INDUSTRIAL a n d ENGINEERING CHEMISTRY
ANALYTICAL EDITION
VOLUM E 18, N U M B ER 7 ISSUED JU L Y 23, 1946 C O N SE C U T IV E N U M B E R 14
EDITOR: WALTER J. MURPHY
Assistant to Editor: N . A . PARKINSON Associate Editor: La w r e n c e T. Ha l ie t t C ontributing Editor: R. H . MÜLLER
Assistant E d ito rs
M anuscript Editing: G . GLADYS GORDON M anuscript R eview ing ; STELLA ANDERSON M ake-up: CHARLOTTE C . SAYRE
A d v is o ry Board,
R. P. CHAPMAN T. R. CUNNINGHAM R. H. MULLER
J . R. CHURCHILL G . E. F. L U N D E L L B. L . OSER
B . L. CLARKE M. G. MELLON H . H . WILLARD
Spectrographlc Analysis of Zinc-Base A llo ys . . . . Leslie Larrieu 403 Preparation of Synthetic Samples of Low-Boiling Hydrocar
bons . R. H . Busey, G . L. Barthauer, and A . V . M e tie r 407 Method for Calcium-Sequestering Value of Phosphate Water
Conditioners...- ...
B. C H a ffo rd , Fred Leonard , and R. W . Cummins 411 Radioactive Studies
Analytical Procedure for Measurement of Radioactive Arsenic of 90-Day H a lf - L if e ...
F. C . H e n riq u es, J r ., and Charles M argnetti 415 Analytical Method for Determination of Long-Life Carbon
O * . . . F. C . H enriq ues, J r ., and Charles Margnetti 417 Analytical Procedure for Measurement of Radioactive
Hydrogen (T ritiu m )...
F. C . H e n riq u es, J r . , and Charles Margnetti 4 2 0 Determination of Hydroperoxides in Rubber and Synthetic
Polym ers... H . A . Laitinen and J . S. N elson 4 2 2 Separation of Calcium from Magnesium by Oxalate Method
in Samples of High Magnesium-Calcium R a t i o ...
E. R. W rig ht and R. H . Delaune 4 2 6 Systematic Polarographie Metal Analysis . James J . Lingane 4 2 9 Calculation of Specific Dispersion of Pure Hydrocarbons and
Petroleum Fractions . . . M . R. Lipkin and C . C . M artin 433 Determination of Copper in Cast Iron and Steels with Quin-
aldic A c i d Jo h n F. Flagg and Don W . Vanas 4 3 6 Determination of Rubber Hydrocarbon by Gravimetric
Rubber Bromide Method ... ' ...
C . O . W illits , M . L. S w a in , and C . L. O g g 4 3 9 Determination of A lk y l Disulfides in Absence and Presence
of M e rca p ta n s...I. M . Kolthoff, D. R. M ay, Perry M o rg an, H . A . Laitinen, and A . S. O 'B rie n 44 2
Higher Aliphatic A c id Chlorides...
t Robert R. A c k le y and G iu lia n a C . Tesoro 44 4
M IC R O C H E M IST R Y
Thiocyanate Complex as Means of Extracting Cobalt before Its Microdetermination by Other M eth od s...
N . S. Bayliss and R. W . Pickering 4 4 6 Small Glass Center-Tube Fractionating C o lu m n ...
E. A . Naragon and C . J . L e w is 44 8
N O T E S O N A N A L Y T I C A L P R O C E D U R E S
Mercury Cleaning Apparatus for Continuous Operation. . Fred eric E. Holm es 451 Assay of H y d ro q u in o n e ... ...
I. M. Kolthoff and Thomas S. Lee 4 5 2
Constant-Level Feeder for Thermostatic Baths and Continuous Evaporators . . . M. S. Telang 453 Adsorption Apparatus without Stopcocks for Use with
Hydrocarbon G a s e s... C . B. W e n d e ll, J r . 45 4 Rapid Qualitative and Quantitative Determination of
Barbiturates from Postmortem Specimens . Paul V alo v 4 5 6 Micro-Kjeldahl Determination of Nitrogen in Gramicidin
and Tryptophan ...
Law ren ce M. W h ite and G e ra ld in e E. Secor 45 7 Method for Purifying Beta-Picoline and Test for Purity . .
G eo rg e Riethof, Sidney G . Richards, Sidney A . Savitt, and Donald F. O thm er 4 5 8 Modified Gate V alve for Control of Water Flow . . . .
G . Ross Robertson 4 5 9 B O O K R E V IE W S ...4 6 0 C O R R E S P O N D E N C E ...4 6 0 Instrumentation in Analysis. . .R. H . M uller (Advt. Sect.) 21
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W. M. W ELCH M ANUFACTURING COMPANY 1515 Sedgwick Street
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20. G EO R G E T . W A LK ER COMPANY 324 F ifth Avenue South
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IN ORIGINAL PACKAGES
July, 1946 A N A L Y T I C A L E D I T I O N 5
N o w am ple stocks o f Pyrex b ra n d Ball and Socket J o in ts are available in all sizes.
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July, 1946 A N A L Y T I C A L E D I T I O N
D eterm inations of c o n cen tratio n s of ihrRurity elem ents, often dow n fto one p art p er million or less, a r e ro u tin e lor the A. R. LiX ^o-m eter, g ra tin g spectrogV iph.
This instrum ent, .a n n o u n c e d u n d e r the trad e name"-«] A. R. L . D ietert s to le months ag o , is p ro v in g in p ra c tic e to b e truly the "S p ectro g tsR h er's S p ectro g rap V D esigned in e v ery a s p e c t to p rovide b e tte r a n d m ore convenieiiN sjsectrochem icd an aly sis, it is the id e a l in stru m en t for difficult control a n a ly s is or res^CKqh w o rk \
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I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 18, No. 7 AWUA/VVWVVVVX^\Wl/VVVWVVV/VAA1AWWyAA/W\AAAVVAAAVVAVV/\AVVAaWWVAAAA\W\AWVAVVVV»A/lWl'/VVAAA/
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GLYCERINE P R O D U C E R S ’ A SSO C IA T IO N
295 M adison A te ., N e w York 17, N . Y. Research H eadquarters, Chicago, III.
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July, 1946 A N A L Y T I C A L E D I T I O N
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12 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 18, No. 7
Timely R E I N H O L D Books
ADVANCING FR O N TS IN C H E M IS T R Y
Vol. I: High Polymers Vol. I I : Chemotherapy
Edited by
W ENDELL H. POWERS,
A ssistant Professor of Chemistry, Wayne University, Detroit, MichiganA series of lectures sponsored by Wayne Univer
sity under the d irection'of Neil E. Gordon, C hair
man, Departm ent of Chemistry.
This volume is comprised of six papers by eminent authorities on various aspects of chem otherapy w hich is the science of treating infections w ith chemical agents w ith o u t harmful effects on the patient. Tuberculosis, antispasm odic agents, pari- sitic diseases, the chem istry of sulfa drugs, and the use of organom etallic compounds, such as those of gold, silver, antim ony and arsenic are discussed exhaustively in a high ly com petent manner. It should be of interest and immediate value to all chemists, biochem ists, physicians, pharmacists, bacteriologists and pathologists. Instructive read
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155
Pages Illustrated $3-50
T H E E L E C T R O N M IC R O SC O P E
Second E dition, R evised an d Enlarged
E. F. BURTON,
Head of Department of Physics, University of Torontoand W. H. KOHL,
Formerly Chief Engineer, Regers Radio Tubes L td ., TorontoA completely revised volume covering all significant advances in the field. This follows the notably success
ful first edition of The Elektron M icroscope. The new edition includes, detailed descriptions of improved types of electron microscopes, and new techniques for examining colloidal substances. Contains 23 full-page plates, some of w hich are among the most strik in g electron m icrographs ever published. Chemists, physi
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325 Pages Illustrated $5-00
C O LLO ID C H E M IS T R Y
T h eo retical and A pplied
By selected international contributors, collected and edited by
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V O LU M E V I: 71 p a p e rs co v e rin g te c h n o lo g ic a l a p p lic a tio n s w ith sp ecial e m p h asis o n plastics
P art I of Volume VI is comprised of 38 chapters, ranging in subject m atter from dyeing to drilling muds.
Tw o of these arc continuations of subjects treated in volume five and one of them is virtu ally a small book in itself on the colloid chem istry of alginates. O ther topics are soil stabilization, adhesives, insecticides and activated carbon.
P art II of Volume VI is devoted to the colloidal aspects of plastics and synthetic polymers. All of the better known types of plastics are treated from the theoretical and the practical standpoints. These chapters, invaluable to plastic chemists and technologists, conclude w ith an interesting article on nuclear fission w hich touches upon several previously overlooked points.
1230 Pages Profusely Illustrated $20.00
REINHOLD PUBLISH IN G CORPORATION
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M ethods [formerly M eta ls and A llo y s), and Progressive Architecture — Pencil Points
A series of lectures sponsored by Wayne University
under the direction of Neil E. G ordon, Chairman, Departm ent of Chemistry.
E dited by
SUMNER B. TWISS,
Department of Chemistry, Wayne UniversityThis is a correlation of diverse experimental infor
m ation concerning high polymers. It offers a logical, if lim ited, development of the recent chem istry of high polymers w hich w ill be of interest to beginners as w ell as trained investiga
tors. Covers: direct and indirect evidence for the free radical mechanism of addition polym erization;
the importance of chain length and size d istribu
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geom etry of long-chain molecules and the effect of interm olecular forces as illum inated by x-ray diffraction studies; mechanical properties of the concentrated solutions of chain polymers. Presents the ultim ately practical w ork w hich has been accomplished w ith the natural polymers — silk, cotton, and wool.
196 Pages Illustrated $4-50
July, 1946 A N A L Y T I C A L E D I T I O N 13
THE MACBETH pH METER
LINE OPERATED
CONTINUOUS INDICATING DIRECT READING
Line operated. No batteries whatsoever. Can be left on continuously. Direct reading—only one operating control.
Large, easily read scale. Range from 0 to 14 pH. Untrained users can make ordinary pH measurements. Only one lead from the two electrodes to the Meter. Electrodes may be easily replaced individually.
W r ite fo r bulletins
M A C B E T H C O R P O R A T I O N
227 W E S T 17
t hS T R E E T . . . . N E W YO RK 11
,N . Y.
M a n u fa ctu re rs o f Scientific A p p a r a tu s since 19 IS
14 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 18, No. 7
Dü PONT
H f f l C H L O R O i r a O H E X i l
Another Forward Development in Insecticides
HEXACHLOROCYGLOHEXANE is a new and outstanding insecticide. In the annual H u rter M emorial Lecture, delivered on M arch 8, 1945, by Dr.
R. E. Slade, Research Controller of Im perial Chemical Industries, he stated, ’'T here has now come to light what promises to he one of science’s im portant contributions to the welfare of m an.” Dr. Slade referred to H exachlorocyclohexane which was developed as an insecticide by Imperial Chemical Industries under the following additional names: benzene hexa- chloride, 666, and Gammexane.
Du P on t has confirmed the British records of efficiency of this rem ark
able insecticide in its, own laboratories, and is privileged to announce it has Hexachlorocyclohexane available this season in lim ited quantities for experim ental use. Inquiries from research institutions and qualified in
vestigators are invited; a copy of Dr. Slade’s lecture will be mailed on request. Grasselli Chemicals D epartm ent, E. I. du P o n t de Nem ours &
Company (Inc.), W ilm ington 98, Delaware.
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16 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 18, No. 7
5878-D. G as Analysis A pparatus, O rsat P o rtab le, A. H . T. Co. Specification, as above described, consisting of 100 ml m easuring b u re tte w ith all-round graduations a n d w ith w ater jack et, 125 m l asp irato r bottle, th ree absorp
tio n p ip ettes — tw o filled w ith glass tu b es an d one w ith glass tu b es containing copper spirals — an d m anifold provided w ith four glass stopcocks; w ith No. 121A ball-and-socket ground glass jo in ts betw een th e m anifold an d th e p ip ettes an d betw een manifold an d b u rette, held securely by new ty p e P inch Clam ps. Com plete w ith necessary ru b b er bulbs an d tu b in g for asp irato r b o ttle connection, in anodized alum inum case w ith rem ovable fro n t and back p an els... 76.25 Code o r d ... H ykuw
5872. G as A nalysis A pparatus, O rsat P o rtab le, identical With above b u t w ith ru b b e r tu b in g connections betw een th e m anifold an d th e th ree p ip ettes an d betw een th e m anifold and b u rette. W ith ru b b er bulbs an d tu b in g for asp irato r b o ttle connection. In anodized alum inum case w ith rem ovable fro n t an d back p a n e ls .. . 59.75 Code W o rd ... Hxjgeh
ARTHUR H. TH O M A S COMPANY
R E T A IL — W H O L E S A L E — E X P O R T
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INDUSTRIAL and E N G IN E E R IN G CHEMISTRY
Spectrographic A nalysis of Zinc-Base A llo y s
L E S L IE L A R R IE U , Morris P. Kirk & Son, Inc., Los Angeles 23, Calif.
A rapid and accurate spark spectrochemical system incorporating the use of the ammonium chloride-packed electrode and the flat disk self-electrode has been developed. A commercial high- voltage spark source unit with extra inductance is used for excitation of flat disk samples on a Petrey spark stand. A grating spectrograph is employed. Comparator-densitometers are used for transmission measurements and conversion to intensity ratios is made on cal
culating boards. The system provides for simultaneous evaluation of all xinc alloy constituents and impurities quantitatively on one spectrogram. The method accurately measures lead in the range of 0.002 to 0.015, tin 0.002 to 0.015, cadmium 0.002 to 0.010, magnesium 0.01 to 0.10, iron 0.01 to 0.10, copper 0.75 to 3.25, and aluminum 3.50 to 4.50% .
T
H E accurate and com plete analysis of zinc-base alloys for all alloy co nstituents and im purities b y chemical m ethods is tedious, tim e-consum ing, and often subject to serious discrepancies. U sing th e accepted chemical m ethods of analyses for this type of alloy, rapid routine determ inations are difficult, since the chem ist often has to approach his analytical problem s as if they were of um pire quality. F o r some analyses he has to use large sam ples, m ake m ultiple precipitations, exercise the utm o st care, and hope th a t his result tru ly represents his sample.
Zinc-base alloys are m anufactured under one of th e closest specification allowances of an y alloy blended to d ay ; th e speci
fication prohibits th e presence of m ore th a n 0.005% cadmium and sim ilarly low am ounts of tin and lead in th e alloy. T he spectrograph therefore offers em ancipation from th e drudgery of difficult and som etim es questionable chemical analyses.
Two and a half y ears ago th e laboratories of Morris P. K irk & Son, Inc., subsidiary of th e X ational Lead C om pany, acquired spectrographic equipm ent for the express purpose of controlling the production of nonferrous m etals and alloys.
These alloys consist of tin-base, lead-base, zinc- base, and a wide range of alum inum alloys.
Today over 75% of all these analyses are m ade spectrographically, th a n k s largely to th e de
velopm ent of a special, b u t simple, electrode.
T his special electrode (Figure 1) introduces amm onium chloride into the spark discharge from its tip, w here the sa lt has been placed in a hole drilled in th e electrode tip. These a m monium chloride-packed electrodes are proc
essed from N atio n al C arbon C om pany “spectro
scopic carbons” by m eans of a special cu ttin g tool, w hich sim ultaneously fashions a hem i
spherical tip an d drills a holeO.156 cm. ( Vie inch) in diam eter an d 0.234 cm. (‘/a* inch) in depth.
This cu ttin g tool is chucked in a high-speed electrode m achine, which contributes ease and speed to q u a n tity production of electrodes.
The electrode m ay be prepared w ith o u t the sendees of th e special tool by cu ttin g a hemi
spherical tip w ith a sta n d a rd tool, then slightly blunting "the lip w ith a fine file and by m eans of a '/» -in c h drill, m ounted in a sleeve, drilling the hole to the desired d epth. I t is essential th a t care be observed in electrode fabrication concerning the position of the periphery of th e tip. T h e electrode tip, as o u t
lined by the periphery of the drilled hole, m ust be a t rig h t angles to the side of th e electrode; if this condition is n o t a tta in e d the spark becomes deflected and produces an irregular p a tte rn on the sam ple disk. T his deflection invariably causes discordant results. However, a cu ttin g tool w ith the drill m ounted in the center of the cu ttin g blades produces a perfectly form ed electrode, requiring no fu rth er corrections.
T he spectrochem ical system of analysis em ployed for the production control of the zinc-base alloys has been chosen for presentation here, ra th e r th an o th er problem s handled by this m ethod, because of th e unusual requirem ents in analysis of high and low levels of alloy content and th e very low level of im purities allowed. All constituents, alloying elem ents, and im purity elem ents are evaluated as a sim ultaneous q u a n tita tiv e estim ation on one spectrogram .
T he alloy u n d er discussion, often referred to as N o. 2 Zamak, contains alum inum 3.50 to 4.60% , copper 2.50 to 3.50% , m ag
nesium 0.02 to 0.10% , iron 0.10% m axim um , cadm ium 0.005%
maxim um , tin 0.005% m axim um , and lead 0.007% m axim um . T h e literatu re offers few spectrochem ical m ethods for th e analysis of th is ty p e of alloy. Indeed, for th e zinc-base alloys no m ethod, including th a t of th e A .S.T.M ., provides for th e q u a n tita tiv e determ ination of alloy constituents and th e very low concen
tra tio n s of allowable im purity elem ents in a single spectrographic operation, involving th e spark technique. T h is is accom plished w ith th e flat disk technique utilizing th e P e tre y sp ark stand, am m onium chloride-packed counterelectrode, and high-voltage spark source w ith ex tra in
ductance.
T he m ethod em ployed in the spectrochem ical analysis of zinc-base alloys involves sam ple pro
curem ent an d preparation, electrode p rep ara
tion, excitation of sam ple and registration of spectral lines, film preparation, densitom etry, and calculations.
S A M P L E S A N D P R E P A R A T I O N
r
Samples for analysis may’ be specim ens of any convenient size th a t have sufficient dim ensions to re s t on the P etrey stand. However, chill- cast disks m easuring 2.5 inches in diam eter an d 0.5 inch in thickness have been found conveni
e n t to process in the laboratory. Figure 2 is a photograph of chill-cast disk an d packed elec
trode. D ie castings, p a rts of gates, sprues, and sawed slices from m etal ingots have been utilized as sam ples for this ty p e of alloy. N on
destructive analyses are often m ade on sm ooth casting surfaces w ith surprising accuracy. How
ever, sta n d a rd practice in this laboratory is to im p art a sm ooth surface to each sam ple by m eans of the lath e cu ttin g tool.
Figure 1. Hollow-Tipped Special Electrode
403
404 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 18, No. 7
•- -■■ ■• " tz * *
r*
' . » .Figure 2. Chill-Cast Dish and Packed Electrode
In te n sity ratio
intensity ratio -
P b 2833 A. + background Zn 2760 A. + background
background at 2833 A.
intensity ratio
Zn 2670 A. + background Pb 2833 A.
Zn 2670 A + background
S P A R K E X C I T A T I O N C O N D I T I O N S A N D F IL M D E V E L O P M E N T
T h e special, hollow-tipped electrode is packed w ith th e am m onium chloride sa lt by tam ping it into a dish of the ground sa lt an d sm oothing flush w ith the periphery tip by m eans of a sp a tu la or fine file. T he fully p repared electrode is then placed in the lower clip-holder of th e P etrey sta n d a n d ad ju sted for a 3-mm. gap by th e swing-away gage. T he sm oothly m achined disk, ingot slice, or casting segm ent is placed on th e sta n d as the upper electrode.
T he A .R .L .-D ietert, high-voltage spark u n it is se t a t full power (2 kva.), an d use is m ade of an additional inductance so th a t 1.46 m illihenrys arc available for the system . E xcitation is m ade on an A .R .L .-D ietert grating spectrograph possessing a dispersion of 7 A. per m m . Two 30-second sparking operations are perform ed on different p a rts of th e sam ple surface. A new electrode is used for each excitation and th e two 30-second exposures, w ithout prespark, are superim posed on one spectro
gram .
R egistration is m ade on E astm an Spectrum No. 2 film which is processed 3 m inutes in D19 developer a t 16° C. T h e film is taken through all stages of processing under constant-tem pera- tu rc conditions an d in rocker-t.ype developer trays. A new electrode is em ployed for each 30-second excitation to give identical conditions of superim position, because it w as found desirable to m aintain m axim um gassing conditions over th e full 60 seconds of sparking. P resp ark is elim inated, because of the initial v o latility of such elem ents as cadm ium an d lead.
T h e film calibration curve is obtained by s arking a stan d ard iron sam ple for 1 m inute, using the step-sector m ethod. A single screen of 200-mesh wire cloth is placed before the lens to lessen th e intensity an d th e high inductance u n it is m aintained in the circuit w ith o u tp u t pow er dropped to 4 /3 kva. Transm ission values are selected from the 2800 to 3000 A. region, and a plot of these d a ta on log-log paper, using transm issions as ordinates and intensities as abscissas, derives th e film calibration curve.
D E N S I T O M E T R Y A N D C A L C U L A T I O N S
An exposure of one m inute for zinc alloys produces a back
ground w hich h as to be accounted for in th e calculations and the accurate m easurem ent of th e difference betw een line w ith under
lying background, and background is utilized to m easure the extrem ely sm all percentages of tin, cadm ium , and lead en
countered. D ensitom etry, therefore, includes m easurem ent of transm ission values for line plus background an d ad jac en t back
ground. T he in tern al sta n d a rd m ethod of q u a n tita tiv e analysis is em ployed an d all transm issions are referred to th e 2670 A.
zinc internal sta n d a rd line. All films are m easured on tw o A .IL L .-D ie te rt com parator densitom eters w hich are used in ter
changeably.
C alculations are m ade on calculating boards, an d each elem ent’s spectral line, w ith underlying background an d average adjacent background, is com pared' w ith the in te rn a l zinc line plus back
ground.
A simple su b tractio n of background intensity ratio , from line plus background intensity ratio, gives th e line in ten sity ratio corrected for background. N o effort is m ade to m easure the in ten sity of th e 2670 A. zinc line w ithout background, since this line’s background in ten sity becomes a co n stan t in th e calculation, an d can be included w ith line in ten sity for all ratio derivations.
A schem atic presentation for th e 2833 A. lead line is:
B ackground readings, after som e experience and practice, are made rapidly and th e calculation of d u al in ten sity ratios w ith a simple su b tractio n does n o t m aterially burden th is phase of the analysis.
F o r th e analysis of the copper-bearing, zinc-base alloys the following spectrum elem ent lines have been found satisfactory:
Â
.
Z in c ( in t e r n a l s ta n d a r d ) 2G70
C a d m iu m 22 8 8
L e ad 2833
M a g n e s iu m 2 9 2 8 .7
I r o n 29 6 7
A lu m in u m 3 0 6 0
T in 31 7 5
C o p p e r 31 9 4
Figure 3. Working Curves Derived from Spectrochemical Data of Table II
Curves are v alid fo r quantitative determ ination o f alum inum and co p p er In N o s. 2 and 5 Zam ak and fo r quantitative determ ination o f magnesium, iron,
le a d , tin , and cadmium in N o s. 2 , 5 , and 3 Z am ak
July, 1946 A N A L Y T I C A L E D I T I O N 405
Table I. Typical Transmission Data, Lot 2142
T r a n s m is s io n o f lin e p lu s b a c k g r o u n d
T ra n s m is s io n o f b a c k g ro u n d I n te n s i ty r a t io - li n e p lu s b a c k
g r o u n d
I n te n s i ty r a t io o f b a c k g ro u n d I n te n s i ty r a t i o o f lin e
Z in c, C a d m iu m , L e a d , M a g n e s iu m , I r o n , A lu m in u m , T in , C o p p e r , 2 6 7 0 Â . 22 8 8 Â. 28 3 3 Ä . 2 9 2 8 .7 Â. 2967 Â. 3 0 6 0 Â. 3 1 7 5 Â. 2194 À.
1 1 .4 4 3 .5 3 5 . 7 2 2 .8 4 5 .5 4 3 .5 6 4 .3 3 9 .9
5 6 . 0 4 3 . 0 7 1 .0 6 4 .0 6 8 .0 7 0 .5 7 1 .0
0 .2 8 0 0 .3 5 0 0 .5 4 5 0 .2 8 7 0 .2 7 8 0 .1 5 9 0 .3 1
0 .2 0 0 0 .2 8 0 0 .1 3 0 0 .1 6 0 0 .1 4 2 0 .1 3 3 0 .1 3
0 .0 8 0 0 .0 7 0 0 .4 1 5 0 .1 2 7 0 .1 3 6 0 .0 2 6 0 .1 8 0
Table II. Data for Plotting Working Curve
L o t N o . C a d m iu m L e a d M a g n e s iu m Iro n A lu m in u m T in C o p p e r
2142 D u p lic a te i n t e n s ity r a tio s 0 .0 8 0 0 .0 7 0 0 .4 1 5 0 .1 2 7 0 .1 3 6 0 .0 2 6 0 .1 8 0
0 .0 7 8 0 .0 6 8 0 .3 9 3 0 .1 2 9 0 .1 3 6 0 .0 2 6 0 .1 8 0
A v . 0 .0 7 9 0 .0 6 9 0 .4 0 4 0 .1 2 8 0 .1 3 6 0 .0 2 6 0 .1 8 0
C h e m ic a l a n a ly s is , % 0 .0 0 0 9 7 0 .0 0 2 6 0 .0 7 1 0 .0 2 5 3 .3 0 T r a c e 0 .7 4 2200 D u p lic a te in t e n s i t y r a tio s 0 .2 9 0 0 .2 3 7 0 .2 2 0 0 .2 9 1 0 .1 8 1 0 .2 1 8 0 .7 5 0
0 .2 8 0 0 .2 3 7 0 .2 3 3 0 .2 7 6 0 .1 8 8 0 .2 1 0 0 .7 3 0
A v . 0 .2 8 5 0 .2 3 7 0 .2 2 6 0 .2 8 3 0 .1 8 5 0 .2 1 4 0 .7 4
C h e m ic a l a n a ly s is , % 0 .0 0 9 4 0 .0 1 5 7 0 .0 3 3 0 .0 4 6 4 .1 3 0 .0 1 0 3 3 .2 5 2201 D u p lic a te in t e n s i t y r a tio s 0 .1 1 8 0 .2 5 0 0 .2 4 8 0 .0 7 9 0 .2 1 5 0 .0 8 5 0 .6 4 0
0 .1 0 9 0 .2 4 5 0 .2 4 3 0 .0 8 5 0 .2 2 2 0 .0 8 0 0 .6 7 0
A v . 0 .1 1 4 0 .2 4 8 0 .2 4 6 0 .0 8 2 0 .2 1 9 0 .0 8 3 0 .6 6
C h e m ic a l a n a ly s is , % 0 .0 0 1 9 0 .0 1 7 2 0 .0 3 7 0 .0 1 8 4 .7 0 0 .0 0 2 2 2 .8 3
Table III. Comparison of Spectrographic and Chemical Analytical Results, Lot 2198
D u p lic a te i n t e n s i t y r a t io
S p e c tr o g r a p h ic , % C h e m ic a l, %
C a d m iu m L e a d M a g n e s iu m Iro n A lu m in u m T in C o p p e r
0 .1 4 5 0 .1 3 8 0 .2 3 5 0 .2 8 5 0 .1 8 0 0 .1 0 5 0 .7 2 4
0 . 1 5 0 0 . 140 0 .2 3 3 0 .3 0 0 0 .1 8 1 0 .1 0 0 0 .7 3 5
0 .1 4 8 0 .1 3 9 0 .2 3 4 0 .2 9 2 0 .1 8 1 0 .1 0 3 0 .7 3 0
0 .0 0 2 9 5 0 .0 0 7 2 2 0 .0 3 4 0 .0 4 7 4 .0 8 0 .0 0 3 1 2 3 .1 8
0 .0 0 2 8 0 0 .0 0 7 3 0 0 .0 3 2 0 .0 4 5 4 .1 3 0 .0 0 2 9 7 3 . 2 5
C O M P A R A T I V E A N A L Y S I S O F A Z IN C - B A S E A L L O Y B Y S P E C T R O - C H E M I C A L A N D C H E M I C A L M E T H O D S
T hree stan d ard sam ples covering the com positional range of Zam ak No. 2 an d w ith sufficient im purity variations were selected to establish working curves for th e spectrochem ical analysis of a fourth sam ple designated “ unknow n” . T he analyses of each of the th ree sta n d a rd samples, lots 2142, 2200, and 2201, are listed in T able II, w ith th e duplicate in ten sity ratios derived for th e respective elem ent spectral lines b y spark excitation of the three stan d ard s and one unknow n, all in duplicate. T he eight spectrogram s com prising this film were m ade as in daily routine procedure and no undue precautions were exercised in the execution of the step s of the analysis.
T he three sta n d a rd sam ples an d th e unknow n sam ple were very carefully analyzed in duplicate by two or more chemists, each of whom practiced precise and approved m et hods of chemical analysis, such as those sponsored by th e New Jersey Zinc Com
pany research laboratories. Large sam ples were employed for the analysis of low percentage im p u rity elem ents lead, tin, and cadm ium , an d for these elem ents more th an one m ethod of analysis was used.
T able I presents ty p ical spectrochem ical d a ta derived from the spark excitation of No. 2142, one of th e stan d ard sam ples. Table II lists th e individual average elem ent intensity ratio s and the corresponding chem ical com positions for each stan d ard sam ple used in th is analysis. T h e w orking curves shown in Figure 3 were derived from p lo ttin g th e values in T able II. An interesting and gratifying featu re of th e working curves is th e accuracy w ith which all points fall on stra ig h t lines. T able I I I presents th e results of th e analysis on th e unknow n lot 2198 by spectrochem ical and chemical m ethods.
A consideration of th e average arithm etical per cent error in determ inations of th e various elem ents reveals th a t the m ajor constituents, copper and alum inum , were m easured well w ithin an error of 3 % of th e am o u n t present. T he error expressed as Per cent deviation from th e chemical value of each elem ent is:
magnesium 6.2% , cadm ium 5.3% , tin 5.0% , iron 4.4% , copper 2-1%, alum inum 1.2% , and lead 1.0%. T h e 6.2% deviation for m agnesium m ight a t first glance ap p ear high enough to invalidate th e w orth of th is determ ination. However, when the figure 6.2 % is arithm etically applied to th e accepted value of
0.032% we o b tain a difference of 0.00198%, which, if equaled in routine chem ical analyses, would be considered satisfac
tory. T h e accuracy of the cadm ium evaluation could, of course, be helped m aterially by th e use of. a calibration curve constructed from tra n s
mission results taken in th a t region of th e spectrum . T he yardstick phrase “m easuring an elem ent w ithin an error of 3 to 5% of th e am o u n t pres
e n t” loses som e of its com
p arativ e signification when a p plied to an elem ent such as tin, which, in th e case under consideration, is p resent in the am o u n t of oidy 0.00297%.
We can, t h e r e f o r e , a c c e p t higher values th a n 5% when we seek to evaluate elem ents present in a concentration on th e order of 0.003% , since in the case of th e tin evalua
tion in th is analysis 5 % of 0.00297% is 0 .0 0 0 1 4 8 % , a negligible q u a n tity in routine control analysis. A decrease in th e accuracy of analysis a t low concentrations is to be expected, particularly a t levels w here th e difference between line w ith un
derlying background intensity and background intensity is sm all com pared to background.
A N A L Y S I S T IM E R E Q U IR E M E N T S
Sam ple procurem ent and sam ple preparation are in m any spectrochem ical m ethods g reat eohsum eis of tim e. T he flat disk technique simplifies sam ple procurem ent and, since no chemical tre a tm e n t is necessary in sam ple preparation (only simple la th e machining), very rap id tre a tm e n t is possible.
An analysis tim e of 5 to 7 m in u tes p er elem ent is easily achieved for a single sam ple; under norm al routine conditions an analysis tim e of 2 m inutes per elem ent is achieved for a full film of seven unknow n sam ples and one sta n d a rd sam ple. Seven elem ents, of course, arc evaluated for bo th th e full film containing seven spectrogram s an d th e film w ith only one spectrogram .
If one were to d o u b le these routine spectrochem ical production tim e intervals of analysis per elem ent, a com parison w ith tim e requirem ents for th e chemical analysis of certain elem ents would still be m eaningless; one cannot com pare 30 m inutes to 12 hours, which are th e tim e requirem ents for determ ining cadm ium . T he 30-m inute figure can be used for th e spectrochem ical evaluation of cadm ium only if all film processing tim e is charged against one determ ination; 12 hours is a charitable tim e interval for a precise chemical cadm ium determ ination by approved m ethods for th e N o. 2 Z am ak alloy.
Iron, copper, and lead can be rapidly analyzed by chemical an d electrolytic m ethods. Alum inum , m agnesium , cadmium, and tin are the difficult tim e-consum ing chemical determ inations.
W hen th e analytical problem is placed on a volum e basis where m any sam ples are handled each d ay for complete analyses, the spectrochem ical m ethod, as se t forth in th is paper, gains in attractiv en ess from th e tim e-requirom ent standpoint.
A C C U M U L A T E D D A T A F R O M L A B O R A T O R Y C O N T R O L W O R K
I t is sta n d a rd practice in th is laboratory to assemble d ay to d ay analytical d a ta on prospective stan d ard s before placing them
