Title: Emission spectrochemical determination of residual trace elements in sponge copper powders
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Title: Emission spectrochemical determination of residual trace elements in sponge copper powders
Physical Description: vi, 68, 1 l. : illus. ; 28 cm.
Language: English
Creator: Yoakum, Anna Margaret, 1933-
Publication Date: 1960
Copyright Date: 1960
 Subjects
Subject: Spectrum analysis   ( lcsh )
Copper -- Analysis   ( lcsh )
Chemistry thesis Ph. D
Dissertations, Academic -- Chemistry -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
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Thesis: Thesis - University of Florida.
Bibliography: Bibliography: l. 62-67.
Additional Physical Form: Also available on World Wide Web
General Note: Manuscript copy.
General Note: Vita.
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Bibliographic ID: UF00097997
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000423877
oclc - 11022061
notis - ACH2282

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EMISSION SPECTROCHEMICAL

DETERMINATION OF RESIDUAL TRACE

ELEMENTS IN SPONGE COPPER POWDERS










By
*--JNA MARGARET YOAKUM











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\ % -i- .' I-' '.'













ACKNOWLEDGMENTS


The writer wishes to express her grateful appreciation to

everyone who has assisted her with this research and dissertation.

Special thanks are due to Dr. A. H. Gropp, her research director,

for his excellent supervision and advice. Many valuable suggestions

were provided by all the members of the writer's supervisory com-

mittee, and especially by Dr. J. D. Winefordner. The writer is

deeply grateful to her parents for their interest and encouragement

which greatly facilitated the completion of her graduate work.

The research for this dissertation was made possible through

the cooperation of Greenback Industries, Inc. The writer especially

wishes to thank Mr. H. R. Forton, Vice President of Greenback

Industries, Inc., for his ever readiness to procure all needed equip-

ment and his unfailing friendly cooperation.













TABLE OF CONTENTS


ACKNOWLEDGMENTS

LIST OF TABLES

LIST OF FIGURES

Section

I. INTRODUCTION

II. HISTORICAL

A. Emissaon Spectroa nemical Analysis of Trace
impurities in Copper

B. Emission Specirochemical Powder Techniques

III. BASIC PRINCIPLES

A. Theoretical Considerauona

B. Internal Siandardia lLon

C. Determination ol Arc Temperature

D. Inherent Advantages of a Copper Matrix

E. Standard Addition Method of Analysis

IV. EXPERIMENTAL APPLICATIONS

A. apparatus and Reagenlt

B. Experimental ObservatLons

C. Procedure


Page

ii

v

vi









TABLE OF CONTENTS (Continued)


Page

IV. EXPERIMENTAL APPLICATIONS (Continued)

D. Experimental Results 43

E. Discussion of Results 58

V. SUMMARY 61

BIBLIOGRAPHY 62

BIOGRAPHICAL ITEMS 68













LIST OF TABLES


Table Page

I. Ionization Potentials and Liquid Ranges 22

II. Source Conditions 27

III. Spectrographic Conditions 28

IV. Deelop;ng Conditions 29

V Reagents Used to Prepare Eulk Solutionas i

VI. Analytical Line Pairs and Their Characterisiics ;5

VII Operating Conditions 40

V[[I. Chromum Additlon Series 45

IX. Iron Addition Serej 45

X Lead Addition Ser.es 4b

XI. Mllang3nese .ddiion jeres 4u

XII Nickel Addition Sere3 47

XII. Silver ndditlon Series 47

XIV. i.nc Addition 'Series 48

XV. .%nalys.s oi Matrix Copper Solution 48

XVI True Concentrations of the Fifty-Four Synthetic
Solution Standards 50

XVII. Analysts of Production Batches i3., 1912 and 2145 54

XV111. ,nalys.s of Producton Batch 204 58













LIST OF FIGURES


gure Page


1. United Carbon ultra-purity preformed graphite
electrodes 31

2. Plot showing the distribution of the intensity
ratio Fe 3025. 84/Cu 3024.99 about the mean 36

3. Volatilization curves for zinc, lead, iron,
manganese and chromium 38

4. Volatilization curves for silver, nickel and tin 39

5. Extrapolation to the residual chromium concentra-
tion in the master copper matrix solution 49

6. Solution working curves for nickel, manganese
and chromium 51

7. Solution working curve for silver 52

8. Solution working curves for tin, lead, iron, and
zinc 53

9. Powder working curves for iron and nickel 55

10. Powder working curves for tin, lead and zinc 56

11. Powder working curves for chromium and man-
ganese 57













I. INTRODUCTION


The problem of the determination of trace quantities of im-

purities in metals has existed almost since the time of the first metal

preparations by the cave men. In recent years it ha- become more

and more apparent that important scientific advances have been

attained because analytical methods have been developed for deter-

mining very low concentration; of certain elements. Today entire

industries are greatly influenced because of the ability to determine

or control trace amounts of elements present in materials. Emission

spectroscopy is one of the few methods available for analyi'cal work

at trace levels

All anilyrcal methods have in common the problem of standards

.Much work has been done by the Nstional 3Bureau of Standards ,*itn

the cooperation of other Intereated laboratories on methods for

findiJg ani solving the problem of accurate, certified standards for

direct metal analyzes At present certified standards are available

for nnimerou.s alloys, covering the najor conitiutients of the alloy

and including many minor components. However, the situaUon for

the trace level contaminants is not so ca&SiL soa.ed At trace

concentration levels it ie n3t unreasonable to assume that segregation








problems are likely to be of even greater magnitude than in the case

of minor components and therefore a quick solution of the standard

problem is not likely.

One of the major limitations of quantitative emission spec-

troscopy is the necessity of having available standard samples with

physical and chemical properties similar to those of the unknown.

Recourse to chemical methods in the analysis of trace level impurities

does offer a means for providing standards for the analytical problem

at hand. It is readily recognized than in an analytical procedure

where one step insures a complete solution a common denominator is

established. Starting at this point, additions of known amounts of

impurity may be made to the sample solution and the necessary

standards thus obtained.

The purpose of this research was to develop a rapid, accurate

method requiring a minimum amount of sample preparation for the

determination of the residual trace impurities in sponge copper powders.

Solution standards were prepared and the powders were analyzed by a

solution technique. A direct powder technique was then developed

which was rapid enough to be useful in production control and which

gave an accuracy comparable to the solution method. The sensitivity

of the powder method was found to be much greater than that of the

solution method.













UI. HISTORICAL


A. Emission Spectrochemrical Anaiys.a of Trace mrpuriteea in Copper


rour general methods have been used in the determination of trace

impurities in copper. The earliest work was done by Breckpot (1-4)

..nd hia co-workers who employed a quantitative method based on the

use of cupric oxide ponders The samples were dissolved in nitric

acld and alter appropriate treatment they were converted to cupric

ox:ie and the oxides of the impurities. This ponder waa placed in

the cavity of the lower carbon electrode and aniiy.ed using direct

current arc excitation. Thirteen elements, bismuth, arsenic,

antimony. tin, lead, cadmium., ,Lne, aluminum. barium, calcium,

magnesium, germairunm and gold were determined in electrolytic

copper.

Solution methods hive alio been used in the analysis of copper

for impurities. Park (5) and Lewis (6) proposed an indirect solution

method in which they analyzed the residue from 0. I ml. of solution

dried on graphite ufsng direct current arc excitation. An Intermittent

arc was used by Ratsbaum (7) in the determination of lead in copper

solutions. A modification of this method Mas introduced by Jaycox

and Puehle (8) which utiL-zed a mecha usm to rotate the sample

electrode at 600 r. p. m.








One highly successful technique for the determination of im-

purities in copper samples is that of the globule-are method (9-11).

The specimen melts to form a globule during the analysis. It has

been found that considerably greater sensitivity is obtained in this

way than if solid electrodes are used. The electrode cup should

be just sufficiently deep to keep the globule in place. A copper rod

is used as the anode in place of graphite. This technique, employing

a 7-amp. arc, is the method recommended by the British Non-ferrous

Metals Research Association for the determination of impurities in

copper.

The fourth general method for the analysis of trace impurities

in copper employs the solid sample as the cathode for the analysis.

The samples are prepared in the form of rods usually 3 mm. in

diameter (12). The anode is a graphite rod. An interrupted arc (13),

an alternating current arc (14) as well as the conventional direct

current arc have all been utilized as the source of excitation in this

method. Schatz (15) his modified this method until it has a sensitivity

capable of detecting lead, tin, iron, nickel, silicon, bismuth and

aluminum at levels of 0. 001%. This method differs from the conven-

tional arc analysis in that it is based on the excitation in a selected

region in the vicinity of the cathode using a triggered discharge which

is heavily over-damped.








B. Emission Spectrocherracal Powder Techniques


There have been two general methods of handling powders for

emission spectrochemical analysis. One, used prmnrily for the

determination of trace impuritie handles the powdered sample

itself, while the other, used for samples of widely varying major

constituents, utilizes the addition of suitable materials to the sample.

Numerous methods and appitcatlons have been developed wherein

substantial portions of other materials have been combined with samples

before spectrochernical analysis which produces desirable spectrogaphic

cffecti. These materials may be classified as dispersil agents,

dilution agents and co-distjiltic.n agents. Since a single addition

material may alter the arc in several ways, it is usually not possible

to classify any given addition material as belonging exclusiJely to

one particular type. Lithulm carbonate, for example, is added for

the purpose of lowering the arc temperature. However this causes an

enhancemeor of lines of lov eo.cilation potential.

Any material which does noT readily melt at arc temperatures

or hluch has a low surface tension in the fused state will be adapt-

able as a dispersal agent. The most frequently used dispersal agent

ia graphite (16) actually m:.ny benefits other than simple dis-

persion are derived from the addition of graphite to powder samples.

A non-metallic sample may be rendered electrically conductive by

blending It with an appropriate amount of graphite (17, i8). In 1935,









Preuss (19) showed that the addition of carbon powder to powdered

silicate minerals greatly increases the burning qualities of a carbon

arc and supresses fractional distillation. Carbon is also an im-

portant fluxing agent since it is active in reducing materials such

as oxides to metals (20).

Dilution agents are widely used in emission spectrochemical

procedures. One or more of the following effects may be obtained

by dilution: introduction of a new internal standard material,

reduction of self-absorption, creation of a more nearly constant

excitation level in the discharge with samples of varying composition,

and at times, the determination of the percentage of the major con-

stituents of a sample. The quantitative analysis of 0. 1 to 1. 0 mg. of

powdered sample is possible without prohibitively small weighing

when the sample is mixed with a large excess of a dilution agent (21).

Most of the accurate methods of emission spectrochemical analysis

employ internal standardization. In many instances the internal

standard is added to the specimen in a constant amount. Where maxi-

mum sensitivity is desired with a minimum of dilution of the sample,

only small amounts are added (22, 23). The addition of large amounts

may provide a dual function of diluent, or flux, and internal stan-

dard (24, 25).

The term spectroscopic buffer is sometimes used loosely and may

indicate any compound added in excess. In the stricter sense, it








is concerned only with buffering of the temperature of the excitation

within the source. A change in the composition of the specimen will

alter the composition of the arc gas and hence its effective ion-

ization potential. When a mixture of elements enters the arc column,

the element of lowest ionization potennrl is the most important in

controlling the arc temperrtucr. In order to buffer successfully

against temperature fluctuations in the arc source, a significant

amount of an element of low ionization potential mu be added to

each specimen. Lithium carbonate has often been auccesaiully used

as a temperature buffer (26.-32).

The control of volatilization is no: a direct consequence of

temperature control. It is intimately concerned with flu'dng. de-

composing and subsequently reducing the sample to metals, the

atoms of wrich murt actually be berated from the sample and reach

the arc gas for emission of atomic spectral ines. The main ad-

vintage of adding an excess of some material is to reduce the samples

to a predominately common matrix for the purpose oi ctabiliaing and

standardizing sample excitanon. Marks and Potter (33) have found

that in some instances the Intensity ratios are very sensitive to

matrix variations. By employing a common matrix it has been possible

to overcome the influence of compositional changes in the sample

itself on line intensity. The reduction of the densities of the principal

Lnes of the major components and the elimination of self-absorption







at high concentrations are accomplished by the addition of a common

matrix material (34). Jaycox (35- 8) and others (39,40) have described

the quantitative and semi-quantitative determinations of a number of

elements in a wide variety of materials by use of a copper oxide

matrix. The use of copper metal powder as a carrier on which trace

metal contaminants of petroleum fractions are deposited is reported

by Hansen and Hodgkins (41). To date most of the semi-quantitative

methods employ powdered samples with an added material which

serves as a common matrix (42-46).

Fluxes are distinguished from diluents on the basis of their

reactivity with the sample to produce a new form of constituents in

the sample. Carbonates and known mineralizers such as sodium

tungstate (47) are practical fluxing agents. Marks and Potter (48)

employed barium carbonate effectively as a fluxing agent.

Co-distillation agents are primarily materials that appear in the

same portion of the arcing cycle as the elements to be analyzed. The

best-known method involving a co-distillation agent is that of carrier

distillation (49, 50).

Carrier distillation is a technique in which the phenomenon of

fractional distillation is turned to good advantage. It is sometimes

desirable to suppress emission from an element which is likely to emit

not only an extremely complex spectrum but also an intense general

background due to continuous radiation. Background and a very intense








spectrc:m lower sensitivity and cause interference. A- small

quantity of a substance of intermediate boiling point is added to the

powdered sample to facilitate the distillation of the volatile impurities.

The carrier provides a controlled removal of impurities from the re-

fractory base. At the same time the carrier moderates the character

of the arc discharge. The smooth and steady nature of the excitation

caused by the controlled volatization of the carrier substance ia also

of gr-3at value

scribner and M.lun (51) describe a method of analyzris for

vnr;ous elements in uranium o:de which is applicable to refractory

o'j-dea and minerals. Uranitam i very involatiie and 2. C,'o gaiLium

o ide is added to suppre-: its volaLli.,ation but not that of the more

volJile elements present. If th. exposure is terminated before the

main volatilizatior of uranium begins, Lhe spectra of lth more

volatile elements can be examined in a relatively clean spectrum.

Ereckpot (52) used a method similar to the above, but he employed

indium o:ude and silver chloride In place of gallium odde.

A technique has been described by Paterson and Grimes (531

which permits the determination of boron and silicon in poNdered

samples through their controlled evolution with fluorine. Cupric

fluoride decomposes when heated by relatively low amperage arcs to

provide labile fluorine which will combine with boron ,nd silicon to

form volatile fluorides. These fluorides can be distilled preferen-

tially from a deep cratered supporting electrode.








Many workers have directed their attention to the problem of

direct handling of the powder for emission spectrochemical analysis.

One of the more popular methods involves the packing of the powder

sample into the crater of the lower graphite electrode (54-57).

Various sources of excitation have been used with this method (58-61).

A general improvement in the stability of the arc was noted by

Stallwood (62) when air cooled electrodes were used for the emission

spectrochemical analysis of powders.

An apparatus for exciting, with a condensed spark discharge,

the spectra of solid substances in powder form has been described by

Berton (63). The lower of a pair of vertically mounted graphite

electrodes is a cup placed between an auxiliary pair of horizontal

graphite electrodes whose function is to heat the cup containing the

specimen. With this scheme it is possible to obtain the lines of most

volatile elements such as mercury, bismuth, cadmium and lead with-

out interference from the many lines of the more refractory elements.

Ethyl alcohol (64), glycerol (65, 66) and water (67) have been

added to powder samples to form a homogeneous suspension which is

applied to the graphite electrode. As the suspending agent is driven

off by heating, it leaves the electrode uniformly coated with the

powder. Ratsbaum (68) has mixed the sample with dextrin glue to

prevent loss when the arc is struck. Another method of applying the

sample to the electrode is described by Bergenfelt (69). A graphite








rod with a longitudinal depression filled with glue is rolled in the

powdered sample.

A new method, which gives very high precision, has been described

by Danieleson, Lundgren and Sundkvist (70). The powdered material

is distributed in an even layer on an adhesive tape which passes through

the spark gap at such a speed that every single spark always hits

new material. In this way the deviations in intensities obtained from

the single sparks during the sparking time are randomly distributed

and are not systematically influenced by volatility and electrode tem-

perature so thai all the sparks belong to the same statistical distri-

bution.

In an attempt to overcome the dificulties of selective vapor-

ization and arc temperature fluctuation, several workers (71-76)

have employed a method in which the powder sample 1s allowed to

fall from above into the discharge zone between two electrodes. The

main advantage of th a method is better reproducibility of results. A

novel procedure for the introduction of the sample into the arc column

is described by Sergeev (77) in which a magnetic field In utilized to

draw the material into the arc.












III. BASIC PRINCIPLES


A. Theoretical Considerations


Emission spectrochemical analysis of materials is based upon

the fact that each chemical element in the vapor state, under suit-

able thermal or electrical excitation, emits radiation composed of

characteristic wave lengths, or spectral lines. The basis of

qualitative analysis is that the wave lengths of the spectral lines

emitted by each element are different from those emitted by any

other element. Quantitative analysis is based upon the fact that the

intensities of the spectral lines emitted by each element under

controlled conditions of excitation and constant sample matrix

conditions are proportional to the concentration of that element in

the specimen.

The intensity of a spectral line emitted from an assemblage of

radiating systems depends upon the number of emitters present in the

assembly that are in the initial energy state, Ei, concerned in the

transition giving rise to the line and to the probability of the tran-

sition. This intensity is defined as the amount of energy per second

radiated by the source at the frequency of the line in question and

caused by transitions between energy states of the atoms in the source.








A certain portion of this energy will pass through the slit of the

spectrograph and fall at a particular position on the photographic

plate and there produce the latent slit image which permits the re-

cording of the line by the photographic plate. The well-developed

techniques of spectral photometry enable one to determine the relative

intensities of the spectral lines in the source from measurements on

the slit images recorded on the photographic plate.

The absolute intensity of a spectral line radiated by an

assembl-ge of itoms is given by

I A..N h (1)
m aJ m
%here

Im = the energy radiated per unit time per uzit solid

angle in a given direction:

Ai = probib lily of Lae transition from energy state E

to energy state E

N = the number of excited jtrms (Lons) in an atomic gas

in atoms per cubic centimeter.

h P Planck's constant, 6.6 x 1027 erg- ec.

S = frequency of the spectral line emitted.

It has been ahcwn (78) that Lhermal equilibrium ipproximately

exats in the flame source and the direct current are source. It is

rather doubtful th.t thermal equilibrium exists in a high voltage spark.

However, the distribution of atoms, ions and moiccu'leo in a spark







should be reproducible if source excitation conditions are maintained

constant. The source is a very critical component in the analytical

process. It is the stage in the entire analytical operation that deter-

mines the sensitivity and the reproducibility of a method.

For the experimental work described in this dissertation, it was

found that Uni-arc conditions gave the most reproducible results. The

sensitivity characteristic of arc excitation and the reproducibility

resulting from spark excitation are both available when the Uni-arc

is used as the source of excitation. It is a uni-directional arc which

is in operation only on the positive half-cycle of the alternating

current flow. A high voltage spark of about 12, 000 volts is super-

imposed on the arc during the positive half-cycle as well as through

the negative half-cycle. Because arc conditions were used it can be

assumed that thermal equilibrium existed in the arc discharge. Later

in this section this statement will be qualified to account for any

deviation from thermal equilibrium. The distribution of atoms in

the spark type discharge will also be considered at that time. Since

thermal equilibrium is assumed, the distribution of excited atoms

in the arc-type discharge is given by a Boltzmann distribution



ei -hs//kT
N = N. e-e (2)
m 3 g.
.3









where

N = the number of excited atoms of M per cubic centimeter;

N. = the number of atoms of M in the lower state per cubic

centimeter;

g. = statistical weight of the upper level i of energy E,

g. = statistical weight of the lower level j of energy E.;
-16
k = Boltzmann constant, 1. 37 x 101 erg/'K.;

T = absolute temperature in 'K.

By assuming that j is the ground level and substiuting Equation 2

into Equation I, the well-known Lntensity relationshup results



I = A..N hve-" /kT (3)
m iJ j-
"J


where

i = the excited level,

j = the ground level.

The value of N., the rnurrber of atoms of MI per unit volume per

unit time in the lower energy state, j, depends directly on the concern-

tratbon of hi in the orgin-al copper poa'der simple. This relationship

is e.-pres red by

N = K.C (4)
j Jm


%here KI is a proportionalty constant.








The results obtained in this research clearly indicate that

constant conditions of excitation were maintained. For this reason,

all the terms on the right hand side of Equation 3 except N. will be

constant. By substituting the value for N. from Equation 4 and by

combining the constants into one term, Equation 3 can be rewritten

in the familiar form of

I = K C (5)
m mM m

where K is an overall constant. Equation 5 is often called the
ma
basic equation of quantitative emission spectroscopy.


B. Internal Standardisation


Most modern precise methods of emission spectrochemical

analysis are based upon the internal-standard principle which was

reported by Gerlach (79) in 1925. He introduced the concept of

referring the unknown line intensity to the intensity of a line of some

other element present in fixed concentration in both samples and

standards. This method of analysis is particularly suitable for the

determination of elements present in trace amounts. The advantage

of using an internal standard is that it affords compensation, since

both lines are subject to the same uncontrollable fluctuations in the

excitation and photographic process. It is not always possible to

maintain constant excitation conditions since the effective temperature

of the discharge may vary from one determination to the next due to








variations in the gap length, the humidity of the room and the line

voltage. The quantity of radiant energy reaching the detector surface

may vary between determinations as a result of variations in exposure

time, scattering of light from optical surfaces and wandering of the

discharge image across the spectrographic slit.

The internal standard may be a matrix element or any other

element whose concentration is constant from sample to sample. In

this research weak lines of copper which were ouc.d to be constant in

intensity within the L[mits of experimental observation were used as

jnlernil standard lines. The ratio of Im, the intensity o. a cpectral

.ine of metal .1, to I the intensity of a spectral line of the int..-nil

etandard element, S, is given b1 R
m,



I I K C
R" = l " (6)


When an internal standard element S is chosen it should have an

excitation potential similar to N1 and also a similar rate of volatili-

.aticon. In addition, the analysis line of wavelength ,1 and the

internal standard Line of wavelength should be free of aed-

absorption. The analysis line and the internal ai ndard Line should

be as near the same wavelength as possible in order to minimize

variation of spectral response of the detector *with wavelength. If

the above conditions are approximately valid, then K /K is a

constant even if excitation conditions or instrumental measurement








conditions should vary during a single determination or from one

determination to the next. Also C will be a constant as long as

matrix conditions are approximately constant which is true in this

study. Therefore Km /Ks. C is a constant. Equation 6 now be-

comes

R = K Cm (7)
m, m

A plot of R versus C called a working curve, should therefore
my m
produce a curve of unit slope over concentration ranges of M in which

the above approximations are valid.

Although it is impossible to find a perfect internal standard

element or line, internal standard elements and lines can be found

for which K. in Equation 7 is valid to within + 2%. The data reported

in this dissertation indicate this to be the case.

In the derivation of Equation 3 and eventually Equation 7, it was

assumed that thermal equilibrium existed in the arc discharge, and

therefore the distribution of excited atoms was describable by the

well-known Boltzmann equation. It was also mentioned that the

Uni-arc source gives not only arc-like conditions but also spark-like

conditions, for which the Boltamann distribution probably is invalid.

However, even if the Boltzmann distribution of excited atoms were

invalid for the arc as well as the spark, Equation 7 should still be

valid to the degree of accuracy stated above. This statement can be

made since the only factor of importance in emission spectrochemical








analysis is that there exists a definite distribution of excited atoms,

the exact form of which is unimportant as long as it is reproducible.

Therefore KI in Equation 7 will be a constant for both arc and spark

lines.


C. Determinaton of .'.rc Temperature


For the measurement of an absolute temperature of an arc dis-

charge, the exact distribution of excited atoms must be known It

has been established that a direct current arc ii 3 sentially a thermal

source, therefore Equation 3 applies to the intensity of a apectral line

of metal M. The distribution of intensities encountered by electron

impact and by collisions of the second kind s;mulate thermal equil-

ibrium and therefore a value of the factor T in the Inten-ity equation

can be obtained. If the rjt;o of tie intensities of two Lines of MI is

measured anA if the cl:.'er energy level of both lines is the same,

then


1! I : (Ez 2 -E)kT (8)



In this equat on it ia ajsimed that all instrumental actors are kept

constanL during the meaniirements and that neither hne i. appreciably

Eelf-absorbed. In EquaLton 8 the subscripta I and 2 denote the lwo

spectral lines of element Ml. The other syrmbal have already been

defined. If the values of A, g, ;' and E are known for a given line








pair, the temperature can be calculated when the value for the

ratio I/IZ has been determined spectrographically. In this disser-

tation the line pair copper 5153 A. and copper 5700 A. was used for

the temperature measurement. The upper energy levels of these two

lines differ by 2.26 volts, and the ratio A x gl/A2 x g2 = 590 24.

A value of 3.15 was experimentally determined for the ratio

1515 .I5700. Substituting these values into Equation 8 gave a value

for T of 5195 100 "K. Lebedeva and Milovidova (80) reported a

value of 5550 + 140 K. for copper on carbon electrodes using direct

current excitation. This difference in temperature is to be expected

since "off" cycle cooling occurs with Uni-arc excitation.


D. Inherent Advantages of a Copper Matrix


The most important factor in determining the precision which may

be attained in emission spectrochemical analysis is the constancy with

which all the variables involved may be controlled. There are several

favorable properties inherent in copper which have contributed signif-

icantly to the precision achieved in this research. Very little line

interference is encountered due to the relative simplicity of the copper

spectrum. However a large selection of lines is available for internal

standardization. It has been found that there is a marked suppression

of fractional distillation in a copper-rich arc.








Although much of the arc radiation results from thermal ex-

citation, several excitation mechanisms are also active. Excitation

can occur by collision between neutral or excited atoms or ions and

other atoms or ions which are excited to higher excitation energies.

The copper matrix provides an abundant and constant number of excited

particles which will transfer their energy to the sample atoms on

collision. These copper atoms may be designated is e:citation energy

donors. A material which serves as an excitation energy donor must

have an excitauon potential above that oi moet metals to be determined,

yet not so far above that very fem of their atoms ire excited or ionized

relative to the number of lower ioruzatron potential atoms present.

The presence of energy-donor atoms of ionization potential higher

bthn the atoms to be excited assures that all possible excited staten

of the donor atoms are available for satisfying the requirement~ of

close energy-level matches for energy transfer to occur on collision.

In this respect the iomuation potential of copper t ranst favorable

relative to the trace elements determined in this research

The ionization potential and the liquid range are give n bn Tbe I

for copper as ,ell as the trace elements determined in this research.

The abundance of copper exciter particles increases the number of

sample-exciter-particle collision events thus creating more collision

radiation Ir this manner, copper serves as a light-emission

regulator.









TABLE I

IONIZATION POTENTIALS AND LIQUID RANGES


Element Ionization Potential Liquid Range

in electron volts M.P. 'C. B.P. "C.



Copper 7.68 1083. 2595

Chromium 6.74 1890. 2480

Iron 7.83 1539. 2740

Lead 7.38 325.6 1725

Manganese 7.41 1260. 1900

Nickel 7.61 1455. 2730

Silver 7.54 960.5 2212

Tin 7.33 231.9 2270

Zinc 9.36 419.5 906



The temperature range of the liquid state of many metals lies

wholly or partially within the temperature range of liquid copper

metal. Molten copper has the ability to dissolve large amounts of

most other metals thereby forming a homogeneous melt in the crater

before thermal feeding of the sample into the arc column. A copper

metal matrix thus allows the volatilization of many elements from a

homogeneous metallic solution.








In order to utilize as many of these favorable properties of

copper as possible, it was desirable to develop a technique which

would permit the direct analysis of the powders. There are two

distinct advantages inherent in powdered samples: one, powders

are easy to store and two, the spectral sensitivity of powders is

generally high.

In emission spectrochemical analysis standard samples are

required to establish the original relationship between intensity

ratios and concentration. The ASTM Special Technical Publication

No. 58-C, which is a report on standard samples and related materials

for spectrochemical analysis, revealed that standards were not

available for the determination of trace impurities in copper pouJders.

High quantitative accuracy is to be expected only in cases where the

standards match very closely the size, shape, chemical composition

and metallurgical history of the samples to be analyzed. 'he ne-

cessity of the similartry between the standard and the sample arises

from the fact t.i. the constituents of a : mpie are involved in the

arcing and sparking processes in a highly sensitive manner. This can

lead to varislions in light-emia~son intensities since they are de-

pendent on the relative number as Aiell as the absolute number of

atoms present, their rate of feed, the gas temperature and surrounding

atmosphere.








E. Standard Addition Method of Analysis


Before a technique for the direct analysis of copper powders

could be developed, it was necessary to obtain suitable copper powder

standards. The concentration of the elements in the various standards

must be known and should cover the complete range of concentrations

expected. At least three standards are necessary to establish

analytical working curves which are later used to complete the

analysis of the various elements in the unknown samples.

Solution standards present the fewest problems of any type of

standard used in emission spectrochemical analysis. For this reason

it was decided to establish the necessary copper powder standards by

using an analytical procedure termed the "Standard Addition Method

of Analysis. The method (81) represents a relatively simple pro-

cedure for establishing the relationship between the intensity of a

spectrum line and the concentration of the element in the sample.

The addition method is particularly applicable to situations where it

is desirable to validate the composition of some material by a method

that is self-sufficient spectrographically.

In this procedure synthetic standards are prepared by adding

known amounts of the element to be analyzed to a solution of the

sample. The data obtained for this addition series are plotted on a

regular coordinate graph, with the zero ordinate selected near the

center of the graph. If the curve is extrapolated to zero intensity, the






25

intercept of this curve with the concentration axis will give the

negative of the trace element content of the sample used as the base

of the synthetic standards. The foregoing technique is rather gen-

erally applicable to analyses requiring preliminary standardization

with synthetic standards.













IV. EXPERIMENTAL APPLICATIONS

A. Apparatus and Reagents


Source Unit. The Uni-arc component of National Spectrographic

Laboratories' source unit (Model No. KE-1234) was used in this re-

search. This unit has an auxiliary air gap in series with the

analytical gap which furnishes a controlled spark discharge. The

source conditions used in this work are given in Table II.

Arc-Spark Stand. The housing for the electrodes in this research

was a NSL Universal Arc-Spark Stand. The gap spacing is adjusted by

means of a projected electrode image which has a 7x magnification.

A rotating platform was used to hold the sample electrode during the

analysis of the solution samples. A 10 r.p.m. motor was used to

rotate the sample.

Accessory Lens. A condensing lens was placed between the

source and the slit for the purpose of focusing the image of the light

source on the prism. This ensures uniform illumination of the slit.

The optical axis was at the mid-point of the analytical gap. Mag-

nification was selected at which the arc image remained within the

collimator during the entire excitation period.
















TABLE II

SOURCE CONDITIONS




Liquid Powder

Sample Samples


Capacitance, y f. 0.0075 0. 0075

Inductance, .h. 300 35

Resistance, ohm Tione none

Spark Po'er 2 5

Arc Power 8 7

Discharges per half cycle on spark 1 4

Peak voitage, output, volta 14,000 5. 000

Auxiliary gap widLh 5 mm. 4 mm.

AnIalyucal gap wioth 3 mm I mm.

Air prese~re 2 p. a i. p. 5 .








Spectrograph. A Bausch and Lomb Large Littrow spectrograph

was used in this research. It is a prism instrument capable of

covering the wavelength region 2100 A. to 8000 A. The various

spectrographic conditions employed in this study are shown in

Table III.


TABLE III

SPECTROGRAPHIC CONDITIONS




Wavelength region 2500-3475 A.

Slit width 20 microns

Hartmann 6. 5 mm.

Intensity control device Three-step filtered
slit cover lens
10/100/65% T.

Exposure period 40 seconds


Photographic Plates. The photographic plates used in this re-

search were Kodak Spectrum Analysis Plates, No. 1. These plates

were developed especially for use in spectrographic analysis by the

metallurgical industries. They have higher contrast th-n the usual

process plates, low background density and adequate sensitivity.

Plates, from the same emalsion batch, were purchased in lots large

enough to last nine months. These plates were stored in a refrig-

erator at 40'F. Since the changes which may occur in photographic









materials with age are of a chemical nature and in general have high

temperature coefficients, storage at that temperature reduces the

magnitude of these changes.

The emulsions were calibrated in accordance with the recom-

mended practices for photographic photometry in spectrochemical

analysis (ASTM Designation: E 116-56T). Calibration curves were

drawn for hundred-angstrom intervals in order to eliminate errors

arising from the dependence of photographic contact on wave-length.

Developing Equipment. A National Spectrographic Laboratories'

processing unit was used for developing the spectrographic plates

using the conditions listed in Table IV. This unit is equipped with


TABLE IV

DEVELOPING CONDITIONS




Developer (Kodak D-19, 70r. ) 3 minutes

Stop bath ({. acetic acid) Ki second

Frxing btjh (Kodak rapid liquid fixer- 4 minutes
with hardener. 70F.)

Wash 5 minutes

RPnse Kodak photo-flo
solution

Dry forced warm air









an agitator which provides continuous agitation while developing and

fixing. The photographic solutions were maintained at a constant

temperature of 70F. by means of a thermostatically controlled water

tank. The recommended practices for photographic processing in

spectrochemical analysis as set forth in the ASTM publication E 115-56T

have been followed in this research.

Densitometer. The spectrographic plates were evaluated using

a NSL projection comparator-densitometer, the "Spec Reader. The

slit employed in this instrument has a width of 0.02 mm. and a length

of 0. 7 mm.

Balance. A Mettler M-5 Microchemical Balance with an accuracy

of _0. 02 mg. was used for all weighing in this investigation.

Glassware. National Bureau of Standards Certified Class A

volumetric glassware was employed in this research.

Electrodes and Their Preparation. All of the electrodes used

in this investigation were United Carbon ultra-purity performed

graphite electrodes. The counter electrode in all analyses was

United No. 5710. Two types of sample electrodes were used in this

research, United No. 1909 for solution analysis and United No. 105-S

for powder analysis. These electrodes are illustrated in Figure 1.

The use of a necked electrode (No. 105-S) aids in attaining higher

electrode temperature by minimizing the conduction of heat along the

electrode.























1r -77
SrE .






Top Vje*


50








5710 105-S


Figure I. United Carbon ullra-purity preformed graphite electrodes








Before the sample electrodes could be used in the solution

analysis it was necessary to seal the surface in order to eliminate

absorption of the solution by the graphite. A protective coating

material, sold under the tradename "Prufcoat, was diluted with

50 parts of spectro-grade carbon tetrachloride and applied to the

surface of the sample electrodes. The electrodes were ready for

use after they had been dried under an infrared lamp for thirty

minutes.

Reagents. A master solution was prepared from the copper powder

which was to serve as the matrix for the synthetic solution standards.

Thi matrix solution contained 10 grams of copper per liter.

All the reagents used in the preparation of the synthetic solution

standards were of the highest purity obtainable, and are listed in

Table V. Spectrographically standardized samples were used for all

the elements except chromium. This element could be obtained only

in the form of the hydrated nitrate. The acids used to dissolve the

samples were redislilled reagent grade.

A bulk solution containing 1. 00 gram of the element per 100 ml.

was prepared. These bulk solutions were used in the preparation of

copper matrix stock solutions. One ml. of the copper matrix stock

s solution contained 9. 9 mg. of copper and 0. 1 mg. of impurity element.

All succeeding solutions of the impurity elements were prepared from

this copper matrix stock solution by dilution with the matrix copper









o






0A
S "








Frk r k%




0 cl. -a
Sa a















u c v ,
53 -En 5 S
.a 0 3 3 41 40 0















40AA
0 0 a a o

*> ~a o



o 0 0 0 0 84r
40' 4'C ~ *'f 44' 44'C
US US US '.4 4Q4 US US .~ .

>- j~ S" >> >
C- C.- E3 ' 83 S

4 a 0'J 0 0e 0
- 8a 44 | 8. s a ^33 ;
- U U aa U .4 u I.
o 0 . C. .
O '4 1'1 4 4; 'j ,|



a k
U Li

c o a o d o d a .
3,(a 0 U 1) U U U J E E
Ei5 'C 1 *o t' -'3 C3
0 a c a a a .0 .0-
o .'I .1) 4 'I .1 U U
^-i 4 * . J J
.0 .0 u J U U4
U .0 g( .0 .0 .E0J5 C C
CE

11 q I 8 84

aS aa C #4 CL. a s 'S
1







4,j 5f '0 L- I "i U
& 84 4,^ S, 6, 84 -
.*o




uu

"O 3 gi -

a: s a o 2
S L : ig
5 : -S S z i- ^i r z


o
U)

o






I-









z
a


s


F'


#4







solution. All copper powders used in this research were obtained

from Greenback Industries, Inc.


B. Experimental Observations


Analytical Line Pairs. In quantitative spectrochemical anal-

ysis, the selection of suitable lines for the determination of various

elements and for an internal standard involves the study of three

major factors: interference, exposure and spectral characteristics.

A tentative selection of analytical lines for the various elements was

compiled after consulting many literature references (82-88). A

preliminary check for interference was made using the M.I. T. Wave-

length Tables.

For the most accurate work the line should fall on the linear

portion of the gamma curve. Whenever it was possible, the lines

which were chosen for internal standard lines had a value of 45% to

55% transmission. The chosen element lines had values of 20% to

80% transmission. The analytical line pairs used in this research

and their characteristics are contained in Table VI.

The spectral characteristics of the analytical line pairs under

consideration were studied with respect to their excitation potentials

(89) and their tendency for self-absorption. The reproducibility of

the intensity ratios of the analysis pairs chosen are given in Table VI.

Figure 2 is a typical example showing the distribution of the intensity

ratio about the mean.










SI:
'4
'4 |ta


5 N V r -yr T r
en Nt '- *. -" .5 -r en OJ


.0 n

'0 1 N 0' cO N Z -t i en e
o Oi C^ C N cc 0' CT' 7- t C 0 0
. f -J ,-' C C C -' C



c" Go 0B 0 c r' O)
s0 0 C) a a = a o C) D
a a -1 .n 0 C LA
oIE a C) a C) 4' Nj Ln i*
'J U? r, l l ~ l lu l l lI
o CO C C. C 0 C C C 0

c- cc o C a ao a c a a o
U o c o o aL d a



q I0 t" tE i E t': E3 6t E,- Bi |, (
a ai a a a a -o o i a
cU a 0 a co a a,








^a
Lk






-J-
CO 3 5' r- P-
fc cc - a- ,n -. ie a.


i en *o a* 3T .7. 3- ^ in cc
Wac


*O Cc a. .r N^ 0a c] 7.- '

j N N r. n w i3 ui Ln
en cc C) ao o cc cc t, cc 03 en
C N -. e OD Zn C O1 CO N


-VI U U U U U U U U U U U




-Z C. N -'- o' cO
u--


CD 1- p en a *n 5



Wa


0
a


'4
n



S
f4,



'0
N


I 1



a
'.1


E '


a t

C m


j1 a
r: v


s
a 4
' -

e C
a


L.
C
- a



OS

Si ,
g,
'4 a
* N










2.0





00 G'
N 1.0 o o


W U


0.5
4 8 12
Number of Determinations
Figure 2. Plot showing the distribution of the intensity ratio
Fe 3025. 84/Cu 3024.99 about the mean. Coefficient of variation
3.23%


Optimum Sample Size. The general consensus of most spectro-

graphers is that weighing of the sample is not necessary when internal

standardization is employed. By using electrodes of the same size,

and always filling the cavities to the brim, it is assumed that approxi-

mately the same amount of each sample will be arced (90-92). However,

in this research it was found that this was not true. Due to variations

in apparent densities of the various powders, the amount of sample

contained in identical electrodes when filled to the brim ranged from

42 to 60 mg.

Since it was known that the production powders for which this

method was developed would vary in apparent density, it was nec-

essary that a uniform sample weight be established. Optimum line








intensities were obtained from samples weighing 50 mg. The samples

were weighed directly into the sample electrode. A small electrode,

United Carbon No. 1993, was used to pack the powder firmly into the

cavity. This packing process deposited a thin layer of graphite on

top of the sample which served to prevent loss by spraying during

the ignition period.

Exposure Time and Selective Volatilisation. Moving plate studies

were performed on the copper powders to determine the variation of

the spectral intensity of impurity and matrix :Lne as a function of the

time of arcing. One element, zinc, was selectively volatilized from

the copper matrix. The other impurity elements volatilized at about

the same rate as the copper. Volatilization curves for the elements

unjar consideration are aho.wn in Figures and 4. An arcing tme of

40 seconds was chosen .,nce all of the elements had reached their

[pek ,nten-liy before the end of the .10 second period.

The oscilloacopic pattern -ev~ealed that the spark portion of the

Uni-arc had 16 breaks per half-cycle. Therefore, there were 76, 800

individual eamplings by the spirl: excitation during the arcing time

of 40 seconds. rhis accounts for the very good reprodcibility af-

forded by Uni-arc ecltatrin.

Operating Conditionc. The operating conditions which prevailed

in the soJrce during the excitation period are given in Table VIT.




























o I



6O \

60







80 -








100 '
10 20 30 40 50
Seconds

Figure 3. Volatilization curves for zinc, lead, iron, manganese and
chromium

o- Z- inc Iron Chromium
- Lead --- Manganese










0







20







40 -







1t 60
SI"

.




a '
t a \ l"




.-
80 -

P
o




100
10 20 30 4u
Seconds
Figure 4. Voairiliz aion curves for silver, nickel and tin

Sjler Nickel Tin









TABLE VII

OPERATING CONDITIONS


Liquid Samples Powder Samples


A. C. amps. 4.8 9.5

A. C. volts 180 198

R. F. amps., spark 1.0 3.0

R. F. amps., Uni-arc 7.0 7.0

A. C. line voltage 226 228



C. Procedure


The general procedure described below covers both solution and

powder samples. However, the solution method was uced only to estab-

lish the standards to be used in the powder method. The techniques

used in the analysis of both sample types differ only in sample

preparation.

Preparation of Unknown Samples. For analyses using the solu-

tion technique, a 1. 00000 gram sample was dissolved in 35 ml. of 1:1

nitric acid and diluted to 100 ml. Three drops of the solution to be

analyzed were placed on a treated electrode. A special heating

arrangement was necessary to evaporate the solution to dryness on

the electrode. The electrode was placed on a hot place which was









centered under an infrared lamp. When the solution was just

approaching dryness, the electrode was removed from the hot plate

and allowed to cool. Three more drops of the sample solution were

added to the electrode and the evaporation process described above

was again followed. This procedure was continued until 0. 1 ml. of

sample solution had been evaporated to a crystalline form. Complete

ignition to the oxides was not carried out due to the danger of losing

trace elements.

Powdered samples required no further preparation and they were

ready for analyse when they were received irom production. An

electrode holler which would maintain the electrode in an upright

pos;tjon was fashioned from a cOllulose sponge. The empty electrode

was placed in the holder ano weighed The sample w:s placed In the

electrode cavity unul a Eitnile weight of 50. 0) u.01 mg. was ob-

taned. The sample wae then carefully packed into the cavity using

a small electrode.

':pectrographic Anilyi. The source, apectrographic and oper-

acing conditions used for both E"pes of samples are given in Tables

U, III and VII respectively. In the caie of solution samples, the

sample electrodes were placed on a rotating platform. .\ measuring

period of *40 seconds was used for both powder and solution samples.

Developing. The photographic plates were developed according

to the conditions given in Table IV.









Evaluation of Line Intensities. The % transmission values for

the element and internal standard lines were determined using the

densitometer. These values are read directly from the densitometer

scale. The wavelengths for the analytical line pairs used in this

research are found in Table VI.

Calculation of Relative Intensity Ratios. The % transmission

data were converted into relative intensity ratios by the use of an

emulsion calibration curve (93). The calculation involves a calibra-

tion curve and a sliding image of the bottom scale of the calibration

curve in a manner somewhat analogous to the use of a slide rule and

its sliding scale. The 1.0 value on the sliding image is placed on

the calibration curve scale at the % transmission value obtained for

the internal standard. With the sliding scale maintained in this

position, the relative intensity ratio is the value on the sliding scale

which coincides with the % transmission value for the element on

the calibration curve scale.

Calculation of the Unknown's Concentration. After the conver-

sion of the % transmission data for the analytical line pair into a

relative intensity ratio, the concentration of metal M was determined

by the use of a working curve. The intensity ratio value is the R
my
value in Equation 7. Thus it is possible to read the concentration

of metal M directly from the working curve when the value of R

is known.








D. Eperi-nental Results


Determination of the Residual Trace Impurities in the Master

Copper Matrix Solution. The copper powder chosen for the master

copper matrix solution had a copper content of 99. 75'%. A pre-

liminary qualitative spectrographic analysis of the poaider revealed

that the following elements were present in trace amounts: alumrinun.,

antimony, chrorrum, iron, lead, magnesium, manganese, ruckel.

Lilcon. silver, and zinc. It -as foun' that the "Pr l-coat" used for

treating the electrodes prior to analysis contained contaminants of

aluminum and magnesium. Thus it was not possible to analyze for

these two elements using the solutionn technique. Since it was nec-

essary to have completely homogeneous soluuon, for the preparation

of the synthetic standard, the zcudy was restricted to those remaining

elements .iuch were soluble in nitric acid, namely chromium, iron.

lead, manganese, nucket. silver, and ainc.

The standard addition method of analysis, discussed on pages

24 anil 25. was applied to the anZlysfi of the master copper matrix

solution. By making appropriate dilutions of the copper matrix stock

aolutiona (containing 9 9 mg of copper and 0. I mg. of impurity ele-

menr per ml ) with the matrix copper solution, a series of standard

addition solutions was prepared. The addition solutions were ana-

lyzed by the method for solu.on analysis outlined in the preceding

Fection. The data obtained for the addition series and Listed in









Tables VIII-XIV were used to determine the concentrations of the

residual impurities present in the matrix copper solution. Figure

5 is a typical example of a standard addition curve used in extra-

polating to the residual concentrations. The results obtained for

the analysis of the matrix copper solution are found in Table XV.

Analysis of Production Batches 333. 1932 and 2145 by the Solu-

tion Technique. The true concentrations of the addition solutions,

found in Table XVI, were calculated from the residual data obtained

for the matrix copper solution. Synthetic tin standard solutions

were prepared by the direct addition of bulk tin solution (containing

just enough hydrochloric acid to keep the tin in solution) to the matrix

copper solution. This direct preparation of tin standards was possible

due to the absence of tin in the matrix copper solution.

Analytical working curves for solution analysis were constructed,

using the synthesized standard solutions. These working curves are

given in Figures 6-8. The results obtained for Batches 333, 1932,

and 2145 are given in Table XVI. These powders and the master

copper powder were analyzed by the direct powder technique and the

data thus obtained were used to construct analytical working curves

for direct powder analysis. The working curves are shown in

Figures 9-11.










TABLE VIII

CHROMIUM ADDITION SERIES


Sample Number af Average Intensity Coefficient of
Determinations Ratio Variation. %


Matrix
Solution 10 0.77 1.62

0.00125% 10 1.02 2.36

). 100 50% io 1.2 8 3.71

0. 0050)0 10 1.77 1.77






TABLE IX

IRON ADDITION SERIES


Sim3ple Number of Average Intensity Coefficient of
Determnation- Ratio Variation, 7.


M.tatrix
cliution 10 0. 39 08

0.010% 10 0.53 3.45

0 0'2% 10 0.70 i.1

0.0500 10 I. 13 0.58













TABLE X

LEAD ADDITION SERIES


Sample Number of Average Intensity Coefficient of
Determinations Ratio Variation, %


Matrix
Solution 10 0.69 5.78

0.025% 10 0.85 4.27

0.050% 10 1.02 4.02






TABLE XI

MANGANESE ADDITION SERIES


Sample Number of Average Intensity Coefficient of
Determinations Ratio Variation, %


0.00125% 10 0.59 3.24

0.00250% 10 0.85 1.36

0.00500% 10 1.38 2.49













TABLE XII

NICKEL ADDITION SERIES


Sample Number oi Average InLenayry Coefficient of
DeterminatJone Ratio Variation, .'


0.00125% 10 0.61 5.61

0. 00250,t 10 0.70 4 56

0.C0500. 10 0 8'? 2. 37







TABLE XI1I

I3LVEI: ADDITION SERIES


SanmpLe Number of Average Intensity Coeificient of
Determination Ratio Variation, %


Matrix
Soluiton 10 I. 10 4. 15

0. 00050%'' 10 1.60 0. 78

0.00125% 10 2. 32 1.47









TABLE XIV

ZINC ADDITION SERIES


TABLE XV

ANALYSIS OF MATRIX COPPER SOLUTION


Element % Concentration


Chromium 0.00380

Iron 0.0263

Lead 0. 1027

Manganese 0.00151

Nickel 0.00658

Silver 0.00110

Zinc 0.0568


















































u.u U.- 0.8 I 2 1.b 2.
Intenainy Eatio Cr 2835.63/Cu Z84o. 48

Figure 5. Extrapollabon to the reaidual chromium concentration in the
master copper matrix solution











TABLE XVI

TRUE CONCENTRATIONS OF THE FIFTY-FOUR
SYNTHETIC SOLUTION STANDARDS


Chromium (%) Iron (%) Lead (%) Manganese (%)


0.00380 0.0263 0. 1027 0.00151

0.00505 0.036: 0. 1277 0.00276

0.00630 0.0463 0. 1527 0.00400

0.00880 0.0763 0. 1827 0.00650

0.01500 0. 1100 0.2300 0.00900

0.03800 0.1800 0.3000 0.01500

- - 0.2500 0.4000 - -


Nickel (%) Tin (%) Silver (%) Line (%)


0.00658 0.0100 0.00110 0.0568

0.00783 0.0600 0.00160 0.0668

0.00908 0.1100 0.00235 0.0968

0.01158 0.1800 0.00360 0. 1168

0.04000 0.2500 0.00610 0. 1800

0.08500 0.3200 0.00860 0.2500

0. 12000 0.5000 0.01110 - -
























































Figure 6. SoluLion
chromium


Ni 3050.82
Cu 3044.03






Cr 2815.63
Cu 28b46.48


0.5 1.0 2.0 3.0

Intensely RaUO

uorkmng curves for nickel, manganese and


0.0200






0.0 100


0.0050


0.0020 p


0.0010


I i I I I,
















0.0100







0. 0050 Ag 3382.89
0.005 Cu 3384.83










0.0020 -








0.0010 I I I I I I
1.0 2.0 5.0 10.0
Intensity Ratio

Figure 7. Solution working curve for silver















0.500


Sn 2850. 62
Cu 2858. 73

Pb 26b). 17
C/ 2/63U.00
0.200 /
/ /
d
" .'


0 100 .

-- /
SLZn ,145.02
' Fe OZ3020.64 / C 3354.47
Cu 3022 16I
0 050



/




0.020 i
0.2 0.5 1.0 2.0 ,.0
Intenfly Ratio

Figure 3. Solution a'orki-,g curves for tin, lead, iron and ainc















TABLE XVII

ANALYSIS OF PRODUCTION BATCHES 333, 1932 AND 2145


Element Concentration

B-333 B-1932 B-2145


Chromium 0.00420 0.00420 0.00493

Iron 0.0670 0.0725 0.1070

Lead 0. 1300 0. 1110 0.2000

Manganese 0.00227 0.00216 0.00467

Nickel 0.0463 0.0350 0.04 1

Silver 0.0056 0.0054 0.0060

Tin 0. 1930 0. 1630 0.2380

Linc 0. 1320 0. 1080 0.2250


Copper 99.30 99.34 98.98
























Fe 3025.84
Cu 3024. 99



//
/
/


S Ni 05u. 82
SC. 3088. 13


SIi I I I I


0. 1500 r


0. 1000


0.0500


0.0200 -


0.01


u.2 u.5 1.0 1.
Intensity Ratio

Figure 9. Powder working curves for iron and nickel


0



























Sn 2850. 62
Cu 2858. 73

Pb 2823. 19
Cu 2858. 23




Zn 3345.02
/ -Cu 3354.47
/ /


/


0.0200 I I I I I I -
0.0200
0.3 0.5 1.0 2.0 4.

Intensity Ratio

Figure 10. Powder working curves for tin, lead and zinc


0.4000 -


0.2000 -


0. 1000


0.0500


"


"















0.0100


0050


Cr 2865.63
Cu 2846.48
A


/ Mn 2794. 82
- C.u 2846.48


0. 0020Ik


0.001 0 1 I i I II
O .O J iO~ -- - '- '-- '- '----- -- ---- '
0.5 i 0 2.0 3.0

Intensity Ratio

Figure 11. Powder working curves for chromium and manganese





58

Analysis of Production Batch 2094 y the Solution and Powder

Techniques. Production Batch 2094 was analyzed by both the solution

and powder techniques. The results are found in Table XVIII.


TABLE XVIII

ANALYSIS OF PRODUCTION BATCH 2094



Element Solution Powder Relative
Technique Technique Difference (%)


Chromium 0.00251 0.00250 0.40

Iron 0.0904 0.0910 + 0.66

Lead 0.0972 0.0980 +0.82

Manganese 0.00199 0.00199 0.00

Nickel 0.0267 0.0268 + 0.36

Tin 0. 1476 0. 1470 0.40

Silver 0.00578 - - - -

Zinc 0.1254 0.1248 0.48


Copper Content 99.40



E. Discussion of Results


Theoretical working curves will show a 450 slope on a logarith-

mic plot. This 450 slope indicates the following: (1) the percentage

values for the standards are correct, (2) strict proportionality exists








between intensity ratios and concentrations, (3) background is in-

significant (94).

In this research, the linear portion of all the working curves

possesses a slope in the rang-e of 43-47*. Twelve of the curves are

linear over their entire concentration range. The remaining four

curves exhibit slight curvature near their upper limits. This curvi-

ture is probably due to self-absorption in the impurity analy.Ls line.

A background correction was not applied to the working curves be-

cause the background traDmnission was greater than 95,7 in the areas

adjoining the dpectral lines under study.

An enhancement of .pectr:l line intensity in the powder method

madu it necessary to use different analytical Line pairs for iron and

lead from those used for the solution method. A new line, suitable

for use as an analysis Line, could not be found for silver in the 2500-

.-100 r.. region. Therefore, a powder working curve for silver is not

available.

All precision data are given in terms of coefficicnt3 of variation

( 5) which were calculated as follows


100 2/ d2
c -j n -
where c = average intensity ratio

d = difference of determinations from mean

n number of deterrunations.





60

It should be noted that the average value for c was approximately 1. 00.

Thus the standard deviations of the results are almost 100 times

smaller than the coefficients of variation. The average coefficient

of variation for all the intensity ratios was 3%. Since all the work-

ing curves approached very closely the ideal 45 slope, the results

in terms of concentration have the same reproducibility.

Due to the fact that the powder standards were established using

the solution technique, the accuracy of the powder method is no

better than that of the solution method. Nevertheless, the ease of

sample preparation in the powder method makes it a much more

rapid procedure than the solution method.













V. SUT.t LARY


A new quantitative method for the emission spectrochemical

determination of residual trace impurities in sponge copper powders

has been proposed. The method is rapid, accurate and requires a

rruumum amount of sample preparation.

The lack of available powder standards made it necessary to use

a method uhich was sell-sufficient spectrographically to validate the

composition of the five powder which were to serve as standards in

the powder method. A solution technique utiL:iing the standard addition

method of analysis was used for this purpose.

The powder method consisted of weighing the powder directly into

the cavity of a preformed graphite electrode and analyzing it Mil-.

iUn-arc excitation. The copper matrix of the inample afforded many

inherent advantages and provided an excellent source of internal stan-

dard lines.

Eight residual trace imputides --chronuaum, iron, lead, man-

ginese, unckel, tin, silver, ani zinc--were determined in several

copper ponders. The accuracy and precision of thz method -was

Limited primarily by the inherent error of about 3% associated with

the photographic techniques employed.













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67


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BIOGRAPHICAL ITEMS


Anna Margaret Yoakum was born January 13, 1933, in Loudon,

Tennessee. In May, 1950 she was graduated from Alcoa High School,

Alcoa, Tennessee. She attended Maryville College from 1950 to

1954 and received her Bachelor of Arts degree in Chemistry, cum

laude. In 1954 she enrolled in the Graduate School of the University

of Florida. She received the degree Master of Science in June of

1956.

From September, 1956, until June, 1959, Miss Yoakum was

employed by Greenback Industries, Inc., as head of the Chemical

Department. For two years of this time, she pursued advanced

graduate studies at the University of Tennessee. From June, 1959,

until the present time she has continued her work toward the

degree Doctor of Philosophy at the University of Florida. While

at the University of Florida she has held positions in the Department

of Chemistry as graduate assistant and research assistant. During

the summer of 1960 she was a Graduate School Fellow.

She is a member of the American Chemical Society, the Society

for Applied Spectroscopy, the Southeastern Association of Spectro-

graphers, Gamma Sigma Epsilon Chemical Fraternity, The Society

of the Sigma Xi, and Phi Kappa Phi Honorary Fraternity.
68














This dissertation was prepared under the direction of the

chairman of the candidate's supervisory committee and his been

approved by all members of that committee. It u s isbmiled to

the Dean of the College of Arts and Sciences and to the Graduate

Council, ani was approved as partiaL ludillment of the requirements

for the degree of Doctor of Philosophy.


August 13. 1960



Dean, College o Arts aftd Sciences




Dean. Graduate School

supervisory Commiitee




Chairman











Si I




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