund
impracticable. An examination showed its time of sus-

pension to be five minutes.

ee eee mmm me

Fight sarmlies of London purple were collected
from various dealers, and examined. Highly magnified,
tne purest sample was seen to consist of irregularly
shared bodies of mostly small though widely different
sizes, the surface of the larrer particles beinr rough
and uneven. Sone had merely a dull purple color, while
Other masses--under a certain focus--were reddish purple
and had a brilliant metallic lustre. All samples contain-
ed foreign matter in varying anounts, much of which exist-
ed as very fine particles with no resemblance to London
purple, but corresponding to some of the impurity found
in Paris green. Small, rectangular or stick-shaned bodies
which were transparent were also occasionally detected.
‘Measurements proved impracticable,

une susvension of tne samples ranged frcm twelve
to fifteen minutes, which fact accounts for the little
apitation this substance requires and its consequent
ease Of application,--the probable explanation of the
popularity London purple held for a time rerardiess of
its frequent injury to foliare. The buoyancy of the
particles is evidently due to their extraordinary irregul-

arity and large surface for a small bulk, these combined,
providing the material with a floatins power.

AR SA® "OID -«,

Six or tre so-called "Arsenoids", manufactured
by the Adler Color and Chemicel Works of New York, were
examined. The first--"lo. 2"--is a whitish green powder.
Under the microscope, the particles were very smail (some
were barely visible) and adherent, forming small masses.
Mxcept for the presence of some free arsenic, very littic
impurity was seen. The suspension of this arsenoid was
six minutes. A chemical analysis fave 23,457% of total
AS, 05 » the mest of which was combined with copyer, a
smai1 tnougn injurious portion being free.

"Yo. 3" arsenoid microscopically contained two
principle substances. Tne first consisted of small,
transparent, dJrregulariy shaped particles, some of which
were grantilar; the second of darr colored bodies but
Otherwise like the first. Some crvstals resembliny those
of paris green were also seen and as the cnemical exeamina-
tion showed ccpyer to be present, true Paris green was
believed to be an ingredient. No free white arsenic was

distinguished. Tre arsenoid's time of suspension was

e > e aA on
four minutes. An analysis showed only 14.9277, of As, 0;
none Of Wnich Was free, a quantity of lead, and a trace cf

coprer and bisriutn.
Arsenoid "Vo. 4" had a distinct freenish tinre, and under
the microsccre, consisted cr the sare smatil, irrecular
particles es the anove. Some soluble blue--round blue
bodies of variable sizes--and a quantity of ¢reen material,
evidently Paris freen, were noted. This sample remained
in suspension six minutes. Chenically it contained
56.491 o> totel arsenic, some copper, and the nost free
arsenic of amv sample.

Besides the small sized perticles above mentioneg
mo. O" contained a larre amount or Teris frreen ora
Similar arsenite or copper. Its time or susnension was
the lonrest of all, being, seven minutes. 64,727% of total
AS, Cg were found, entirely too much being free however.
Copper was also present.

The last arsenoid , "io. 6", differed from the
above only in beinrs of a lighter color, containing less
copper and less free arsenic, and havin: a total content
of 65.6937 of As,0,,--entirely too much of the latter
heing free. Its time of suspension was 6.5 minutes.

"Green Arsenoid" is a@ plain arsenite of co

ty

ITeY,
chernically resembling Paris rreen except that the acetic

acid is eliminated. Jticrosconpically it was found to he «a
very finely divided material, almost free from foreirn

matter. Its susrension was eight minutes--more than twice

In conclusion IT hone to rave shown thet the value of
 
a spravin,g substance depends somewhat upon its physical
struccure and tne size cof its particles, and how much
attention this snould raceive from both manufacturer
and sovrayer. We are in great need or cheap and reliable
arsenites--tnose made up of very minute particles and
having a sufficiency of combined arsenic, a long time of
Suspension, absolute insolubility in water and a freedom
from free arsenic and other impurities.
Lastivy I wish to acknowledse many valuable
sursestions in the work from Professor U. P. Hedrick
Cf the Collese.
So UM ™*A RY,
I. The physical structure of spraying: substances is
very important and in great need of inmmrovenent.
Il. Spraying substances with particles of much finer

divisicn would favor:

9

In tne manufacture--especially of
paris green.

ry
e

In original cost to the sprayer.

1. HKeonom. Less bulk required for a given

surface to be covered.

ue

required afitation and trouble from
cloceead macninery.

In applicetion--by lesseninz; the

NNO TE ONTOS ONO
e

a9

Lonser suspension insures preater
uniformity in strensth of filn.

ps
\—
e

2. hffectiveness. omiller particles insure a more
conplete distribution of poison

for a siven anount.

O)

onaller particles adhere better
to foliare.

I ey yf
~-19--
nO T MN. The physical structure and time of sus-
pension of Bordeaux Mixture made under verious conditions

wes studied put the results were not conclusive.

--= o- Ce ee ee ed - - - - - - - -_ = -= - - = -_ «=

The following sets forth crephiecilvy a compari-

son of the examination:

EEE Comosition
Substance'Susrensi- 'tAver.dia. TTotal MOther inrredients
‘on in min.'of partic."As 0 '
ns i Te “2 Te ee
Write ' ' ' ’
arsenic ' 3. 1.0266 mi. T1005 ’
' ? ’ :
“nite Ars! ' ' '
pulver, ' 5,5 Mreas.irmr.' " ’
t t t q
Paris ' ' ' ,
erzen ' 0O--4 ',018 rm, ' 58.455 "Oud = 31.29;0 4 Cy
' ve ido 2
? t t t
Paris er.' ' ' '
pulver. ' 6.5--7 'lieas. impr! ’ " "
f ’ t t
Arsenite ' ’ ’ '
of lime ' 5. ro "  ' Cal. arsénite.
f ? ! t
London ' , ' '
purple r1e.--15. ' " " ' Cal.ars.} arsenite and
' ' ' ' residues.
t ? t t
"ITO. oN ? f g f
arsenoid ' 6. ‘ "153.45", rou.
f 8 t t
"To. jf t t t t
t ! ? ?
arsencid ' 4. ro" nm 914.9275, *' Ph. Cu. Pi.
f f ’ t
WO e 4 ! t g !
arsenoid ' 6G. ro "156,491". ' Cu.
t ? t g
MITO, 5" ? t t t
arsenoid ' 7. ro "964,727, ' Cru.
t Y t !
"ITO. G6" t ? ? t
: a 4
arsenoid ' 6.5 rou " 163.6935 !' Cu.
1 t t t
"orcen 9 ? f a
arsenoid"™’ 8, ro "ot ' rlain arsenite
| of conrer, |
 
a
>
>=
—
wT
3 =———e
—"
=r
oS
—nr
& ——=

wt

|

3

IM