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COMIBUTIONS TO ELECTROSTATIC DUSTING:
I. APPLICATION OF POLAROGRAPHY
TO BUS? DEPOSIT EVALUATION,

2. EFFECT OF :omzao CURRENT
INTENSITIES AND EFFECT os
SHIELDING ON DUST DEPOSITION

Thai: for the Dog!“ 05 M. S.
MICHIGAIKI STAW ‘JHNERSITY
Nguyen ‘E'u Ban
I955

CONTRIBUTIONS TO ELECTROSTATIC DUSTING:
1. APPLICATION OF POLAROGRAPHY
TO DUST DEPOSIT EVALUATION,
2. EFFECT OF IONIZED CURRENT
INTENSITIES AND EFFECT OF
SHIELDING 0N DUST DEPOSITION.

By
Nguyen Tu Ban

K

AN ABSTRACT

Submitted to the Michigan State University of
Agriculture and Applied Science in partial
fulfillment of the requirements for the
degree of

MASTER OF SCIENCE

Department of Agricultural Engineering
Year 1955

Approved by jULJCLQIZl.YK, CliifiLiég

6: Nov. “If:

 

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a Nguyen Tu Ban ”
l

The ultimate goal of the project on dusting and spraying,
of which this study is a part, is the increase in efficiency
of deposition and uniformity of coverage of plant surfaces
by pesticides. The means to this goal is the utilization
of electrostatic field forces.

The specific topics covered by this study are: the
application of polarographic analysis to the problem of
dust deposit evaluation, the effect of ionized current in-
tensities on dust deposition, and the use of an external
electric field to increase dust deposition.

A Sargent Model III, manual type, polarograph was used
to measure the copper concentration of hydrated capper sul-
fate dissolved in an aqueous solution. An electrolyte com»
posed of 0.h M potassium sulfate and 0.01 percent gelatin,
was found suitable for the evaluation of copper sulfate dust.

Copper concentration as low as 1 ppm was readily measured
in standard solutions prepared in the laboratory.

The polarographic method of evaluation was then applied
to the measurement of copper sulfate dust deposits on soy-
bean leaves after field dusting. Five square inches of
leaves -- ten square inches of leaf surface -- were punched
into a wadlsolution containing potassium sulfate. The solu-
tion was then brought to the laboratory and analyzed polaro-
graphically. The method of evaluation was found satisfactory,

both for the field work and for the laboratory experiment.

Nguyen Tu Ban
2

The field tests on soybean plants showed, in general,
no difference in dust deposits between well-exposed leaves
and hidden leaves.

Electrostatic dusting appeared better than the conven-
tional method of dusting, although the increase in deposition
was not as great as expected.

The effect of current intensities, and the effect of
shielding,were studied in the laboratory at sixty percent
relative humidity. The shield, made of one-quarter inch
hardware screen, was placed parallel to the dust collector
disc. A potential of 20 RV was applied to the shield to
produce the external electric field. Four dusts were used,
and the deposits evaluated by weighing with an analytical
balance.

The results showed that for the micronized copper sul-
fate, the Attaclay and the Attasorb, the dust deposits in-
creased greatly -- as many as ten times -- with increased
current intensities up to 150 microamperes. With further
increases in the current, the increase in dust deposition
was negligible.

Standard copper sulfate followed the same trend as the
other dusts. It showed a great increase in deposition around
500 microamperes, and a sharp decrease at 600 microamperes.

Below and up to current intensities of 50 microamperes,

shielding improved the deposition of standard copper sulfate and

Nguyen Tu Ban
3

Attaclay, coarse dusts. Above 50 microamperes, the bene-
ficial effect of shielding disappeared.

Shielding greatly improved the deposition of the
micronized copper sulfate, but it decreased the deposition

of Attasorb.

CONTRIBUTIONS TO ELECTROSTATIC DUSTING:
1; APPLICATION OF POLAROGRAPHY
To DUST DEPOSIT EVALUATION,
2. EFFECT OF IONIZED CURRENT
INTENSITIES AND EFFECT OF
SHIELDING ON DUST DEPOSITION

BY

Nguyen Tu Ban

A THESIS

Submitted to the Michigan State University of
Agriculture and Applied Science in partial
fulfillment of the requirements

for the degree of

MASTER OF SCIENCE

Department of Agricultural Engineering
1955

ACKNOWLEDGMENTS

This study would not have been possible without the
assistance of many individuals:

To Dr. W. M. Carleton of the Department of Agricultural
Engineering, for his patient guidance, the faith he had in
the author which was most helpful in facing difficulties
with assurance,

To Professor A. W. Farrell, for granting the research
assistantship,

To the Rackham Foundation, for providing financial
support,

To Dr. Andrew Timnick of the Department of Chemistry,
for his guidance in the polarographic work,

To.Dr. D. J. Montgomery of the Department of Physics,
for his valuable advice on the conduct of the research,

To Dr. W. E. Splinter and Mr. R. N. Brittain for ac-
quainting the author with electrostatic dusting,

To Mr. B. A. Stout, Mr. W. Bilanski, Mr. L. F. Sander-
son, Mr. S. L. Hedden, Mr. Pio Angelini, and Mr. T. Kinjo,
for their valuable assistances in the taking of data,

To Mr. Nuredin Mohsenin for some of the photographic

work,

To Mr. J. B. Cawood and his assistants for their
patience in familiarizing the author with the mechanical
tools,

To the Attapulgus Minerals and Chemicals Corporation
for contributing the Attasorb,

To Miss Alfreda Abell for her unselfish interest in
the author's work, and her constructive criticisms during
the writing of the manuscript,

To the above-mentioned and to many others, the author
humbly takes this opportunity to express his most sincere

thanks e

 

133......(‘9- .5,(..14r . ,.

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TABLE OF CONTENTS

PAGE

INTRODUCTION 0 O O O O O O O O O O 0 O O O O O O 0 0
Historical Background for the Study . . . . . . .

The General Problem . . . . . . . . . . . . . . .

4?de

The Specific Problem . . . . . . . . . . . . . . .

THE APPLICATION OF POLAROGRAPHY TO THE EVALUATION OF
PBSTICIDAL DUST DEPOSITS ON PLANT SURFACES . . . . . .
BackgrOund for the Study . . . . . . . . . . . . .
Definition of Polarography . . . . . . . . . .

O‘O‘O‘Vl

Theoretical Principles . . . . . . . . . . . .
Polarograph Circuit . . . . . . . . . . . . . l3
Polarogram . . . . . . . . . . . . . . . . . . 13
Equipment and Procedure . . . . . . . . . . . . . 18
Laboratory Investigations . . . . . . . . . . 18
Calibration Curves . . . . . . . . . . . . . 21
Results . . . . . . . . . . . . . . . . . . . 26
Laboratory Dust Deposit Evaluation . . . . . . . . 2b
Scope of the Polarographic Method . . . . . . . . 27
FIELD TESTS TO STUDY THE FEASIBILITY OF THE POLAROGRAPHIC
METHOD OF DUST EVALUATION . . . . . . . . . . . . . . . 26
Description of Equipment . . . . . . . . . . . . . ZO

Dusting Equipment . . . . . . . . . . . . . . 26

TABLE OF CONTENTS (Cont.)

Dust Evaluation Equipment . . . . . . . . . . .
Plot Design and Procedure . . . . . . . . . . . . .
Discussion of Results . . . . . . . . . . . . . . .

Merit of the Polarographic Method of Analysis .

Dust Deposits Analysis . . . . . . . . . . . . .

Comparison of Top Leaf and Hidden Leaf Deposits.

Analysis of Variance . . . . . . . . . . . . . .

Dust Deposit Efficiency . . . . . . . . . . . .

THE EFFECT OF THE IONIZED CURRENT INTENSITIES AND THE
EFFECT OF SHIELDING ON DUST DEPOSITION . . . . . . . . .
Experimental Equipment and Procedure . . . . . . . .
Laboratory Dust Chambers . . . . . . . . . . . .
The dust feed Chamber . . . . . . . . . . .
The dust feed mechanism . . . . . . . . . .
The dusting chamber ... . . . . . . . . . .

Charging Nozzle . . . . . . . . . . . . . . . .

Electrical Circuit . . . . . . . . . . . . . . .

Electric Shield . . . . . . . . . . . . . . . .

Operating Conditions . . . . . . . . . . . . . .

Experimental Design . . . . . . . . . . . . . .

EXperimental Procedure . . . . . . . . . . . . .
Discussion of Results . . . . . . . . . . . . . . .

Millipore Filter Dep031ts e e e e e e e e e e e

Page
30
3O
36
36
36
37
ul

LLS
Le
as
us
as

TABLE OF CONTENTS (Cont.)
Page
Effect of Current Intensities . . . . . . . . 60
Effect of Shielding . . . . . . . . . . . . . 61
SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . 67
APPENDIX A - PARTICLE SIZE DETERMINATION . . . . . . . 69
Review of Literature . . . . . . . . . . . . . . 69
Equipment and Technique . . . . . . . . . . . . . 71
Sampling . . . . . . . . . . . . . . . . . . 71
Counting . . . . . . . . . . . . . . . . . . 71
Results . 3 . . . . . . . . . . . . . . . . . . . 72
Average Diameters . . . . . . . . . . . . . . 7;
APPENDIX B - EXPERIMENTAL RESULTS . . . . . . . . . . . 62
REFERENCES CITED . . . . . . . . . . . . . . . . . . . 91

LIST OF FIGURES

FIGURE
1. Schematic diagram of an electrolysis apparatus .
2. Current-voltage relationships with (B) polarized
and (D) unpolarized electrodes . . . . . . . . .
3. Schematic diagram of polarographic circuit . . .
h. A typical polarogram . . . . . . . . . . . . . .
5. H-type cell and saturated calomel electrode . . .
'6. Polarograph assembly . . . . . . . . . . . . . .
7. Polarogram of copper sulfate . . . . . . . . . .
8. Calibration curves of copper sulfate . . . . . .
9. Rear view of experimental duster . . . . . . . .
10. Side view of experimental duster . . . . . . . .
ll. Plot design for field tests on soybeans . . . . .
12. Sampling technique . . . . . . . . . . . . . . .
13. Dust deposits on soybeans as a function of rates
of application . . . . . . . . . . . . . . . . .
lh. Dust deposit variation . . . . . . . . . . . . .
15. Dust feed chamber . . . . . . . . . . . . . . . .
16. Feed end of dust feed mechanism . . . . . . . . .
17. Inside of dusting chamber . . . . . . . . . . . .
.18. Dust collector disc and electric shield . . . . .
19. Two types of charging nozzle . . . . . . . . . .

PAGE

. 9

LIST OF FIGURES (Cont.)

Inside construction of a single support type

C O O O O O O O O O O O O O

Nozzle charging apparatus . . . . . . . . . . . .

Average Millipore filter deposits . . . . . . . .

Charged currents versus applied voltages . . . .

FIGURE
20.

charging nozzle . .
21.
22.
23.
2h. Average dust deposits
25. Average dust deposits
26. Linear measurement of
27. Objective scale . . .
28. Size-frequency curve
29. Size-frequency curve
30. Size-frequency curve

versus current intensities
versus current intensities

particle . . . . . . . . .

O O O O O O O O O O C O O 0

PAGE

TABLE

I.
II.

III.

IV.
V.
VI.

VII.
VIII.
IX.
X.

XI.
XII.

XIII.

XIV.

LIST OF TABLES

Polarograph Calibration Data . .-. . . . . . . .

Average Values of Dust Deposits from Field Tests
on Soybean Plants . . . . . . . . . . . . . . .

Analysis of Variance of Dust Deposits on
SoybeanPlantB................

Dust Deposition Efficiency in Soybean Tests . . .
Charging Nozzle Performance . . . . . . . . . . .

Average Values of Dust Deposits Due to Charging
or Charging and Shielding . . . . . . . . . . .

Cumulative Size-Frequency Distribution . . . . .
Average Diameters and Densities of Dusts . . . .
Part1C13 3128 Data 0 e e o e e e e e e e e 0.0 0

Data of Field Tests on Soybeans Dusted with
Standard Copper Sulfate . . . . . . . . . . . .

Millipore Filter Deposits . . . . . . . . . . . .

Data Showing the Current-Voltage Relationships
During Ionization . . . . . . . . . . . . . . .

Results of Tests on the Effect of Current
Intensities and Shielding on Dust Deposits . .

Arithmetic Mean of Dust Deposits on Dust
COIlOCtOPDiscseeeeeeeeeeeeeeee

PAGE

25

39

AZ
UN
52

66

79
80
81

83
8h

85

87

89

INTRODUCTION

In man's struggle for survival there is the fight
against insects, fungi, and weeds, which destroy or hin-
der the production of his food. The most used weapons in
the battle against these foes are sprayers and dusters.

Brodell, Strickler and Phillips (8) report that, in
1952, in the United States alone, about 29 million acres
of farmland were sprayed or dusted an average of 2.86
times -- the equivalent of one treatment on 83 million
acres -— to combat insects and diseases, at a total cost
of about 193 million dollars.

The application of these pesticidal materials at
present is inefficient. Bowen (5) estimates that only ten
to twenty percent of the dust discharged by dusting machines
is actually deposited on the plant surfaces. Sprays are
somewhat more efficient. According to Splinter (20), fogs
are less efficient. It is apparent then, that any signi-
ficant increase in the efficiency of deposition of pesti-

cides would mean a considerable saving to the farmer.

Historical Background for the Study

In the belief that crop dusting is basically more

sound economically than spraying, Bowen (5), in 1950,

initiated the present research project in an effort to im-
prove the efficiency of dust deposition, and the uniformity
of coverage on plant surfaces, through the use of electro-
static field forces.

The work accomplished by Bowen, Hebblethwaite, Brazee,
and Brittain, and the history of the project are reviewed
by Splinter (20).

Splinter (20) discusses the influence of particle size
on the effectiveness of an insecticide or a fungicide, the
various forces affecting dust deposition, and the results
of laboratory and field work. His results were:

1. In general, reduction in particle size of pestici-
dal dusts increases the effectiveness against insects and
fungi. The smaller particles were also found less subject
to erosion by rain.

2. An equation was derived with which, it is believed
there can be calculated the effect of changes in application
rate and in particle size, on the control of plant diseases
and insects.

3. Of the forces considered -- gravitational, inertial,
thermal, and electrical -- only those due to an electric
field, caused by charged particles in an ionizing field,
were found to be of potential importance toward effective

deposition of fine dust particles.

35:1!»17‘1O viii; ¢.. 1
_ ,

 

The General Problem

The ultimate goal of this research project, is the in-
crease of deposition and uniformity of coverage of plant
surfaces by pesticides. The means to this goal is the
utilization of electrostatic field forces.

The application of electrostatic charging to the de-
position of pesticidal dusts, or, in short, electrostatic
dusting, gave extremely satisfactory results in the labora-
tory under controlled conditions. The field work, conducted
only on an exploratory scale, has not fulfilled the eXpec-
tations of the investigators. Extensive field tests have
not been planned to date. It is believed that, before fur-
ther field work is undertaken, it will be worthwhile to make
systematic investigations in the laboratory to provide a
sounder understanding of this problem.

Among the topics still to be considered are the effect
of resistivity of plants, the development of accurate meter-
ing devices for dust at very low rates, the development of
a fast, reliable and accurate method of evaluating dust de-
position on plant surfaces, the effect of the dilution of
the dust-air stream from the nozzle by surrounding air on

the dust cloud potential, and the superposition of an elec-

tric field on the field induced by the dust cloud itself.

11‘ Inlll’lll. 31‘1“. . .d w or . HLH. I: in“
n . ...;\~ 3.1
i ‘5'.

The Specific Problem

This study was conducted to investigate specifically:
first, the application of polarographic analysis to the
problem of dust deposit evaluation; second, the effect of
the ionized current intensities on dust deposition; and,

third, the use of an auxiliary electric field to increase

dust deposition

THE APPLICATION OF POLAROGRAPHY TO THE EVALUATION OF
PESTICIDAL DUST DEPOSITS ON PLANT SURFACES

Pest control by dusting depends, in the main, on two fac-
tors: coverage, and retention of the pesticidal dust. For
effective protection, plant surfaces must be well covered with
dustl, but what this means quantitatively is still unknown.
Hebblethwaite (1952) says:

It is unfortunately a fact that at the present

time biologists are unable to give a clear definition

of what constitutes "100 percent coverage" and there-

fore the engineer is in the difficult position of

not knowing what his goal is.

The degree of protection is customarily evaluated bio-
logically. This method of evaluation is not always desirable
because of the uncertainty of, and the time lapses between,
infestations, especially in investigations on the methodology
of dusting. The research worker requires a much more rapid
method of evaluation, even though it may be less complete.

It is only in the final analysis that he will need biological
evaluation in the form of field trials. Many workers in the
past have resorted to indirect methods of evaluation, either

physical or chemical. The chemical evaluation seems to be

prevalent (leaf printing to study the problem of distribution,

 

11n this thesis "dust" will mean pesticidal dust.

ashing and titration for quantitative analysis, and others).
Although methods in use may be accurate, a great deal of time
is required to perform the evaluation itself.

The following work was done in an attempt to provide
the workers in electrostatic dusting at Michigan State Uni-
versity with a fast, but accurate method for the evaluation

of dust deposit.

Background for the Study

Definition of Polarography

The polarographic method of chemical analysis, invented
by Jaroslav Heyrovsky in Prague about 1920, is based on the
unique characteristics of the current-voltage curves ob-
tained from the electrolysis of electroreducible or electro-
oxidizable substances in a cell at a dropping mercury elec-

trode.

Theoretical Principles

The basic principle upon which polarography depends,
is the production of concentration polarization. To illus-
trate this, and the salient facts pertaining to polarography,
consider the electrolysis apparatus shown schematically in
Fig. 1. Assume that the electrolytic cell contains a very
dilute solution of thallous chloride (say 0.001 M) in a

relatively large concentration of potassium chloride

 

gliruesh, «.51. SW, 1 le.--di,r. 2‘“
a, v ‘.. .
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(e.g., 0.1 M). Because oxygen is easily reducible, and

its reduction current more or less masks the current of

other substances, the cell is provided with a gas delivery
tube through which nitrogen or carbon dioxide is passed to
remove dissolved air from.the solution. C is a short length
of platinum wire which serves as the indicator electrode.

The other electrode P is a silver-silver chloride electrode
whose area is large enough so that it remains depolarized
when a small electrolysis current is passed through the solu-
tion. An electrode is said to be polarized when it adopts
the potential externally impressed upon it with little or no
change in the rate of the electrode reaction, i.e., no

change in current. The electrode C is of this type. 0n the
other hand, a depolarized electrode is one that retains a
constant potential regardless of the magnitude of the current.
The silver-silver chloride electrode in 0.1 M potassium
chloride behaves in this case very nearly like a depolarized
electrode when the current density is small. When an ex-

ternal emf is impressed on this electrode the reaction
Ag+Cl-:AgC1+e

will proceed either to the right or to the left depending

on the polarity of the emf applied. The potential is governed
by the concentration of chloride ions, and because this con-
centration is relatively large, it changes only slightly with

changes in current when the current density is small.

 

If the chloride ion concentration were made very small

5

e.g., 10- M, then even a relatively small reduction current
would increase the chloride ion concentration markedly, and
the potential of the silver-silver chloride electrode would
change considerably to correspond to the change in chloride
concentration at the electrode surface. This phenomenon is
commonly called concentration polarization.

Suppose now that an emf is applied to the cell in Fig. l
in such a direction that the platinum.e1ectrode is made nega-
tive with respect to the other electrode. The solution is
well stirred to minimize the changes in thallous concentration
at the surface of the platinum microelectrode. The current-
voltage curve obtained is indicated by OAB in Fig. 2. From
0 to A, the current remains very small. When the potential of
the platinum.electrode has been made equal to the decomposi-
tion potential of the thallous chloride in solution, (point

A), a further increase in applied emf causes the reduction of

thallous ion at the platinum electrode,
4.
T1 + e = T1

and correspondingly the current increases rapidly. In other
words, at point A or beyond, the platinum microelectrode is
depolarized by the reduction of thallous ions. with in-
creasingly applied emf, the current increases linearly in ac-
cordance with Ohm's law. The slope EVI would give the resis-
tance of the solution in the cell.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

J IL
' l
G
C P
6905 inlet
L__]
Fig. 1. Schematic diagram of an
electrolysis apparatus.
B
.9—
<2
w
t
3 D
k)
0 Applied emf‘

Fig. 2. Current-voltage relationships with
(B) polarized and (D) unpolarized
electrodes.

10

Suppose now that the experiment is repeated without
stirrigg the solution. The current, instead of rising in-
definitely according to Ohm's law after the decomposition
potential is reached, eventually, levels off and becomes
constant. This behaviour is illustrated by the curve OACD
in Fig. 2.

As the potential of the small electrode is made more
and more negative, the concentration of thallous ions at the
electrode surface is continually decreased. At point C the
thallous ion concentration at the electrode surface is
negligibly small compared with that in the bulk of the solu-
tion. A further increase in the applied emf from.C to D can
no longer appreciably decrease the thallous concentration at
the electrode surface. The platinum electrode is then in a
state of virtually complete concentration polarization, and
the current can no longer increase because it is determined
by the rate of diffusion of thallous ions from the bulk of
the solution to a region of practically zero concentration.
This results from the depletion of the thallous ion concen-
tration at the electrode surface by the electrode reaction.

The region CD is called a diffusion current region. Be-
cause the rate of diffusion is prOportional to the difference
in concentration in the two regions between which diffusion
occurs, the diffusion current_i§_p;oportional to the concen-

tration of thalloug110ng in the bulk of the solution. This

ll

proportionality is the basis for quantitative determinations
by polarographic analysis.

In the above experiments, a relatively large concentra-
tion of non-reducible electrolyte (potassium chloride) was
added to the solution in order to minimize the electrical
migration of thallous ions. A non-reducible electrolyte
added to an electrolysis solution in polarography is called
a "supporting electrolyte". The rate of electrical migration
of thallous ions depends on their relative concentration as
compared with the concentration of potassium chloride, and on
the transference numbers of thallous and potassium ions.

A transference number measures the fraction of total
current carried by a given ion in a solution (17).

When the concentration of the supporting electrolyte
is much greater than that of thallous chloride, the trans-
ference of thallous ions is reduced to practically zero, and
the current through the solution is carried almost entirely
by the ions of the supporting electrolyte. The transfer of
thallous ions to the cathode is then made entirely by diffusion,
and the diffusion current is said to be diffusion controlled.
If the electrical transference is greater than the diffusion
current. The difference between the two is called
the migration current (16).

Because,-in many ways, the polarographic method of

analysis bears resemblance to the electrolytic method, some

12

of the fundamental differences between the two methods are

tabulated as follows:

 

Method,
Parameters

Polarographic

Electrolytic

 

Electrodes
(for electroreducible
substances only)

Cathode: Dropping
mercury electrode
or rotated micro-
electrode.

Anode: Mercury pool
or saturated calomel
electrode (reference
electrode).

Cathode and
Anode:
Platinum.or
mercury
electrode

 

Currents measured

 

 

 

Variables Current or
measured with increasing voltage
applied emf. constant
Concentration Low limit 10-6 M. All concen-
range . trations
Depletion of electro- Practically Complete
reducible substance unaltered.

 

Duration

Short, usually a
few minute s .

Until comple-
tion of electro—

chemical reaQLiQ .

 

 

Current conduction
between electrodes

 

By migration of
supporting electro-
1yte ions through
solution, and by
diffusion only to
the electrode.

 

Migration
and
diffusion

 

 

13

In the interests of simplicity and clarity, the fol-
lowing discussion includes only electroreducible substances,
thus the repetition of the two terms "electroreducible"

and "electrooxidizable" will be avoided.

Polarograph Circuit
The electrical circuit used is very similar to the one
for electrolysis, a schematic diagram of which is shown in
Fig. 3. (For electroreduction an increasing negative emf is
applied between the electrodes by varying the resistance R.
The current for each applied emf is measured with a galvanometer

G. The plot of current against voltage results in a polaro-

grmm, Fig. u.

Polarogram

The limiting current (i) is the total steady current
measured (Fig. h). The limiting current is reached when the
reducible substance is reduced as rapidly as it reaches the
electrode surface and its concentration at the electrode
surface remains constant at a value that is negligibly small
compared to the concentration in the body of the solution.
Under these conditions, the current is independent, within
certain limits, of the applied emf and is governed wholly by
the rate of supply of the reducible substance to the elec-

trode surface from.the surrounding solution.

Golvonometer

@

 

 

{v}

Mercury R
Cathode
‘ F

9/; Electrolyte

 

 

Il'r.

emf.

 

|
HI

 

 

 

 

\

 

 

 

 

 

Anode

Fig. 3. Schematic diagram of polarographic
circuit. .

flush-.1553 .I.§.n...7n. Me 1. .L .r I. m5?» .. .L “4‘
.\

I’v‘

lll

Deflection

Golvonometer

 

15

\ .
, \ Mammum

 

    

l i—‘- ”I ”-

i

l

, i
Half Wave 3 i
Potential “X id i

'Limiting

Current, i

 

 

Fig. A. A typical polarogram.

16

0f the many factors influencing this current, four of the

most important are:

1.

2.

3.

The residual current (1r): usually very small
and approximately proportional to the applied
voltage, caused by traces of electroreducible
impurities;
The 'maximum?, a transitory and erratic current,
the origin of which is not completely understood,
but which is eliminated by the introduction of a
surface-active material or charged colloids, e.g.,
gelatin;
The migration current due to electrical migration
of the reducible ions which is eliminated by the
addition of an indifferent or supporting elec-
trolyte in a concentration of at least 50 times
that of the reacting material; (see page 11)
The diffusion current (id) which indicates the
concentration of the material being reduced.

1d 8 i - ir
The diffusion current depends on temperature,
viscosity, the ionic strength of the solution,
and the characteristics of the polarizable elec-
trode. The influence of these factors can be
seen in the Ilkovic equation, derived for the

dropping mercury electrode for constant temperature:

17

id = 607nD1/20m2/3 t1/6

where id is the average current in microamperes
during the life of a drop of mercury, n the

number of Faradays, D the diffusion coefficient
of the reducible or oxidizable substance in square
centimeters per second, C its concentration in
terms of’millimoles per liter, m.the rate of

flow of mercury from the dropping electrode capil-
lary in milligrams per second, and t the drop

time in seconds (16).

This equation predicts a linear relation between the
diffusion current and the concentration, the most important
relation in practical polarography.

The half-wave potential is characteristic of an electro-
reducible substance in a known supporting electrolyte, and
serves as the basis for qualitative identification of the
substance.

To reiterate, quantitative polarography is based on the
complete concentration polarization (see page at» or the
depletion of the concentration of the electro-reducible
substance at the electrode surface by the electrode reaction
which results in a limiting current over a range of potential.

For a detailed study on polarography, the reader is re-
ferred to the two volumes ”Polarography" by Kolthoff and

Lingane (16). Excellent bibliographies of polarographic

18

literature may be found in the following references:

1. "Bibliography of Polarographic Literature," 1922-
l9h5. E. H. Sargent and Co., Chicago, 1950.

2. "Bibliography of the DrOpping Mercury Electrode,"
Leeds and Northrup Co., Philadelphia, 1950.

Equipment and Procedure

A Sargent Model III polarograph, of the manual type, was
used. The voltages and currents were read and recorded. These
values were then plotted to obtain the polarogram. The H-type
cells used were of a design (Fig. 5) suggested by Dr. Andrew
Timnick of the Department of Chemistry, Michigan State Univer-
sity. Saturated calomel electrodes served as reference
electrodes. The cathodes were of the dropping mercury elec-
trode type (Fig. 6). This type consists essentially of a
capillary glass tube supplied with mercury from a reservoir.

The apparatus was arranged as shown in Figure 6.

Laboratory Investigations

2 was selected as a dusting

Hydrated cOpper sulfate
material to be used both for the laboratory and the field
tests, because of its solubility in water, and because copper

is a common element in dusting materials.

 

2See Appendix A for specifications of the dust.

 

a E‘flllllulldiI-II-‘ I‘I $11533.“H
. s e
..I

. .l.
3“

19

 

F180 5

Left - H type cell
A - Agar plug
B — Saturated KCl and calomel solution
C - Solution for analysis

Right - Saturated calomel electrode

D - Agar bridge

E - Mercury pool

F - Saturated KCl and calomel solution
G - Electrode filled with mercury

In preparing the saturated calomel electrode,
care must be taken that the platinum loop at
the end of this electrode is well placed in
the mercury pool and that it does not touch
the calomel solution.

 

20

Emmawoamaom I m
deoE

Hamoumaaaaass I m

Hams meant: I a

 

. peace ammospaz I o
Aeposwv enoepomae aeSoaeo nepwadpem I m
Accoflpmov ouoapocac mqfidaoan Sanchez I <

”hansemmm squamoamaom

e .mam

21

The supporting electrolyte found most suitable for this
dust, was potassium sulfate at a concentration of 0.h M.

Gelatin, at a concentration of 0.01 percent, was very
effective as a "maximum" suppressor. Empirical calibra-
tion curves were then constructed by analyzing standard

solutions of known concentrations.

Calibration Curves

Because the calibration curves were constructed strictly
on an empirical basis, the following conditions were maintained
constant at all times, during the analysis for calibration
purposes and afterward during the evaluation of actual test
solutions:

1. Composition of supporting electrolyte,

2. Characteristics of the dropping electrode, i.e.,

constant m.and t values,

3. Concentration of maximum suppressor.

A standard solution of copper sulfate (Cu SQh' SHZO) was
prepared by dissolving 0.3928 gm of copper sulfate in water.
Enough water was then added to increase the volume to 100 ml.
The solution contained one milligram of metallic copper per
milliliter of solution or 1000 ppm. Subsequent known concen-
trations were obtained from this standard solution by dilution.

To eliminate the effect of the migration current, 0.h M
potassium sulfate solution was used as the supporting elec-
trolyte. Gelatin at a concentration of 0.01 percent was used

as the maximum.suppressor.

 

a 13.7. .1: .
. .

,3. Willi. <1 v. m
I

 

22

A 25-ml. standard solution containing 10 ppm copper
was analyzed, and its polarogram plotted (Fig. 7). This
plotting was a preliminary step in determining the half-wave
potential of copper in 0.h M potassium sulfate solution, and
also in finding the potential at which the limiting current
became steady. From this polarogram, the value of -0.u
volts was selected as the applied emf for routine analyses.

For routine analysis the complete plotting of the
polarogram is unnecessary. During the evaluation, only the
concentration of the reduced substance is measured, it being
the only variable in the Ilkovic equation, other factors
being held constant.

Subsequent standard concentrations were then analyzed
by bringing the applied emf immediately to -0.h volts and
recording the galvanometer deflections. that is, high and
low values from.which the average deflection was computed.
The emf was next brought to zero and the galvanometer de-
flections were again read and recorded. The second average
value was subtracted from.the first one, and the result used
in the plotting of the calibration curve. This was done to
minimize the error due to the drifting of the galvanometer
zero reading.

Calibration curves (Fig. 8) were constructed using the

data shown in Table I.

Galvanom eter Deflection _ Cm.

9.0

8.0

7.0

6.0

5.0

4.0

3.0

2.0

|.0

 

 

IO ppm
Half Wave Potential
I
: O ppni
l
i
I l 1 I I 1 J
—0.l -0.2 -0.3 -O.4 -0.5 -—O.6
‘ Applied emf —Volts

Fig. 7. Polarogram of copper sulfate
in 0.h M potassium sulfate and
0.01 percent gelatin.

 

 

all; DIRKI. )‘l e.» .n.1.l

 

Pr .

 

8.0

e I»
O O

CuSO4-5H20 in 25ml. Solution, Wt. in Mg.
n)
'O

 

O

 

SIO
$5
52
SI
1 i l 1 LI 1 l L l J
5 IO IS 20 25

Galvanometer Deflection in Cm.

Fig. 8. Calibration curves of copper
sulfate in 0.h M potassium.
sulfate and 0.01 percent
gelatin. Galvanometer reading
at 'Oeh VOlte

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a
8.3....éé 2.2 as 8.0 i“ as * Gus est:
0H.ea mm.ma am. a Nm.0 a . _ it
oo.oa a~.0a 00.ma we. oI ma.0 _ a m _ H am.o 0H
IIIIILII IIITIIIIIIIIIII I.II.I._TII..III
a» m0.m~t mm. mm Hm.ma sm.o _ _ . m:.0 omsss><
2 , .._l t
m0.0m
mm.mm mm.ma am.ma mm.0 .
0H.0m No.0H m:.~a . ma.e . m:.0 m
I I I I I hI I I I I I I 1 I I I I I I L! I I I v I I I." I. 4.- I I I I I
jRim ::.0a 0m.mH mm.0 a i .NH.H omssm><
mn.:~ a:.ma m0.ma mm.0 e i m0.a
ao.:m oa.ma . aa.ma m mm.H
m 0m.:~ ma.0a m0.ma 0:.w ~0.a m
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madamoaoas
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page sonnm
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. uneasbasvm
_ mo.sm 0:.ma 0a.a mm.m am.m mm.m owsuo><
m~.m
0m.m
oa.ma :0.m
00. mm 0~.ma on.» 0e.m 00.m oa.m
me. am 0m.na m0.» om.m om.m mm.m
mo. mm mmm.ma 0a.a am.m mm.m am.m a
oma mma 00H ma om 0: on mm om 0H m m.m a o_ essence
- , Quaa>auunemm
coaaaaz hem muacm ca coaueapcooaoo aoaaou Queuoaoca>aeo

 

 

muao> 3.0I as meanness .50 dd ecoavooamou acneaode>acw owaae><
zHe<Amw BZMQmMm do. 0 az< dommu z 3.0 2H ma<mnbm mmmmoo mo <B<Q 20Hs<mmHA<u mm<moommqom

H mumda

Instead of plotting galvanometer deflection as a function
of concentration, the weight of hydrated copper sulfate was
computed from the concentration in parts per million and
plotted as a function of the galvanometer deflection. In
this way, one reading of the calibration chart gave directly
the amount of hydrated copper sulfate in 25 ml of solution.

It should be noted that the galvanometer deflections re-
corded measured both the diffusion current and the residual
current. Evaluation of the diffusion current alone was not

necessary.

Results

Cepper concentration as low as one part per million
was readily detected. This sensitivity could still be im»
proved if rigorous temperature control was observed. Kolthoff
and Lingane (16) stated that the lower limit of polarographic
detection was in the neighborhood of 10"6 M. This is approxi-
mately equivalent to 0.06h parts per million copper concen-

tration, or 0.25 milligrams per liter of solution of the

hydrated cOpper sulfate used in this investigation.

Laboratory Dust Deposit Evaluation

Brittain utilized the polarographic method successfully
in his laboratory work on plant-leaf surfaces. The surfaces

were dusted with copper sulfate. The dust deposits were then

27

carefully washed off by shaking the leaves in closed Mason
Jars containing 211.5 ml of potassium sulfate solution, which
upon addition of 0.5 ml of gelatin solution, had a molarity

of 0.14.. These solutions were then analyzed polarographically.

For details, the reader is referred to Brittain's thesis (7).

Scope of the Polarographic Method

The polarographic method of analysis as applied to the
quantification of dust deposit is not restricted to copper
measurement alone. The method can be applied to any other
dusting materials, organic or inorganic, provided that a
suitable solvent and a good supporting electrolyte can be
found for each material, and provided that the substances

measured contain at least one element that is either reducible

or oxidizable .

l I.) .I I taillltl.IIIIIll1I. IIIIIIII.II

 

IIIII

 

28

FIELD TESTS TO STUDY THE FEASIBILITY OF THE POLAROGRAPHIC
METHOD OF DUST EVALUATION

When the method of dust evaluation with the polarograph
was finally worked out during the latter part of the summer
of 195,4: it was decided to test its feasibility in the actual
evaluation of leaf samples collected in field tests.

The field tests were carried out with this specific
purpose in mind and also to study the following:

1. To investigate the efficiency of electrostatic
dusting in depositing dust in "hidden" parts of plants.

2. To compare the deposition of conventional and elec-

trostatic dusting as a function of the rate of application
of dust.

Description of Equipment

Dusting Equipment

The field duster used was an adaptation of a Niagara
"Even Flow" Model AA machine. It was an eight-nozzle duster
equipped with a Niagara Evenfeed dust metering unit. The

power to drive the duster unit was supplied by a 7 H.P. Novo
One-cylinder gasoline engine (Fig. 9.).

29

 

Fig. 9. Rear view of experimental duster.

 

Fig. 10. Side view of experimental duster
showing charging equipment.

30

The charging apparatus consisted principally of a high
voltage tripler circuit connected to a 300-volt dynamotor
powered by a six-volt battery (Fig. 10).

A more complete description of the experimental duster

and the electrical circuit used will be found in Hebbleth-

waite 's thesis (12).

Dust Evaluation Equipment
7 The apparatus used is as described on page 18. The wash
solution for dissolving the hydrated copper sulfate dust de-
posited on leaf surfaces was prepared in large quantity by
dissolving 71.09LI grams of potassium sulfate (M. W. 1711.25)
in distilled water and making up the final volume to exactly
one liter. Half-pint Mason jars were filled with 211.5 ml
or this wash solution and taken out to the test plot. A
multiple-cell mount was constructed to allow the simultaneous
analysis of more than one solution (Fig. 6).

For sampling leaves, a leaf punch was built according
to the specifications of Smith and Little (19). It was pat-
t”oerned after an ordinary paper punch. The punched area

measured one square inch.

Plot Design and Procedure

A randomized block design was used to set up test plots.
The dusting was carried out on soybeans, planted in rows. 21+

inches wide and spaced 85 inches center to center. Soybeans

31

were chosen because they were the only crop available at
the time (September l95h).

The dust used was standard hydrated copper sulfate. Its
size analysis will be found in Appendix A. Three rates of
application were used. These rates were determined by directly
weighing the actual amount of dust output for each setting of
the duster feed cut-off. The rates of application were:

1. Low rate, 27.2 lbs. per acre,
2. Medium.rate, h2.3 lbs. per acre,
3. High rate, 68.2 lbs. per acre.

Only four central nozzles of the duster were connected
for electrostatic charging. The charging current was set at
75 microamperes for each nozzle. ,

The actual experimental layout of the plots is shown
in Fig. 11. A code for the various plot symbols was set up
as follows:

1. The first letter referred to whether the dust was
charged or uncharged (C and U respectively),

2. The second letter referred to the rate of appli-
cation (high H, medium.M, or low L).

In each case the treated rows were separated by untreated
rows to avoid contamination. Each plot measured fourteen
feet wide, and fifty feet long.

To assure uniformity and consistency for each treatment,

all the plots marked for the same treatment were dusted at

0
.A1

'illlllll

 

 

 

 

 

 

 

 

 

 

:Lectfigy 1' 3 S 7
I CL UL UH UM
II ‘UL. CM CL CM
III UM UM CH CL
IV CH CL CH UH
V UH CM UH UM
VI UL CH UM- CM

 

 

 

 

 

 

 

 

Fig. 11. Plot design for field tests on

CL
CM

Efifi

soybeans.

Charged, low rate
Charged, medium rate
Charged, high rate
Uncharged, low rate
Uncharged, medium.rate

Uncharged, high rate

LOW rate = 27.2 lbs. per acre

Medium.rate 8 u2.3 lbs. per acre

High rate = 68.2 lbs. per acre

 

one time. The samples were then gathered before the next
treatment was applied. In this manner, the duster was driven
more than once over each plot, but the immediate sampling
after each treatment eliminated the knocking-off of dust
from the leaf surfaces.

The sampling was done by laying a fifty-foot steel tape
along the row and gathering leaf samples at the row center,
at the 20th and at the LIOth foot mark (Fig. 12). Two types
of leaves were collected, the top leaf, well exposed to the
dust stream, and the lower "hidden" leaf. For each sample,
five square inches of leaf surface-n counting one side only
-- were punched into each Mason jar containing 211.5 ml of
wash solution. The jar was closed tightly and shaken imme-
diately to wash the copper dust deposit off the leaves.
Shaking for one minute was found adequate by Brittain (7)
to dissolve all the copper dust deposited. Blank solutions
were also included. These solutions were taken back to the
laboratory and evaluated polarographically for dust content.

The relative humidity during the whole test varied be-
tween 13.5 percent and 63 percent. The wind velocity measured
with a hot-wire anemometer was between 200 and 750 fpm. Most
°f the time its direction was at a right angle to the forward
direction of the duster. The dusting was carried out only
in one direction. At the end of each test row, instead of

going back in the opposite direction, the duster was driven

 

 

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g.
.‘; -—
’.
..
F
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35

back to the end of another row and the test run in the same
direction as on the first row.

For the routine evaluation of the solutions the fol-
lowing steps were taken in the laboratory:

1. 0.5 m1 of a one percent gelatin was added to the
Mason Jar; the solution then had a final volume of 25 ml,
containing 0.11 M potassium sulfate, 0.01 percent gelatin,
and copper at a concentration to be found upon analysis;

2. About 20 m1 of this solution was introduced into
the H-type cell;

3. Commercial oil-pumped nitrogen was bubbled through
for about 10 minutes to displace dissolved air;

14.. An emf of -0.LI volts was applied, the low and high
galvanometer deflections were recorded, and the average value
computed;

5. The emf was brought to zero, the new high and low
galvanometer deflections recorded and the average deflection
computed. This value was subtracted from the average value
Obtained in step [1,, and the resulting value used to find
the- amount of hydrated copper sulfate in solution from the
Calibration chart (Fig. 8).

With the aid of the multiple-cell arrangement (Fig. 6)
the operator was able to work on three samples simultaneously,

and thus cut down the time required for each analysis from 15

minutes to 6 minutes.

36

Discussion of Results

Merit of the Polarographic Method of Analysis

Hydrated copper sulfate at a concentration as low as 0.10
mg in 25 m1 of solution was measured polarographically. During
the evaluation the blank solutions from the test plot were
analyzed and no trace of copper was detected. Spot checks
of the three cells at one time or another with blank solutions
mde up in the laboratory, likewise showed no trace of capper.
It was felt that the polarographic method was consistent, and
that the results obtained from the analyses were reliable.
This was rather gratifying because it was the first time in
the history of the electrostatic dusting project that a de-
Pendable evaluation method provided readily available data

from the actual field tests.

Dust Deposits Analysis

The results of the tests are shown in Table X in the
Appendix B. Figure 13 and Table II show the average values
01" the deposits resulting from different treatments. For
the charged dust, the deposits appear to bear a linear
relationship to the rate of application (curves B and D).
This is not so with the uncharged dust; the increase in‘
dGPOSits between the low and the medium rates was definitely
1988 than the increase in deposits between the medium and

the high rates of dust application. A closer study of the

37

data reveals that for the medium rate of application with
uncharged dust, two out of eight samples collected from the
top leaves had no dust deposits, and for the "hidden"
leaves, four out of eight samples collected had no dust de-
posits. This situation did not exist with the charged dust.
It appeared then that the charged dust gave a more uniform
coverage to plant surfaces than did the uncharged dust. The
variations between deposits for each treatment, at different
duet rates, are shown in Fig. 114. The middle curves repre-
sent the average values of dust deposits on ten square inches
of leaf surface -- counting both sides. The lower curves
I“present the lower; and the upper curve, the upper limits

or the deposits .

comparison of TOp Leaf and Hidden Leaf Deposits

It appeared that, in general, the "hidden" leaves re-
.ce ived slightly more dust than the top leaves. This was not
0396 cted. A closer study of the duster nozzle position
yie lded the following observations: the nozzles had been
aC13'l13ted to project the dust stream straight down, and,
t1’162I2'efore,the blast did not help dust deposition on top
leaVes, but the "hidden" leaves may have received some bene-

ficial effect from the dust reflected from the ground.

1"
J
i

 

38

 

 

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meow sea mondom I Qoapwoaaaaw mo epwm
3 co om 0: on om 2
7l‘ _ _ e _ _ .

 

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mama vewpwnoqd .Geram
mama cowhwno .Qoa

mama powhwsecs .Qoa

«mom

 

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m

°ut or no sqrsodeq qan

eoeyans 3391 Z

TABLE II
AVERAGE VALUES OF DUST DEPOSITS FROM
FIELD TESTS 0N SOYBEAN PLANTS
(Weight in milligrams)

 

 

_
Rate Top Leaves Hidden Leaves
Lbs- per acre Uncharged Charged Uncharged Charged
27.2 0.336 r - 0.u69 0.535 0.u00
h2-3 0.u36 1.251 0.633 1.31h
68.2 1.296 2.14.68 2.141TO 1.983

 

 

 

 

 

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320 500. en:
0

 

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.COprHhm> pamomoo pmdm .JH .mfim

 

 

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Ill

Analysis of Variance

The analysis of variance of the data (Table III) indicates

a significant difference, at the one percent level, between
rates of application. The difference between charged and un-
charged dust is also significant at the one percent level.
There is an interaction between the position of the leaves

and the treatment of the dust which is significant at the

five percent level. The difference in deposits on well-eXposed

leaves and on "hidden" ones is not significant.

Dust Deposition Efficiency

In computing the dust deposition efficiency of the field
tests the following assumptions were made:

1. The total leaf area (both sides) per acre of soybean
plants was estimated to be six acres, on. the basis of Stan-
ley'g work on leaf area (21), and on the maturity of the
Plants at the time of dusting.

2. The average deposits shown in Table II are typical
for the area dusted at the specified rate of dust application.
Furthermore, the deposits for top leaves and for hidden

leaves are added and the average values used in the computa-

tion.

—— 3"... .-

I I.-n‘

‘

I a.“ lir Ill!

h2

TABLE III
ANALXSIS OF VARIANCE 0F DUST DEPOSITS
ON SOYBEAN PLANTS

 

 

 

Source D.F. s.s M.S. F f
g
Total 95 102.5’492 ’ :
Rate 2 A3 .0067 21 .5031; 37 . 9962-:-
{Treatment 1 3.h960 3.h960 6.18ss
Position 1 0.8512 0.8512 1.50
R x T 2 2.0100 1.0050 1.78
R x P 2 0.2387 0.1191; 0.21
T x P 1 2.5221 2.5221 Elm-r.
f2 x.T x P 2 2.8787 l.h39h Z-SM
Etrror 8h h7.5h58 0.5660

 

** - Significant at the 1 percent level
* - Significant at the 5 percent level

 

Sample calculation:
Average dust deposit on ten square inches of leaf area:

0-1L36 mg

Total dust deposit on six acres of leaf area:

6 acres 1 [13,560 ft2 x M in2 x 0.!136 mg 1: lgm x l lb

1 acre 1: 10 in2 x 1 ft2 x 1000 mg x 163.6 gm
3 30617 lbs

 

Efficiency: é612 x 100 = 13.3%

The different efficiencies are summarized in Table IV.
.11: is believed that the values for the uncharged dust, i.e.,
for the conventional dusting practice, are fairly represen-
tative of present-day performance of dueting machines.
However, these values should not be accepted at face value,
tnatz should be taken only as a springboard for more extensive

and intensive studies of duster performance.

TABLE IV
DUST DEPOSITION EFFICIENCY IN
SOYBEAN TESTS

 

 

 

 

Uncharged Dust Charged Dust It
Rate Average Deposit Average Deposit 7
(Lbs on 10 5‘1- in. on 10 sq. in. a
par. of leaf area Efficienc of leaf area Efficienc
acre) (Wt' in mg.) (percent (wt. in "18.) (percent ‘
, ‘ , ;"4
27 . 2 0.14.36 13.3 0.14.714. 134.5
112.3 0.531; 10.5 1.283 25.2

68.2 1.869 22.7 2.225 27.1

 

as

THE EFFECT OF THE IONIZED CURRENT INTENSITIES AND THE
1
EFFECT OF SHIELDING ON DUST DEPOSITION

The effect of current intensities on dust deposition
was first investigated by Hebblethwaite (12). His results ““
were of a qualitative nature, i.e., the dust deposits were
measured in light meter indices and no quantification of the
amount of dust deposited was attempted. The present study . ~a
was made, first to verify Hebblethwaite's results, and second
to evaluate the deposits quantitatively.

At the same time this study was conducted, another
series of tests was run to find out the effect of superimposing
an external electric field on the field induced by the dust
cloud in order to drive the dust to the dust collector and
thereby precipitate it. The external electric field was
generated by impressing a high voltage on a "shield" placed
close to the brass disc. It was thought that the external

electric field, with the same sign as the field induced by

 

the dust cloud, would drive the charged dust particles away

from the shield and on to the dust collector.

___‘

1"Shielding" refers to the use of an external electrical
field force produced by an electric shield.

 

 

 

Experimental Equipment and Procedure

Laboratory Dust Chambers

A brief discussion of the laboratory dust chambers is
given herewith. A more complete description of the dusting
laboratory has been given by Brittain (7).

The test chambers were composed of two compartments, a

dust feed chamber and a dusting chamber.'

The dust feed chamber. The dust feed chamber housed
the dust metering mechanism, the blower, and a set of wet and
dry-bulb thermometers. The blower, from an old hammermill,
replaced the conventional Niagara duster fan in the attempt
to reduce the amount of dust collected on the fan blades.

The blower was driven by a three-horsepower, variable-
speed motor. The motor speed was adjusted to 2500 revolutions
per minute for all tests.

The dust feed chamber was air tight, except for an eight-
inch intake where air was drawn into the chamber by the
sucking action of the blower (Fig. 15). The air intake was
connected to a ducting system equipped with a steam.injector
with which the relative humidity in both test chambers could
be controlled. The duct was arranged so that air could be
taken in from either inside or outside the room.

The wet and dry bulb was of a design similar to the

constant-level wet-bulb system described by Henderson (13).

 

       

A

B
C
D

Fig. 16

Food end of dust feed
mechanism.

A - Cleaning brush
B - Conveyor belt
C - Dust chute

D - Air nozzle

#7

Fig. 15

Dust feed chamber.

Air inlet
Blower
Dust hopper

Conveyor belt

 

h8

The dust feed mechanism. The dust feed.mechanism con-
sisted essentially of a horizontal conveyor belt moving at
a uniform.speed of 0.890 feet per minute (Fig. 16). For each
run, ten grams of dust were distributed evenly lengthwise on
ten inches of the conveyor belt. At the feed and of the belt,
a rotating brush swept the dust into the chute, breaking the
clumps into a uniform cloud of dust. The sheet-metal chute
was placed at a slight angle, inclined toward the inlet of
the blower fan. At the other end of the chute, a small air
stream coming from a compressor operating at nineteen pounds
per square inch was directed parallel to the bottom of the
chute, in order to prevent the dust from depositing on the
chute. This arrangement was found rather effective in pre-
venting the dust from clogging the chute, as mentioned by
Brittain (7).

The dusting chamber. The dust stream coming from the
dust fan was blown into the dusting chamber through a con-
necting tube. The charging nozzle was mounted on the end of
the tube protruding into the dusting chamber. The arrangement
for collecting dust is shown in FigurelJ. The dust collectors
were three-inch discs (Fig. 18) cut from brass shim stock,
0.010 inch thick. The disc was placed h2 inches from the
nozzle, parallel to the dust stream to minimize the effect

of inertial force on dust deposition. An exhaust fan at the

 

 

 

 

   
   
   
  
  
  
  
 
  

A

'11 B] U 0

C)

Fig. 18

Dust collector disc and
electric shield.

Inside

ha

Fig. 17
of dusting chamber.
Protruding nozzle

Wet and dry-bulb
thermometers

Dust collector disc
Shield

Air sampling device
Ground lead to disc

High voltage lead
to shield

 

far end of the dusting box removed the excess dust. The
baffle of this exhaust fan was adjusted so that the pressure
inside the dusting chamber was one-fourth inch of water below
the atmospheric pressure. This slight vacuum was maintained

to keep the dust from leaking into the laboratory.

Charging Nozzle
The charging nozzle used is shown in Fig. 19. This

double—support type was used in preference to the single

support (Fig. 19) type because of its higher break-down

voltage, and higher charging current (Table V). ‘ 14
Fig. 20 shows the inside construction of'a single-support

type charging nozzle.

Electrical Circuit

A tripler circuit provided the high voltage. The maximum
output of this high-voltage power supply was 30 kv and 1 ma.
The input to the tripler circuit wa3213almolt, D.C. power
supply. A rheostat on this power supply controlled the
output of the high-voltage tripler circuit. For each test,
both voltage and current were measured, and the current was
kept constant, as close to the desired value as possible.
The voltage was measured across the charging nozzle with a
Simpson 269 meter, equipped with a special probe (Fig. 21).
An RCA vacuum tube microammeter connected on the ground side

of the charging nozzle indicated the current.

 

51

 

Fig. 19. Two types of charging nozzle.

A - Single-support type
B - Double-support type

 

52

TABLE V
CHARGING NOZZLE PERFORMANCE

 

 

Type Voltage Input to Voltage Output Output Current
Tripler Circuit from Tripler

 

Circuit
(volts) (kilovolts) (microamperes)
Double -— 180 6 . 2 0
Support 200 7.9 2
Nozzle 220 8.6 $3
0 9 . 7
3&0 11.2 163
280 12.8 290
300 .0 MBO
310 .5 A90
320 15.1 530
-..- 15 e 635
Breakdown
8 ingle - 180 6 .5 0
Support 200 7.4 3
Nozzle 220 9.h 17
O 11.3 61
2 0 11.8 135
280 12. 6 265
290 13.0 315
300 13.1 1100

Breakdown

Uzi-.1

 

53

 

Fig. 20. Inside construction of a single-
support type charging nozzle.

A - Main tube of charging
nozzle

B - Plexiglas insulator
C - Charging needle

D - Post to deflect air stream

 

51+

 

Fig. 21. Nozzle charging apparatus.

A - BOO-volt D.C. supply
B - High-voltage probe

C - RCA microammeter

D - Simpson 269 meter

E

- Tripler-circuit power supply

55

Electric Shield

The shield used to superimpose an external electric field
on the field induced by the charged dust cloud is shown in
Figure 18. It was made of quarter-inch hardward screen. A
potential of 20 kv was impressed on the shield during the
desired test. After each test, the residual charge on the

. 0 114-7- E
. 1hr
?
i
F

shield was discharged by connecting it to ground with a high-

voltage probe .

 

g." v v a

The shield was placed parallel to and 3 l/h inches away

from the brass disc.

Operating Conditions

The following conditions were observed for all tests:

1. The relative humidity was held at sixty percent.

2. The air velocity was kept constant; with the blower
speed set-at 2500 revolutions per minute, the air velocity
was 6000 feet per minute at the nozzle, and 800 feet per
minute at the brass disc.

3. Ten grams of dust were evenly distributed by hand
between two fixed marks, ten inches apart, lengthwise on the
conveyor belt.

h. Four dusts were used: standard copper sulfate,
micronized copper sulfate, standard Attaclay, and Atta-
Sorb. For a description and size analysis of these dusts

the reader is referred to Appendix A.

5. The dust density was measured by drawing a known
volume of the dust-laden air through a Millipore filter.
The rate of flow through the filter was 20.11 liters per
minute. Samples were taken for one minute during the un-
charged test and during the lOO-microampere test. The fil-
ters were weighed before and immediately after the sampling,
to avoid possible errors due to moisture exchange with the
surrounding atmosphere.

6. The brass disc was exposed to the dust stream 80

 

seconds during each test. L

EXperimental Design

The following current intensities were used:

0 (uncharged), 10, 20, 50, 75, 100, 150, 200, 300, h00, 500,
and 600 microamperes. Two types of tests were run with these
current intensities. In one type, the shield was not used; in
the other the high potential of 20 kv was impressed on the shield.

A randomized block design with groups and sub-groups was
used. The Shielded and unshielded treatments were designated
as groups to minimize the variations within one current in-
t6neity. Dusts were designated as sub-groups.

Each block was replicated four times. The order of
blocks, groups, and sub-groups was determined randomly by
drawing coded numbers from a box.

During the running of the tests, whenever a sign of
dust contamination from one dust to another was noted, the

tests were rerun after the experiment was completed. It

.1.

turned out that this happened only during the early part of
the experiment when the nozzle had not been cleaned often
enough. If the rerun test included sampling with a Milli-
pore filter, the weight of dust deposited on the filter was
also recorded.

The dust deposit evaluation was made by direct weighing

with an analytical balance.

Experimental Procedure

The experimental procedure was divided into two definite

 

phases, the dusting and the evaluation of dust deposits on
discs and on Millipore filters.

The evaluation phase consisted of weighing and recording
weights of brass discs and of filters before and after dust-
ing.

The dusting phase was composed of the following steps:

1. Starting the motor driving blower,

2. Installing the brass disc,

3. Checking the relative humidity and adjusting it

if necessary,

A. Distributing the dust on the conveyor belt,

5. Installing a Millipore filter when needed,

6. Turning on charging circuit when necessary,

7. Starting cleaning brush at feed end of the conveyor

belt,

58

8. Starting stop watch and conveyor belt simultaneously,

9. Exactly ten seconds later, starting vacuum pump to
draw air through when Millipore filter was used,

10. Turning off pump exactly sixty seconds after it
was started,

11. Ten seconds later, turning off charging circuit, gm
stopping conveyor belt, cleaning brush, and blower,

12. Removing dusted disc and filter for evaluation,

13. Starting motor driving the blower, cleaning the

nozzle,

 

 

‘1!“ t-‘
‘l

18. Discharging the shield if it was used in the test,
15. Beginning again with step number 2.

Between steps 9 and 10, the-appropriate dust was weighed

.for the next test.

Discussion of Results

Millipore Filter Deposits
The results of the Millipore filter deposits are tabu-
ILated in Appendix B, Table XI. Figure 22 shows the average

Ifiilter deposits for the four dusts at three levels of
treatment. Even though the same amount of dust was used,
and the same volume of air was drawn through the Millipore
lillter each time, for each dust, the deposits during the
tulcharged tests are significantly larger than the deposits
cluring both the charged tests and the charged and shielded
ttists. The filter deposits for the charged tests, and the

c"harged and shielded tests, are approximately the same at

59

 

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.mumeQoo hoped“ opedwaauz oweao>< .NN .wfim

 

eQMflHNN

 

 

 

 

 

 

 

 

 

E

 

 

 

 

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aaaoeoo<
oaaeaeem

 

 

 

 

 

 

 

 

 

 

 

 

 

enemasm seduce
essences“:

 

 

 

 

 

 

 

 

 

 

 

 

 

ousmadm noddoo
oawocspm

 

 

moaomsdoaeaa ooa
voodoaam
use someone

eeaoasdoaeds 00H
dowasno

 

 

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ease

 

 

 

 

 

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I‘ll-'1 .e
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each level of treatment. It appears, then, that the charging

of the dust may be responsible for the difference in filter

deposits.

In order to account for the difference in filter deposits,
the author suggests the following explanation. When the dust
is uncharged, the dust cloud distributes itself evenly in

the dusting chamber. When the dust is charged, or charged

"' ’j( ?j

and shielded, the dust cloud has a positive sign. It tends
to accumulate around the collector disc, at ground potential,

and does not disperse itself toward the top of the dusting ; i

 

chamber where the Millipore filter holder is located (Fig. 17).
Thus, the filter deposit becomes smaller, and, at the same
time, the amount of dust precipitated on the collector disc

becomes larger, because of the denser dust cloud surrounding

it.

Effect of Current Intensities
Figure 23 shows the relationship between the charging

currents and the applied voltages. According to the curve,
ionization would occur around seven kilovolts.

The dusts deposited on collector discs are shown in
{Patfles XIII and XIV, in Appendix B. Figures 2k and 25 show
tdie average dust deposits at different levels of charging.

The charging of the four dusts used increased their

iiepositions. For the same amount of dust used, the finely

fl. .l_l..rl .

r. [if ,

 

61

ground dust -- micronized dust -- deposited more heavily than

its coarser counterpart.

The standard Attaclay, the Attasorb, and the micronized
copper sulfate showed a large increase in deposition when
the current intensity was increased from zero to 150 micro-
amperes. Beyond 150 microamperes, increased current inten-
sities did not seem to increase dust depositions appreciably.
The standard copper sulfate, however, showed a large increase
in deposition around 500 microamperes, but its deposition
reached a minimum at 600 microamperes. This sudden decrease
in<ieposition was attributed to the breakdown of the charg-
ing nozzle, although the instruments did not register any
'breakdown during the tests.

The behavior of standard copper sulfate around the

(charging current intensity of 500 microamperes deserves some

further study .

Iiffect of Shielding

For the two standard dusts -- Attaclay and copper sul-
fiate -- shielding seemed to increase dust deposition at
Very low current intensities, 50 microamperes or less. Be-
yxlnd these values, shielding did not seem to affect deposi-

tions of the ’standard dusts.

It is worthwhile to note that the "abnormal" behavior of

the standard copper sulfate persisted with shielding.

 

 

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SQIOAOITY - QBBQIOA

 

 

 

 

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opshasm Rodeos pudendum towasno a m<

 

smeanttrN u: sqrsodoq qan eSeJeav

6h

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moaodEsOAoaz as moauansode Because

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amt - _m a? _ .. _ _ I A I 8.

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smeafirtttw u: sqtsodeq qan eBeJeav

 

O
(x

65

Shielding greatly increased the deposition of the
micronized copper sulfate, but it substantially decreased
the deposition of Attasorb. This decrease was totally un-
expected. It was thought that the shield and the dust
cloud produced by the charged Attasorb were of opposite
signs. If it were true, then the dust, instead of deposit-
ing on the collector disc, would be precipitated onto the -
shield. Careful determination of the dust cloud Sign, with

an.e1ectroscOpe and a known source of positive charge, did

 

riot substantiate the hypothesis and it had to be discarded.

L.

{The cause for the decrease in the deposition of Attasorb
ciue to shielding remains, therefore, unknown.

Table VI shows quantitatively the effects on dust de-
positions due to charging or charging and shielding. The
"charged" values and the "charged and shielded" values are

the averages of deposits at the eleven levels of current

iuatensities used. (See Table XIV, Appendix B.)

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Ho osHm> owmao><

 

 

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me.oau ms.o+ ao.ma+ mm.o+ aoeo oeeoaeaH oez

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H> mum<a

67

SUMMARY AND CONCLUSIONS

The polarographic method of chemical analysis was

applied to the evaluation of pesticidal dusts. Polaro-

graphy was discussed briefly.
A Sargent Model III, manual type, polarograph was used

to measure the concentration of copper in solutions con-

taining hydrated copper sulfate. An electrolyte composed

of 0.h M potassium sulfate and 0.01 percent gelatin, was

found suitable for the evaluation of copper sulfate dust.
COpper concentration as low as 1 ppm was readily

lneasured in standard solutions prepared in the laboratory.

The polarographic method of evaluation was then used

to measure deposits of copper sulfate dust on soybean leaves

after field dusting. Five square inches of soybean leaves

-- ten square inches of leaf area -- were punched into a

The solutions

This

Nash solution containing potassium sulfate.
were analyzed polarographically in the laboratory.

method was found to be satisfactory.

The field tests on soybean plants showed, in general,

“0 (lifference in dust deposits between well-exposed and

hidden leave 3 .
For the three rates of dust application used during

the :field experiment, the efficiency of the duster ranged

 

68

between 13.3 percent and 22.7 percent for the conventional
method of dusting, and between lh.5 percent and 27.1 per-

cent for the electrostatic dusting.

The effect of current intensities on dust deposition

was investigated in the laboratory under controlled con-

ditions.
The laboratory tests indicated that for the micronized

copper sulfate, Attaclay and Attasorb, the dust deposits

increased greatly -- as many as ten times -- with increased

 

current intensities up to 150 microamperes. With further _

increases in the current, the increase in dust deposit was

negligible.

The standard copper sulfate showed a maximum deposition
around 500 microamperes, and a sharp decrease at 600 micro-
ampere s .

Up to about 50 microamperes, shielding improved the
deposition of coarse dusts -- standard copper sulfate and
standard Attaclay -- at low current intensities. Above
50 Inicroamperes, shielding did not seem to affect deposition.

Shielding greatly improved the deposition of the micro-

niZed copper sulfate, but it decreased the deposition of

AtWeasorb.

Illa

 

APPENDIX A
PARTICLE SIZE DETERMINATION

Splinter (20),in.his study on deposition of aerial sus-
pensions of pesticides, and Brittain (7), in his study on the
effect of plant surfaces on pesticidal dust deposition, both
needed the distribution curves and the average size of the
different dusts used during their respective investigations.
The author did the following work to furnish them with the

necessary information used in the quantification of their

results.

Review of Literature

Particle size determination is of considerable impor—

tance in industry. It is also of great concern to chemists,

to public health workers, and to many others. Methods have

been devised by workers in their respective fields. A broad
cI'llssification of these time-tested methods was given by
Schweyer and Work (18) as follows:

I. Sieve analysis

II. Microscopic analysis

A. Conventional microscopic methods
B. Ultramicroscopic methods

 

 

 

II'

_‘ Irv-l:

 

70

III. Sedimentation analysis
A. Increment methods
1. Pipette method
2. Hydrometer method
3. Pressure method
h. Photographic method
B. Cumulative methods
1. Balance method
2. Pressures methods

IV. Centrifugal analysis
A. Ordinary centrifugal methods

B. Supercentrifuge methods
C. Ultracentrifuge methods

V. Elutriation analysis
A. Air elutriators
B. Liquid elutriators

VI. Turbidimetric analysis
A. Gross methods
B. Size distribution methods

VII. Miscellaneous methods
A. Permeability methods
B. Adsorption methods

Crossmon (9) expressed satisfaction in the counting of
dust particles by phase microscopy. Hillier (1h) reported
the use of the electron.microscope in the determination of
the size and shape of particles in the size range from.1)u
to about 5 1191. Jones (15) applied the microprojection tech-
nique to the determination of the size of fine abrasive
POWders, and found it satisfactory for symmetrically shaped
abrasives.

The above-mentioned methods were included in this
writZing for future reference only. It is not the author's
intention to discuss the merits and demerits of each method.

The conventional microscopic method was chosen for the

 

-.T Q A .‘T"..R.§
i»

.1-

 

116..

7b
.1

fit

“In.

 

71

determination of dust sizes. This method was selected on the

basis of reasonable accuracy, coupled with speed of operation.

It also yields the size—distribution curve directly.

Equipment and Technique
A Bausch and Lomb laboratory microscope with a 10x
eyepiece and a u3x objective, with numerical aperture 0.85

was used. A lOO-watt spherical illuminator was the source ;

 

of illumination.

317—...»

Sampling

The dust contained in a bag was thoroughly mixed. A

cotton-tipped applicator was then dipped, with a rotary

Inotion, into the sample. A small portion of the dust ad-

hered to the applicator. It was transferred to a clean

znicroscopic glass slide by gently painting the glass surface

‘with.the applicator. A light blowing on the slide dispersed

the dust clumps and a thin layer of dust was left on the

glass slide ready for microscopic determination.

COtunting

A.magnification of h30x was used. Light-field illumi-

nairion was selected because it was felt that submicroscopic
Particles ((0.5 )1) are relatively unimportant in dust

dSENDSition, and because the percentage by weight of these

 

 

".
. -ih...

‘

 

72

su‘mnicroscopic particles would be negligible in the final
analysis.

The linear measurement (Fig. 26) of the dust particles
under the microscOpe was accomplished by a direct compari-
son with a scale incorporated in the ocular of the micro-
scope. This scale was first calibrated against a stage 1”“
micrometer.

Ten fields (Fig. 27) were picked on each slide, and

four slides were prepared from each dust, totaling a count

 

of forty fields for each dust studied. 3 . i
The fields for counting were picked at random by

moving the slides under the microscope. To count very

small particles (\(lp), the slide was moved slightly side-

ways; the particles were then seen moving and more easily

detected. They showed up as gray specks and were not as well

defined as particles above 1):.

Results

Particle size determinations were made for the follow-

ing dustsl:

l. Micronized talc (sack l)

\

(1 1Because of an error in labeling the various sacks of
u.st when Splinter and the author were working together, some
°f the dusts coming from different bags were analyzed twice.
e author then went ahead and presented the data as if all
e dusts were different from one another. He left to the
discretion of Splinter the decision to lump the data from
he same dusts together for final analysis.

73-

 

 

 

g\s( r— {_ ~s"
~. . . . .

A

{,3 5‘

\f-
”r
.a.

.'
-1136

7'

 

 

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Hllilll

 

L.

'3“
'l ‘)

3‘“

.1...

l

A .

“was: --
U-.

.-‘U

:1 line

\

fiDtL‘

«a.

711

2. Micronized Attaclay (sack l)
3. Red-dyed talc ' ‘
u. Standard Attaclay

5. Micronized clay (Attasorb)
6. Standard talc '
7. Micronized talc (sack 2) r‘“w“
8. Micronized Attaclay (sack 2)

9. Micronized copper sulfate (Cu SO“ , 5H20)
10. Standard copper sulfate (Cu 80“, 5H20) A

 

The results were tabulated in Table VIII and the size- -J
frequency curves plotted from Table VI are shown in Figures
28, 29, and 30.

The standard talc and Attaclay (Fullerh earth) dusts
were 25-mesh dusts used as commercial fillers. The standard
c>0pper sulfate was a commercially available dust under the
name "powdered bluestone." The micronized talc, Attaclay,
arua copper sulfate were obtained by running the regular
dhxsts through a micronizer. This operation was described by
Blfiittain (7, page 32). The red talc was micronized talc
Wtuich.had been mixed with a water-soluble red organic dye,
Linked Scarlet (6), and then reground. The Attasorb was a

commercially available finely ground clay.

AVerage Diameters
The median diameter of each dust was determined from the

Size-frequency curves. According to Green's definition (11).

75

an average diameter is the diameter of a hypothetical
particle which in some ways represents the total number of
particles in a sample. A full description of the size of

a non-uniform particulate substance requires the determina-
tion of several average diameters (10). Drinker and Hatch
(10, page 1147) listed the mathematical definitions of the
several average diameters necessary for a complete definition
of size. Only the average diameter from the arithmetic mean
was presented in this result, because it was felt that this

value was adequate (Table VII).

 

76

acosoaz no omen

 

 

 

oq an on mm on mH 0H m o
a! _ _ _ a a _ _ .1
_ .m ..
: a
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mm .mam \\\\
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b . \ \
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71- - - - puhlu-.|..|- .a ooH

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Kauanboad quay deg oaxqunumo

 

77

scopes: as anew

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W m _ _ 1 _ a 4

ON

u---]-—--—-—o——o—-

 

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am .wam

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78

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m>mbo NoZMDOHmL u WNHW

Kouenbead queo Jed anxqetnmno

79

TABLE VII
CUMULATIVE SIZE-FREQUENCY DISTRIBUTION

Dust gameter in micrcms
0-5 1.5 3.0 5.0 7.0 9.0 11.0 16.0 25.0 35.0

 

Micronized talc 26.0 52.3 71.5 82.9 89.8 93.1 95.8 99.6 100.0
(sack l)
mcronizOd AttfiClay 1‘50")» 8702 9509 980,-.- 9901 9907 10000 i:
(Back 1)
E. J

 

Standard Attaclfiy (+0.1 73.9 85.8 9106 9’40”. 9698 9603 9909 10000

Micronized clay (+3.3 85.8 9506 9803 9903 9908 9909 10000

(Attasorb)
Standard talc 17.3 111.14. 611.3 711.9 82.1 87.8 91.3 97.6 99.1 100.0
MicI‘<>n:l.zed talc 17.8 87.5 68.0 79.8 86.6 91.2 914-5 99.5 100-0
Back 2)
Micronized Attaclay 53.5 87.9 96.2 98.6 99.2 99.6 99.9 MILO
(sack 2)
Micronized copper- 20.0 75.7 95.14 98.7 99.6 99.9 100.0
sulfate

Standard copper- 10.0 8.2.3 61.8 72.0 77.11 82.8 86.1 96.3 99.1 100.0
Sulfate

 

‘

AVERAGE DIAMETERS AND DENSITIES OF DUSTS

TABLE VIII

80

 

 

Dust

_ Avergge Diameter
Arithmetic
Mean

(microns) (microns) (gm/cm3)

Medianj

Particle
Density

Reference

 

Micronized talc
(sack 1)

M1 cronized Attaclay
(sack 1)

Red-dyed talc
Standard Attaclay

Iiicronized clay
(Attasorb)

Standard talc

Idicronized talc
(sack 2)

Micronized A ttaclay
(sack 2)

Idicronized copper-
sulfate

Standard c0pper-
sulfate

3.uh
1.37

2.63
2.21
1.hl

11.711
3.93

1.28

1.79

5.50

l.h0

0.50

1.10
0.80
0.80

2.00
1.70

0.50

1.00

2.00

2.8

2.85

Z-hS
2.85

2.8
2.8

2oh5

(22)

(1)

‘E a

 

(1)
(1)

(22)
(22)

(1)

1From size-frequency curves, Fig. 28, 29, and 30.

 

TABLE IX
PARTICLE SIZE DATA

81

 

 

 

 

Dust Rep. Diameter in Microns
(1; 1-2 2-1 11-6 6-8 8-10 10-12 12-20 20-30 >,30
Micronized 1 75 83 77 36 22 6 7 12 1
talc 2 68 80 61 37 111 9 7 11 1
(sack 1) 3 S7 51 29 28 19 11 9 7
h. 70 58 33 17 16 5 5 16 2
Micronized 1 1%6 11111 111 13 6 3
Attacla 2 2 6 223 111 15 l 2
(sack l 3 172 1110 28 8 2 3 3
. 11 209 223 14.2 7 La. 1 2
Red-dyed 1 132 96 119 37 18 18 6 13 2
tale 2 )30 69 11% 21 8 9 5 6
3 8 1115 7 116 17 10 LI- 1
)1 1118 117 29 20 l)... 1 l1 2
Standard 1 116 73 3 21‘ 8 8 3 L1 1
Attaclay 2 75 78 1 10 8 6 6 3
3 92 88 37 9 S u 2 6
ll» 92 77 21+ 15 5 1+ 3 2
Micronized 1 139 114.3 30 12 )1 l
clay 2 129 1116 32 7 5 1 1
(A ttasorb) 3 179 171 39 9 2 3
, L1 180 156 L10 11 3 2 1
Standard ' l 21 59 53 26 18 15 6 111 2 1
‘ tale 2 36 57 55 19 111 9 9 9 1 l
3 38 3O 27 22 10 11 8 111 5 3
11 113 116 117 18 15 10 5 13 LL 2
M1 croni zed 1 35 611 L16 29 17 11 8 11 1
tale 2 111.1 72 36 17 16 10 6 1% l
(sack 2) 3 1+3 67 59 33 12 10 5 1
u 81 70 87 29 18 ll 11 15 2
Imicronized 1 182 137 38 6 )1 1 l
Attacla 2 192 132 33 8 LL 1
(sack 2 3 215 1115 35 13 1 l1 2 l
. 11 209 97 17 9 1 l
micronized 1 12 126 51 9 2
COpper 2 I111 90 18 5 1
Eulfate 3 112 112 29 7 2
u 31 115 39 S 2 2 1
Standard 1 9 112 211 11 7 5 6 11 2
cupper 2 5 £12 20 12 )1 6 L1 13 3 l
Sulfate 3 3o 20 111 7 9 3 11 2 1
L1 1 35 26 10 7 5 2 12 6 2

APPENDIX B

EXPERIMENTAL RESULTS

82

 

 

 

 

 

 

TABLE X

83

DATA OF FIELD TESTS OF SOYEEANS DUSTED WITH
STANDARD COPPER SULFATE

(Weight in milligrams)

 

 

 

 

 

Iiate Top Leaves Hidden Leaves
Uncharged Charged Uncharged Charged

L0" 0010 0069 0010 0090
0.20 1.19 0.82 0.88

27.2 lee 0059 00,41 0096 0.36
per acre 0.12 0.83 0.59 0.59
0.69 0. 0.68 0.83

0.36 0.2 0.56 0.23

0.27 0.32 0.60 0.32

0.36 0.21 0.37 0.56

0.82 2.27 l. 7 1.11

112.3 lbs. 0.39 2.01 0.85 1.69
per acre 1.85 1.69 0.90 1.92
0.83 0.20 0 0.72

0.81 1.66 0 2.70
0 0.20 0 0.71
0 0.90 0 0.72

1.68 1.30 1.73 1.56

6802 lbs. 0.59 2038 1089 1065
per acre 0.86 2.77 1.93 2.23
2.16 1.60 5.00 2.65

3.20 1.80 3.80 0.81

0.63 2.58 0.65 1.26
0.52 3.00 2.36 1.71

.‘ Alli”
ll
\

 

TABLE XI

MILLIPORE FILTER DEPOSITS
(Weight in milligrams)

A

‘v

Standard Micronized Standard

88

 

Dust Cepper Sulfate Copper Sulfate Attaclay Attasorb
UnCharged 2.6 7.0 Be; 706 7.3 1105 13.0 1809
.5 8.0 9.2 8.3 1 .9 8.7 11.9 13.8
Average 6.53 8.80 9.72 18.30
deposit .
Charged 308 507 500 303 (400 208 6.6 Sol
(100 micro- 2.9 2.6 ‘ 3.2 2.9 3.8 2.5 5.7 3.6
amperes) 3.1 2.0
Average 3.75 3.60 2097 5.25
deposit
Charged and 2.8 2.9 8.2 3.6 8.1 2.7 6.2 6.7
Shielded 3.3 2.0 Be; 209 8.8 208 7014. 5.8
(100 micro- 2.6 2.0
amperes)
Average 2.65 3.55 3.17 6.53
deposit

82.82 8.8«« .«.82 8.82 8.82 8.82 8.82 8.82 8.8 8.82 8.82 8.8

8.2 8.8 8.2 2.2 «.2 8.2 0.2 «.2 «.2 2.2 «.2 2.2 82
8.8 8.8 8.8
88.8 3.88« 8.02 8.8 8.8 8.8 8.82 8.82 8.8 8.8 8.8 8.8 8.8 8.8

8.8 8.8 8.8 8.8 8.8 8.8 8.8 8.8 8.8 8.8 8.8 8.8 m»

m.0 m.0 m.0 3.0 3.0 3.0 m.0 3.0 4.0 3.0 :.0 8.0
83.0 m.o:m 8.0 m.0 4.0 :.0 :.0 m.0 m.0 m.0 3.0 3.0 3.0 3.0

 

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8.82 8.82 8.82 8.82 8.82 8.82 8.82 8.82 8.82 18.82 0.82

08.82 0.«88 8.82 8.82 8.82 8.82 8.82 8.82 8.82 8.82 8.82 8.82 8.82 8.82
8.82 8.82 8.82 8.82 8.82 8.82 8.82 8.82 8.82 8.82 8.82 8.82 008

8.82 8.82 8.82 8.22 0.82 8.82

«8.82 8.828 0.82 8.22 8.82 8.82 2.82 8.22 0.82 8.82 8.22 8.82 8.82 8.82
8.82 8.82 8.82 «.82 8.82 8.82 8.82 8.82 8.82 8.22 8.82 8.82 008

8.82 8.82 8.82 8.82 8.82

88.82 8.888 8.82 8.82 8.82 8.82 8.82 :.«2 8.82 «.02 8.82 8.82 8.82 8.02

.. - .. - .. 8.2.8 8.22. .82....82 8.22 2.2.92. 8.2.2 2.22-2.8. 8.22 - - -22 ..

8.82 8.«2 0.82 «.82 2.«2 8.«2 8.«2 8.«2 8.«2 8.«2 8.«2 8.«2

88.«2 2.«8: 8.«2 8.«2 8.«2 8.«2 8.82 0.82 8.«2 8.«2 8.«2 8.«2 8.«2 8.82
0.82 8.«2 8.«2 8.«2 8.«2 8.«2 8.«2 8.«2 8.«2 2.«2 8.«2 8.82 008

8.22 8.22 8.22 8.22 8.22 8.«2

08.22 8.888 8.22 8.22 8.22 8.22 8.22 8.22 8.22 8.22 8.22 8.22 8.22 8.22
8.22 8.22 8.22 8.22 8.22 8.22 8.22 8.22 0.22 0.22 8.22 8.22 00«

8.02 8.02 8.02 8.02 8.02 0.22

28.02 8.8«8 8.02 8.02 8.02 0.22 0.22 8.02 8.02 8.02 «.22 0.22 8.02 8.02
8.02 8.02 8.02 8.02 0.22 8.02 0.22 8.02 8.02 0.22 8.02 8.02 082

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2 .8003 222 8282.2

L

and
Shielded

Attasorb

Charged and Charged Charged and Charged Charged

Shielded

Shielded
2.2 1.7 2.5 1.5 2.3 3.0 2.0 2.0

5.7 7.9

TABLE XIII
RESULTS OF TESTS ON THE EFFECT OF CURRENT INTENSITIES
(Weight in milligrams)
Charged
11.0 3 . 6

AND SHIELDING ON DUST DEPOSITS

Shielded

Charged Charged and

Standard Copper Sulfate Micronized Cgpper §_u_1fate gtandard Attaclay
105 202 39“ 108

 

or
Uncharged

 

 

 

Current in
Microamperes

O

25.1 32.3
30.1 30.

9.2 19.7
1h.7 16.1

IAN

uxwx
«:8-

84»
do
04:1"

1AM

10

20

902 12.9 1103

.2 15.0 1
.0 3.6 15.11127 11.11

.16
.95

-#:1

50

L. 21.1 11.8 11.1.
1 22.8 13.0 12.1;

7
3
.9 114.0 25.5 11.9 16.14.

.1 15.7 20.0 10.9 12.2

1
2

75

%

3.8
11.9

100
150

200

_ - ‘ l‘A‘
.

 

TABLE XIII (Cont.)

 

 

Current in

Attasorb

Standard Attaclay
Charged Charged and Charged Charged

pper Sulfate Micronized Copper Sulfate
Charged

Standard Co

31—-

Charged and

Charged Charged and

 

Microampere

and
Shielded

Shielded

Shielded

Shielded

 

300

uOO

ON

11.0 21.0 1
13.6 27.0 1

500

600

 

89

 

 

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82.«2 02.2« 0«.8 «8.8 02. 8 88.8« 08.8 8 .8 0002
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88.w 88.fi 82.8 «8.8 0N.8« «8.82 88.8 «0.8 02 0002
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91

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