INDUSTRIAL AND ENGINEERING CHEMISTRY
ANALYTIC AL E D IT IO N
H A R R IS O N E. HOWE, E D IT O R • ISSUED M A R C H 15, 1941 » VO L. 13, NO . 3 • C O N S E C U T IV E NO. 6
D e t e r m i n a t i o n a n d S e p a r a t i o n o f P o t a s s i u m a s P e r io d a t e . ♦ Hobart H. W illard an d A lbert J. B oyle 137
R e c o v e r y o f A s p h a l t s a n d L iq u id A s p h a lt ic R o a d M a t e r ia ls f r o m S o l u t i o n ...
T. F. Ford a n d K. G . A rabian 140
P h y s i c o c h e m i c a l A s s a y o f V i t a m i n A ...
Norris D ean Em bree 144
D e t e r m i n a t i o n o f S m a l l A m o u n t s o f Z in c i n P la n t M a t e r i a l s ... H ale C o w lin g and E. J. Miller 145
D e t e r m i n a t i o n o f T o t a l V i t a m i n A C o n t e n t o f D a ir y B u t t e r s ... ....
R. H. N eal, C . H. H aurand, an d F. H. Luckm ann 150
T e s t F o r m u l a s f o r R e c l a i m e d R u b b e r ...
H en ry F. P alm er a n d R obert H. C rossiey 154
C h e m i c a l C o n s t i t u e n t s o f C o t t o n s e e d H u l l s . . . . M an n in g A . Sm ith a n d C . B. Purves 157
D e t e r m i n a t i o n o f P r o p o r t i o n o f d - a n d / - I s o m e r s in S a m p l e s o f L a c t i c A c i d ... ....
Stanford M oore, Robert J. D im ler, an d Karl Paul Link 160
F a s t n e s s t o A t m o s p h e r i c G a s e s o f D y e s o n C e llu lo s e A c e t a t e R a y o n ...163
R a p id a n d A c c u r a t e D e t e r m i n a t i o n o f C a d m iu m . T. L. Thom pson 164
D e t e c t i o n o f S o d i u m A l g i n a t e i n D a ir y P r o d u c t s
C h a rles W . S ch ro ed er an d P h ilea s A . R acicot 165
D e t e r m i n a t i o n o f M e n t h o l i n O il o f P e p p e r m i n t
Thom as W . B rignall 166
M e t h o d s f o r E s t i m a t i o n o f S o m e A m i n o A c id s i n C o m G r a i n ...D. M. Doty 169
N e w I n s t r u m e n t f o r R h e o l o g i c a l S t u d i e s o f P la s t ic S u b s t a n c e s . * ... C . R. B a iley 173
M e a s u r e m e n t o f F lo w P r o p e r t ie s w i t h G a r d n e r M o b i l o m e t e r ... P aul W . K inney 178
D e t e r m i n a t i o n o f B lo o d M a g n e s i u m ...
F ran ces W . Lamb 185
D e t e r m i n a t i o n o f A m m o n i a c a l a n d N i t r a t e N i t r o g e n i n D e c o m p o s e d P la n t M a t e r ia l . J. G . ¿h rik h a n d e 187
M a c h in e a n d M e t h o d s fo r T e s t i n g M e c h a n i c a l S t a b i l i t y o f L a t e x . ... ...
C h as. K. N ovotny, an d W ilb u r F. Jordan 189
S i l i c a a n d P y r e x G la s s S t i l l s w i t h A u t o m a t i c C o n s t a n t - P r e s s u r e F e e d s . C . S. P iper an d A . C . O ertel 191
G e lo m e t e r fo r S t a r c h P a s t e s ... ....
R. M. H ixon an d B ern a d in e Brim hall 193
I m p r o v e d T h i x o t r o m e t e r ...R. W . K ew ish 195
M I C R O C H E M I S T R Y
A p p lic a t io n o f G r a t i n g M ic r o s p e c t r o g r a p h t o P r o b le m o f I d e n t i f y i n g O r g a n ic C o m p o u n d s
Edwin E. Jelley 196
E le c t r ic H e a t i n g M o r t a r fo r U s e i n C a r b o n a n d H y d r o g e n M i c r o c o m b u s t i o n s ... ....
G . Frederick Smith an d W m . H. Taylor 2 0 3
V o l u m e t r i c F la s k s f o r M i c r o a n a l y s i s ...
Earle R. C a le y 2 0 4
M O D E R N L A B O R A T O R I E S
N e w S c i e n c e B u i l d i n g a t K a n s a s S t a t e C o lle g e . . G . N athan R eed 2 0 5
T h e A m e ric a n C h e m ic a l S o c ie ty ass u m e s n o r e s p o n s ib ility fo r th e s ta te m e n ts a n d o p in io n s a d v a n c e d b y c o n tr ib u to r s to i t s p u b lic a tio n s . 2 5 ,3 0 0 co p ies of th is issu e p r in te d . C o p y r ig h t 1941 b y A m e ric a n C h e m ic a l S o c ie ty .
P u b l i c a t i o n O fB ce:
E d i t o r i a l O ffices R o o m 706, M ill* B u i l d i n g , W a s h i n g t o n , I ) . C . T e le p h o n e s N a t i o n a l 0 8 48. C a b l e : J i e c h e m ( W a s h i n g to n )
P u b lis h e d b y th e A m e ric a n C h e m ic a l S o c ie ty , P u b lic a tio n OfBce, 2 0 th &
N o r th a m p to n S ts ., E a s to n , P e n n a . E n t e r e d a s seco n d -class m a tte r a t th e i o s t Office a t E a s to n , P e n n a ., u n d e r th e A c t of M a r c h 3 , 1879, a s 24 tim e s a y e a r . I n d u s tr ia l E d itio n m o n th ly o n th e 1 st; A n a ly tic a l E d itio n m o n th ly o n th e 1 5 th . A c c e p ta n c e fo r m a ilin g a t s p ecial r a t e of p o s ta g e p ro v id e d for m S e c tio n 1103, A c t of O c to b e r 3 , 1917, a u th o r iz e d J u ly 13, 1918.
A n n u a l s u b s c rip tio n r a te , In d u s t r i a l Ed i t i o n a n d An a l y t i c a l Ed i t i o n
so ld o n ly as a u n it , m e m b e rs S3.00, o th e r s $4.00. F o re ig n p o s ta g e to c o u n trie s n o t in th e P a n A m e ric a n U n io n , $ 2 .2 5 ; C a n a d ia n p o sta g e . $0.75.
E a s t o n , P e n n a .
A d v e r ti s i n g D e p a r t m e n t : 332 W e s t 4 2 n d S t r e e t , N e w Y o r k , N . Y . T e le p h o n e s B r y a n t 9-4430
S in g le copies: I n d u s tr ia l E d itio n , $ 0 .7 5 ; A n a ly tic a l E d itio n , $0-50. S p ecial r a te s to m e m b ers.
N o claim s c a n b e allo w ed f o r co p ies of jo u r n a ls lo s t in th e m a ils u n less s u c h c la im s a r e re c e iv e d w ith in 00 d a y s of th e d a t e of issu e, a n d n o claim s w ill b e allo w ed fo r issu es lo s t a s a r e s u lt o f in su ffic ien t n o tic e o f c h a n g e of ad d re s s . (T e n d a y s ' a d v a n c e n o tic e re q u ire d .) " M is s in g fro m files"
c a n n o t b e a c c e p te d a s th e re a s o n fo r h o n o rin g a claim . A d d re s s c la im s to C h a rle s L . P a rs o n s , B u sin ess M a n a g e r, M ills B u ild in g , W a s h in g to n , D . C ..
U . S . A.
4 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 V ol. 13, N o. 3
“Safeguards to the Nation’s Health”
S E T T I N G T H E P A C E I N C H E M I C A L P U R I T Y S I N C E 1 8 8 2
,
T | 7 f
B a k e r & A d a m s o n
D i v i s i o n of G E N E R A L C H E M I C A L C O M P A N Y , 4 0 R e c t o r St., N e w Yor k C .T ? A c & /s S a le s O ffi c e s : A tla n ta • B a ltim o r e • B o sto n • B u ffalo • C h a r lo tte ( N . C .) • C h ic a g o • C le v ela n d * D e n v e r • D e tr o it H o u sto n • K a n s a s C ity • M ilw a u k e e * M in n e a p o lis • N e w a r k ( N . J . ) • N ow Y o rk • P h ila d e lp h ia • P itt s b u r g h
P ro v id e n c e (R . I . ) • S t. L o u is • U tic a ( N . Y .) P a c ific C o a st S a le s O ffi c e s : S a n F r a n c is c o • L o s A n g ele s P a c ific N o r th w e s t S a le s O f f i c e s : W e n a tc h e e ( W a s h .) • Y a k im a ( W a s h .)
---I n C a n a d a : T h e N ic h o ls C h e m ic a l C o m p a n y , L im ite d • M o n tre a l • T o r o n to • V a n c o u v e r ---
Tew quantitative analyses require such a high degree o f purity in reagent chem icals as that demanded for lead, arsenic and fluorine determinations in food products.
The minute quantities o f these elements w hich m ay e v e n tu a lly be d eterm in ed make it im perative that particular care be exercised by the chemist in the choice o f his reagent chem icals.
B a k e r & A d am so n R e a g e n ts a r e f u l ly qualified for food an alyses; they are made to meet the most exacting requirements.
A ll o f them offer the low m axim um lim its of impurities which are essential in this work.
G et a c q u a in te d w ith th ose B a k e r &
A d am so n R e a g e n ts reco m m en d ed fo r lead, arsenic and fluorine determinations
— and you w ill soon consider only Baker
& Adam son Reagents for a ll you r work.
M arch 15, 1941 A N A L Y T I C A L E D I T I O N 5
C o r n i n g
y means i l Hesearrh in (ilass
“ P Y R E X ” is a registered tr a d e -m a r k a n d iiulicales m a n u fa c tu r e b y
C O R N I N G G L A S S W O R K S . C O R N I N G , N* Y . A gain Corning brings to the laboratory new
features of convenience and economy by developing a m ethod of tool finishing “ P Y R E X ” B rand Ring Neck Flasks, (Catalog Nos. 4180, 4200, 4220 and 4260).
Tooling insures accuracy of inside dimensions a t the m outh of the neck—accuracy of stopper fit. N o longer do you have to fit stoppers by trial and error.
Com ing’s m ethod of fabrication gives greater me
chanical strength, for th e ring and neck are now con
tinuous—all o f the one original mass. Y ou’ll get less chipping, too— the top is fire-polished.
M anufacture of tooled neck flasks affording accurate stopper fit in sizes up to and including 6000 ml has now been standardized a t no increase in price. T his feature will be adapted to larger sizes as m anufacturing facili
ties permit, b u t for a tim e it m ay be necessary to supply flasks of th e old style, particularly in the larger sizes.
This improved neck finish is another reason why you should specify flasks made from “ P Y R E X ” brand Chemical Glass—the Balanced Glass.
T h e Indicator is completely portable, and overcomes a common difficulty of glass-electrode instrum ents in th a t it may be used when relative hum idity is as high as 9 5 % .
A lab helper can learn prom ptly the routine operation of the instrum ent, since it is handled in the same general fashion as a portable potentiom eter tem perature indicator.
Com plete directions accompany the instrum ent. F or fu rth e r facts, see C atalog E-96 ( 1 ) .
Jrl A d E . \ 0 6 0 0 B (S )
T h e p olarizin g cell and electrode are strong, sim ple and easy to use. There is no h ighly sensitive galvanom eter. A nd the m eas
urement is recorded a u to m a tic a lly by a M icrom ax Recorder. Its record is in ink, is easy to read, and saves the time usually re
quired for recording o f instrument readings, l ’reso n t u s e rs in c lu d e :
A m erican C y an a m id Co.
U n iv . o f C in c in n a ti E a stm a n K odak Co.
E . I. d u P o n t d e X e m o u rs
& Co.
1-os A ngeles Police D ept, M em o rial H o sp ital, N . Y.
S tep h a n o B ro th e rs
W e ste rn E le c tric C o.
B ry n M aw r C ollege U n iv . o f D elaw are H a rs h a w C hem ical Co.
M erck & Co.
H a r v a r d U n iv . M ich ig an S ta te U n iv . T e x a s Co.
L EEDS Ä. N O RT H R U P C O M P A N Y , 4920 STENTON AVE., PH I LA., PA.
LEEDS & N O R TH R U P
AIITAHATir rAMTDńl g M r A T . T P F A T I W P . r t l R N Ä C F « ?
Metal Analyses Are Speeded Up 6 Times
It used to take chem ists 8 hours to analyze the 150 sam ples that come to a certain m etal
lurgical lab every day. N ow , the sam e men do their work in one-sixth the time, w ith their new Knorr- A lbers Recording M icrophotometer, T h is instrument is built by L&N according to the K ettering Foundation researches of Pro
fessors Knorr and Albers of A ntioch College, and is easily capable o f b eing operated w ithin the tolerances o f chem ical methods.
T h e equipment succeeds because it uses spectrograms w ith a modern, non-photo
graphic method of recording. It consists of 2 units. One “scans” the spectogram by pass
in g a beam o f light through it onto a photocell. T h e other unit is a standard Speedomax high-speed recorder w hich records in ink the v a ry in g current o f the cell— hence the spectrum -line densities o f the spectrogram.
Spectrum-line densities o f standard and test plates are recorded on the same chart.
Lines hardly visib le w hen projected may be measured quite accurately. A line may be m easured in different exposures or in differ
ent steps o f a sector exposure. . . . T h is in
strument is a tool for either research or routine work. If you’d like further inform ation, w e ’ll gla d ly send it.
D ropping-H g Electrode Is C onveniently A pplied
In E lectro-C hem ograph
Solutions For Oil Filters
Studied with L&N pH Indicator
Chemists who are thinking o f using the Hey- rovsky dropping-m ercurv-electrode method of analysis w ill find several advan tages in the L&N Electro-Chem ograph as the equipment for the purpose.
P roduction of oil filters by the F ram Corp., Rum fprd, R. 1., is an activity in which the pH of a process solution is im portant. T h e filters are alkali-im pregnated, to neutralize acidity in automobile-engine oil. and Fram uses pH m easurem ents freely in preparing the filter-im pregnating solutions. A nd one of the principal rea
sons pH measurem ents are so easy to make iti this plant is th at the m easuring instru
m ent is an L& N U niveral pH Indicator, w ith glass electrodes.
T h is Indicator reads directly in p H — no voltage to co nvert; no tem perature- correction to compute. Its sm all, rugged electrodes are m ounted in the instrum ent case, directly above the sample-holder. T h e sample may be as small as 5 ml.
M arch 15, 1941 A N A L Y T I C A L E D I T I O N 7
The Avoi rdupoi s Pound which served a s the ex chequer s ta nd
ar d o f mas s during the d a y s o f Queen Elizabeth.
Standard of M ass. . .
Since th e very beginnings of recorded history, standards of mass have been established for th e control of accuracy an d uniform ity in weighing.
Today, pre-determ ined stan dard s of p u rity control th e accuracy and uniform ity of M al
linckrodt A. R. Chemicals. Stringent refining,
testing and re-testing by skilled chem ists insure dependable analytical chemicals for accurate analysis.
S end for la ste st M allin ck rod t catalogu e o f A n a ly tic a l R ea g en ts an d oth er ch em icals for lab oratory use.
I t con tain s d etailed d escrip tion s o f ch em icals for ev ery ty p e o f a n a ly tica l w ork . . . gravim etric, gaso- m etric, calorim etric or titrim etric.
M A L L I N C K R O D T C H E M I C A L W O R K S
ST. LOUIS • PHILADELPHIA • M ONTREAL
CH ICA G O • NEW YORK • TORONTO
8 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 V ol. 13, No. 3
P ro tectio n
- %
<••' •sïA>;-v »»
ARE Y O U EQUI PPED TO SEE THE DI FFERENCE?
• R utile and anatase, tw o im portant oxides o f T iO z, have identical chemical form ulae, yet each has a radically different behavior from th e other. T heir wide-spread use in processes w hich m ust adhere to "stepped u p ” pro d u ctio n schedules m ake it im perative that titanium bearing ores and refined oxides b e analyzed by a rapid, accurate m ethod.
Such a m ethod is available w ith th e G-E X R D U nit.
T itanium oxides w hen analyzed by x-ray diffraction may reveal three types o f patterns: P attern (A) was produced by pure rutile; Pattern (B) was registered by pure anatase. A m ixture o f the tw o w ill result in P attern (C), and th e d en sity o f each pattern w ill give a quantitative indication o f the am ounts o f each oxide present.
From such easy-to-obtain, illustrated data, it is possible to establish com plete control o f th e oxide m ixtures and pre
vent failure o f m anufacturing processes. F or com plete inform ation about th e G -E X R D U n it and its application to your problem s, address your request to D epartm ent R33-
GENERAL ELECTRIC X-RAY CORPORATION
2 0 1 2 J A C K S O N B L V D . C H IC A G O , IL L ., U . S . A .
M arch 15, 1941 A N A L Y T I C A L E D I T I O N 9
TYPICAL <=> ITEMS
C a t. N o . 1 8 0 0 3
KIMBLE MODERN H LIEBIG CO N D EN SERS
I With Plai n I n n e r Tube ma de of Kimble
U Resistant Glass
L e n g th o f J a c k e t
m m .
Q u a n t it y in C a s *
O t h e r s t y l e s o f i n n e r l u b e s c a n b e o b t a i n e d . F o r q u a n t i t y p r i c e s , s e e y o u r d e a l e r .
D C A L I B R Â T Ï 0 *
...;
10 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. 13, N o. 3
A . H . T . CO. S P E C I F I C A T I O N
AIR DRIVEN S T IR R IN G APPARATUS
A n e w m o d e l , of s i m p l e d es i gn a n d h ig h t o r q u e , e s p e c i a l l y a t low speeds
•at-
A
9 224.
S T IR R IN G A P P A R A T U S, A IR D R IV E N , A .H .T . CO. S p ecification . A new m odel w ith p is to n d riv e , fo r o p e ra tio n a t v a ria b le sp e e d s b y m e a n s of co m p re sse d a ir o r v a c u u m . O p e ra te s on p re ssu re s as low a s 2 lb s. R e c o m m e n d ed p a r tic u la r ly fo r u se in la b o ra to rie s w h ere v o la tile liq u id s o r ex p lo siv e v a p o rs m a k e h a z a rd o u s th e u se of m a n y e le c tric s tirre rs .
T T h e p isto n d riv e s a s tu r d y m a c h in e d flyw heel, S j^ -in c h e s d ia m e te r, a n d a t ta c h e d s tir r e r sh a ft. A ir u n d e r p o sitiv e o r n e g a tiv e p re ssu re re a c h e s th e p isto n c h a m b e r th r o u g h a hollow tu b e 3 in ch es long X % -in c h d ia m e te r b y w hich th e a p p a r a tu s c a n b e a t ta c h e d to o rd in a ry s u p p o rt sta n d s.
lia ch stirrer is supplied w ith an ad ju sta b le ch u ck to fit m eta l or g la ss rods J^-incli d ia m e ter, and, if desired , w ith M onel m eta l stirring rod 9 inches lon g w ith propeller 1 ' ^-inches d iam eter, or w ith rod s 12 or 18 in ch es lon g, w ith propeller 2-inches diam eter. Stirrers w ith 12 and 18-inch rods are p ro v id ed w ith an a u x ilia ry b ea rin g o f S ta in less s te e l located 7 in ch es below' th e ch u ck and su sp en d ed on a S ta in less s te e l rod J^-inch d iam eter. T h is a lig n in g a rrangem ent elim in a tes " w h ip ” and insures sa tisfa cto ry op eration in deep con tainers.
M a x im u m speed, w ith o u t load , a t 15 lb s. air pressure is a p p ro x im a tely 2500 r .p .m ., w h ich ca n b e red u ced b y ch a n g in g th e pressure a t th e source. R eq u ires a p p ro x im a tely 1.3 cu . ft. o f com p ressed air per m in u te a t a b o v e speed. W ill m ix 4 liters o f A lu m in u m H y d ro x id e 10% so lu tio n th o r o u g h ly in a 4 lite r b eak er u sin g 15 lb s. air pressure or v a cu u m eq u iv a len t t o 15-inch colu m n of m ercu ry, ex cep t w h en u sin g th e 9 -in c h stirrin g rod w ith 1!A - inch propeller w h ich w ill m ix su ch so lu tio n s c o m p le te ly o n ly w h en u sin g com p ressed air.
N o . 9 2 4 2 -D S u p port w ith h e a v y sem i-circu lar base sh a p ed to fit around cy lin d rica l v essels up to 12-inch d iam eter, an d w ith c a d m iu m p la te d ste e l rod 3 0 in ch es lon g X ? i-in c h diam eter, is recom m en d ed for u se w ith 12 or 18-inch stirrin g rods. T h is su p p ort p ro v id es greater sta b ility a n d therefore quieter o p era tio n th a n th e u su al su p p o rt w ith rectan gu lar or trip od base.
N o . 9 2 4 5 G lass Stirring R o d s, 2 5 0 m m lo n g X G-mm diam eter, can a lso be used w ith th is stirrin g ap p aratu s. R u b b er tu b in g w ith J^-inch bore can be used t o co n n ect th e Stirrer to pressure or v a cu u m source.
9224. Stirring Apparatus, Air D riv en , A .H .T . Co. S p ecifica tio n , a s ab o v e described, w ith stirrin g rod of M o n el m eta l, 9 in ch es lon g w ith p ro
p eller l ji-in c h c s diam eter, b ut w ith o u t s u p p o r t... 9.25 C ode W o r d ... Oiheg 9224-A . D itto , w ith a d ju sta b le ch u ck b u t w ith o u t stirrin g rod or su p
p o r t...: ... 7.75 C ode W o r d ... Oihfe Stirring A sse m b ly , Air D riven , A .H .T . Co. S p ecification , sim ilar to
92 2 4 b ut for u se in d eep er b a th s or larger b o ttles. W ith au xiliary b earin g o f S ta in less ste e l and w ith longer 92 4 6 M o n el m eta l stirring rod w ith four-blade propeller 2-in ch es d iam eter. C om p lete w ith 9 2 4 2 -D S u p port w ith h e a v y sem i-circular base w h ich a c co m m o d a tes v e s se ls 12-inches d ia m e ter and cad m ium plated ste e l rod 30 inches lo n g X M -inch d iam eter, and w ith 3214 C lam p holder. % - inch, b ut w ith o u t glass ja r sh o w n in illu stration .
L e n g th o f stirrin g rod, in c h e s .. . . ... 12 18 D ia m e te r o f propeller, in c h e s ... 2 2 9 226.
E a c h ... 17.75 C ode W o rd ... Oihha
18.25 O ih iv 9227. D itto , w ith M o n e l m e ta l stirrin g rod b ut w ith o u t su p p ort, cla m p
h old er, or glass jar.
L e n g th of stirrin g rod, in c h e s... 12 18 E a c h ... 13.00
C ode W o r d ... Oilimq 13.50 Oihol
10% d isc o u n t in lo ts o f 12, No. 9224 to 9227 assorted
9226.AR TH U R H. T H O M A S C O M P A N Y
R E T A I L — W H O L E S A L E — E X P O R T
LA B O R A TO R Y APPA R A TU S A N D REAG ENTS
W EST W A S H I N G T O N SQUARE, P H I L A D E L P H I A , U. S. A.
C a b le A ddress, “ B a la n c e ” P h ila d e lp h ia
INDUSTRIAL a n d ENGINEERING CHEMISTRY
A N A L Y T I C A L E D I T I O N
P U B L I S H E D B Y T H E A M E R I C A N C H E M I C A L S O C I E T Y • H A R R I S O N E. H O W E , E D I T O R
Determination and Separation of Potassium as Periodate
H O B A R T H . W IL L A R D a . n d A L B E R T J . B O Y L E 1 U n iv e r s it y o f M i c h i g a n , A n n A r b o r , M ic h .
T
H E determ ination of potassium as periodate, K I 0 4, offers a num ber of advantages. I t has a high molecular weight, and can be determined volumetrically by a very exact titration. I t is only sparingly soluble, a saturated solution a t 25° C. being 0.022 molar (2). I t contains about the same percentage of potassium as the chloroplatinate and cobalti- nitrite and much less than the perchlorate.The first experiments along this line were made by G reat
house (1), who added periodic acid to the solution, 2 or 3 ml.
in volume, and completed the precipitation by adding alcohol, free from aldehyde. He carried out a few gravim etric and volu
metric determ inations, th e results being usually slightly low, b u t did very little on the separation of potassium from other metals. A t th a t tim e the price of iodine was high, and the preparation of periodic acid was an expensive process. Since th a t time two satisfactory' m ethods for preparing the acid have been published and the reagent has become less expen
sive. As the reagent is now available, it seemed desirable to make an extensive investigation of this m ethod of determining and separating potassium, and in particular, to find a better solvent than ethyl alcohol which is so easily oxidized th a t it is alm ost impossible to avoid some reduction of periodic acid to iodic acid.
The reaction used in titratin g periodate to iodate was first suggested by M uller and Friedberger (3):
1 0 ," + 2 1 - = I O r + I 5
and is quantitative only in a neutral solution buffered by carbonic acid-bicarbonate or boric acid-borate, preferably th e latter. T he free iodine is then titra te d by standard ar- senite. This m ethod has th e advantage th a t iodate does not interfere, as it would if the periodate were reduced to iodide.
In the la tte r process, however, th e equivalent would be much smaller—one eighth of the molecular weight.
The periodate m ethod for potassium is both rapid and accurate, and can be applied to am ounts of potassium as low as 0.4 mg.
E x p e r im e n ta l
S e l e c t i o n o f a S o l v e n t . As indicated above, th e selec
tion of the proper solvent is a m a tte r of prime importance.
I t m ust possess the following properties: (1) I t m ust n o t be appreciably oxidized by periodic acid during the tim e re-
1 P r e s e n t a d d re s s , W a y n e U n iv e r s ity , D e tr o it, M ic h .
quired for the analysis, 0 .5 to 2 hours. (2) I t should be miscible w ith w ater a t least to the extent of about 10 per cent of th e latter by volume. (3) Potassium periodate m ust be insoluble in the solvent and yet it m ust dissolve sodium periodate and such other salts as m ight be present.
As explained above, Greathouse (1) used ethyl alcohol, free from aldehyde, since the aldehyde is more easily oxidized than the alcohol. This, however, was not an ideal solvent because some oxidation of the alcohol invariably occurred.
Among the solvents which are less affected by oxidizing agents is tertiary butyl alcohol; this was therefore first investigated.
I t was found, however, to dissolve so little sodium periodate as to be useless for the purpose. Admixture of ethyl acetate did not improve m atters. O ther solvents tried in which sodium periodate was insoluble were dioxane, the earbitols, Cellosolve, and diethylene glycol.
I t was found th a t if ethyl acetate was added to ethyl alcohol, the resistance of th e la tte r to oxidation was con
siderably increased, whereas its solvent power was not diminished.
A q u a n tity o f 95 per c en t e th y l a lco h o l, free from a ld eh y d e, w as prepared b y refluxing th e a lco h o l for 2 or 3 hours a fte r th e a d d itio n o f 0 .5 gram o f so d iu m h yd ro x id e an d 2 .5 gram s o f silv e r n itr a te per liter. T h e a lcoh ol w a s th e n d istille d a n d m ix ed w ith a n eq u al v o lu m e o f a n h y d ro u s e th y l a c e ta te . T h e m ix tu re w a s m iscib lo w ith th e q u a n titie s o f w a ter w h ich w ere required and sh o w ed considerable resista n ce to o x id a tio n b y p eriod ic a cid . O ne gram o f p eriod ic a cid d isso lv ed in 100 m l. o f th e so lv e n t sh o w e d th e first tra ces o f free io d in e a fte r sta n d in g a t room tem p er a tu re for 24 hours. S in ce in m o s t ca ses t h e tim e required for th e separa
tio n o f p otassiu m w a s from 15 m in u te s to 1 hour, it is ap p a ren t th a t o n ly v e r y s lig h t o x id a tio n o f th e organ ic s o lv e n t cou ld occur.
T h e m a g n itu d e o f th is effe ct is sh ow n b y th e fa c t t h a t th e average o f a lon g series o f g ra v im etr ic d ete r m in a tio n s (o n ly p art o f w h ich are recorded in th is p ap er) sh ow ed an error o f + 0 . 0 2 m g ., an d th e v o lu m e tric d e term in a tio n s —0.0 5 m g. T h is w o u ld in d ic a te th a t th e p recip ita tes c o n ta in e d a tra ce o f io d a te o w in g to v ery s lig h t red u ction b y th e so lv e n t, b eca u se th e p ercen ta g e o f p o tassiu m in th e io d a te is o n ly s lig h tly less th a n in th e p eriod ate, w h ereas th e io d a te is n o t d eterm in ed a t all in th e v o lu m e tric p rocess. T h e se resu lts are m u c h b e tte r th a n th o se o b ta in ed b y G reath ou se ( / ) . I t w a s also found p o ssib le to reduce c o n sid er a b ly th e con cen tration o f periodic acid .
P r e p a r a t i o n o p R e a g e n t s . The periodic acid used was recrystallized from conccntrated nitric acid until free from iodic acid. Some of it was prepared by the electrolytic process (5) and although originally free from iodic acid, some batches were found to contain a good deal of the la tte r 137
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. 13, No. 3 after standing for a m onth or two. This is probably due to
the catalytic effect of traces of colloidal platinum derived from the electrodes. A solution of periodic acid to which considerable colloidal platinum is added evolves oxygen rapidly. The acid prepared by the chemical process (4) is always entirely stable. Small am ounts of iodate are easily detected as follows:
O n e-half gram o f th e periodic acid is d isso lv ed in 25 nil. o f w a ter, a few drops o f 0 .2 5 M silv er n itr a te are a d d ed , an d the so lu tio n is w arm ed u n til t h e y ello w ish -b ro w n silv er p eriod ate d isso lv es, w h ich sh o u ld occu r read ily a t a b o u t 8 0 ° C. I f io d ic acid is p resen t, a w h ite floccu len t p recip ita te o f silv er io d a te w ill form . If th e brow n silv e r p eriod ate is n o t c o m p le te ly d isso lv ed by h ea tin g , a drop or tw o o f n itric a cid , free from n itro u s acid, sh ou ld be ad d ed .
The potassium and sodium periodates used were purified by recrystallization and tested for iodate by the method of Willard and Thompson (6). This is similar to th e method suggested above, except th a t most of the periodate in the sample to be tested is first removed by the addition of an ex
cess of potassium nitrate, after which the solution is acidified with nitric acid and tested for iodate by the addition of silver nitrate. In this way it is possible to detect 0.03 per cent of iodate in periodate.
The potassium nitrate used in this work had been carefully purified and dried a t 105° to 110° C. for several hours. An attem p t was made to fuse th e salt a t about 300° C., b u t the resulting material contained considerable nitrite.
138
T a b l e I. De t e r m i n a t i o n o f Po t a s s i u m a s Pe r i o d a t e i n Pr e s e n c e a n d Ab s e n c e o f So d i u m
W t. of K N a A d d ed W t. of E r r o r in K
as N itr a te a s N itr a te K IO « G r a v im e tr ic V o lu m e tric
G ram M g. G ram M g . M g .
0 .0 7 9 4 0 .4 6 7 6 +0 .1
0 .0 4 9 0 0 .2 8 8 7 + 0 .1 0 .0
0 .0 4 0 5 0 .2 3 9 1 +0 .1 + 0 .1
0 .0 3 8 2 a 0 .2 2 4 1 - 0 . 1 - 0 . 1
0 .0 3 0 7 0 .1 8 0 9 0 . 0 - 0 . 1
0 .0 2 2 4 0 .1 3 1 3 - 0 . 1
0 .0 0 3 0 0 .0 1 7 1 - 0 . 1 - ô . ’ i
0 .0 6 0 0 ‘¿8 0 .3 5 2 4 - 0 . 1 0.0
0 .0 4 2 8 73 0 .2 5 1 8 0 . 0 0.0
0 .0 4 6 4 135 0 .2 7 4 6 + 0 .3 +0 .3
0 .0 4 2 0 135 0 .2 5 1 7 + 0 . 8 +0.6
0 .0 4 8 1 ° 140 0 .2 8 4 2 + 0 . 2 +0.2
0 .0 4 0 7 o 143 0 .2 4 0 6 + 0 .2 +0 .1
0 .0 4 4 0 a 190 0 .2 5 9 8 + 0 .2 -0 .1
0 .0 3 3 5 a 190 0 .1 9 8 0 + 0 .1 0.0
0 .0 0 1 7 54 0 .0 0 9 8 0 . 0
0 .0 0 1 3 54 0 .0 0 7 7 0 .0 - Ô/2
0 .0 0 0 7 54 0 .0 0 4 1 0 . 0 0.0
5 m l. of w a te r used
0 .0 0 0 8 ,0 .0 0 4 5 0 .0 +0.2
0 .0 0 0 8 0 .0 0 4 3 - 0 . 1 0.0
0 .0 0 0 8 27 0 .0 0 4 5 0 . 0 0.0
0 .0 0 0 8 27 0 .0 0 5 2 + 0 .1 +0 .1
0 .0 0 0 4 27 0 .0 0 2 5 0 . 0 - 0 .1
0 .0 0 0 4 27 0 .0 0 2 0 - 0 . 1 - 0 . 1
« 180 m l. of a lc o k o l-a c e ta te m ix tu re u sed .
G e n e r a l P r o c e d u r e
A sa m p le w eig h in g 0.1 t o 0 .2 gram is d isso lv ed in w a ter in a 150-m l, b eaker. I f p o ta ssiu m ch lorid e is u sed it m u st b e ev a p o rated t o d ryn ess w ith 10 m l. o f co n cen tra ted n itric a cid ; other
w ise th e ch lorid e w ill ca u se red u ction o f p eriod ic a cid . T o th e n itr a te d isso lv ed in 4 to 5 m l. o f w a te r 3 m l. o f w a ter co n ta in in g 1 gram o f p eriod ic acid are a d d ed , th e m ix tu re is stirred, an d 3 or 4 m in u te s are allow ed for th e p o ta ssiu m p eriod ate t o p recip ita te.
N in e ty m illiliters o f th e a lc o h o l-e th y l a c e ta te m ixtu re are ad d ed a n d th e so lu tio n is allow ed t o sta n d in a n ic e b a th for 0 .5 hour w ith co n tin u o u s m ech a n ica l stirring. I t is esse n tia l th a t th e p recip ita tio n b e carried o u t a s in d ica ted . I f periodic acid is a d d ed t o th e a lc o h o l-e th y l a c e ta te so lu tio n , th e p recip ita te w ill be g e la tin o u s an d d ifficu lt to filter, w h ereas if it is first form ed in aq u eou s so lu tio n it is c ry sta llin e. T h e so lu tio n is filtered through a G ooch cru cib le an d th e p r ecip ita te w a sh ed w ith an h yd rou s e th y l a c e ta te w h ich h a s b een co o led t o 0 ° . I t is dried in th e o v en for 10 m in u te s a t 105° C ., cooled , an d w eigh ed .
I f v o lu m e tric resu lts are d esired, th e cru cib le w ith t h e pre-
T a b l e II. D e t e r m i n a t i o n o f P o t a s s i u m a s P e r i o d a t e i n P r e s e n c e o f F r e e A c i d
W t. of. K W t. of E r r o r in K
a s N itr a te A cid A d d ed K IO« G r a v im e tr ic V o lu m e tric
G ram G ram M g . M g .
0 .0 5 2 4 0 . 5 m l. co n c d . I I N O j 0 .3 0 9 2 + 0 . 2 0 .0 0 .0 2 8 9 0 . 5 m l. co n c d . IIN O » 0 .1 6 9 5 - 0 . 1 + 0 .1 0 .0 6 0 8 5 d ro p s I IjPO«, 8 5 % 0 .3 5 7 5 0 . 0 - 0 . 2 0 .0 5 6 1 5 d ro p s lh P O i, 8 5 % 0 .3 3 0 2 0 . 0 - 0 . 1
0 .0 5 7 2 1 m l. co n c d . H jPO * 0 .3 3 7 7 + 0 . 2 0 . 0
0 .0 6 0 3 -1 m l. co n c d . H1P O 4 0 .3 5 7 0 + 0 .4 + 0 .1 0 .0 4 6 1 5 d ro p s co n c d . H jS O i 0 .2 8 0 6 + 0 . 5 0 . 0 0 .0 5 8 0 5 d ro p s co n c d . I IjSO« 0 .3 4 0 8 - 0 . 1 + 0 . 1
0 .0 4 5 1 2 00 m g . H1B O 1 0 .2 6 5 8 + 0 . 1 0 . 0
0 .0 4 4 4 2 00 m g . I IjB Oi 0 .2 6 3 0 + 0 . 3 + 0 .3
0 .0 1 4 7 5 d ro p s H C 1 0 4l 70% « 0 .2 6 2 3 - 0 . 1 - 0 . 4
0 .0 5 4 1 5 d ro p s HCIO*. 70%® 0 .3 1 7 9 - 0 . 1 - 0 . 5
« S tir r e d 45 m in u te s .
c ip ita te is p la ced in a 25 0 -m l. beak er, to w h ich are a d d ed 125 m l. o f a so lu tio n co n ta in in g 5 gram s o f boric a c id an d 5 gram s of so d iu m tetr a b o r a te. T h e p o ta ssiu m p eriod ate d isso lv e s read ily in th is so lu tio n , w h ich h a s a p H o f a b o u t 7.5 . I t is u n n ecessa ry to ta k e th e crucible o u t o f th e so lu tio n .
W h en th e p o ta ssiu m p eriod ate h a s d isso lv ed , 3 gram s o f p o ta ssiu m io d id e are a d d ed an d th e iod in e is titr a te d w ith 0.1 ¿V arsen ite so lu tio n , prepared b y d isso lv in g 4 .9 4 5 g ra m s o f arsen ious oxid e in a so lu tio n o f 10 gram s o f so d iu m b icarb on ate, warm ed to a b o u t S 0° C . T h e so lu tio n is th e n sa tu ra ted w ith carbon d io x id e a n d d ilu ted to 1 lite r. A lth o u g h th e so lu tio n w as m ad e u p from arsen iou s o x id e o f k n o w n p u rity , it w a s sta n d a rd ized b y titr a tio n a g a in st pure p o ta ssiu m an d so d iu m p erio d a tes and th e v a lu e s ob ta in ed in t h is w a y w ere ta k e n a s correct. I n som e cases th e n o rm a lity foun d in th is w a y d e v ia te d from t h e th e o r e ti
cal v a lu e b y a s m uch a s 0 .0012.
P erio d ic acid w a s a lw a y s w eig h ed o u t in th e so lid form and d isso lv ed ju s t before u se t o a v o id a n y d an ger o f d eco m p o sitio n o n sta n d in g . G ravim etric resu lts w ere sa tisfa c to r y o n ly w h en a n itr a te w a s u sed , b u t w ere h igh w ith su lfa te s, th o u g h v o lu - m e tr ic a lly t h e su lfa te s d id n o t in terfere. T h e la tte r procedure is u su a lly p referable b eca u se i t is n o t affected b y th e p resen ce o f io d a te or o f in ert m aterials w h ich m a y b e in so lu b le in th e organ ic s o lv e n t.
W h en th e a m o u n t o f p o ta ssiu m p resen t is v e r y sm all, it is d e
sirab le t o in crease th e a m o u n t o f p eriod ic acid t o 1.5 or 2 gram s.
I f n o t m u c h so d iu m or oth e r m e ta l is p resen t, th e in itia l v o lu m e o f w ater sh ou ld b e d ecreased to 5 m l., a lth o u g h th is is n o t a b so lu te ly n ecessa ry . T h e tim e for p recip ita tio n sh o u ld b e in creased to 1 or 1.5 hours. I f less th a n 0 .4 m g . o f p o ta ssiu m is p resen t th e re
s u lts are un reliab le, e v e n th ou gh th e v o lu m e o f w a te r is reduced and th e a m o u n t o f periodic acid in creased .
R e s u lt s o f A n a ly s e s
In all the analyses described below, unless otherwise stated, the same conditions were used—namely, 90 ml. of solvent, 1 gram of periodic acid, 7 to 8 ml. of water, and 30 minutes stirring a t 0° C. The precipitate obtained was, in all cases, crystalline, and showed no tendency to adhere to the beaker. The results of a series of determ inations are shown in Table I.
I t is obvious th a t potassium can be completely separated from 70 mg. of sodium, b u t th a t there is a slight error when 140 mg. are present. I t was subsequently found th a t the lim it could be raised to 100 mg. By doubling the volume of alcohol-acetate mixture potassium was readily separated from 190 mg. of sodium.
E ffe c t o f T e m p e r a t u r e , S u lf a t e , a n d F r e e A c id In previous experiments the tem perature was 0° C. A series of experiments was run in which th e solutions were m aintained a t room tem perature for 15 and 60 minutes, respectively. In both cases the results were 0.2 to 0.6 mg.
too low.
Weights of potassium nitrate varying from 0.05 to 0.15 gram were taken and 40 mg. of sodium added as sulfate. In a series of 12 volumetric determ inations the error varied from
M arch 15, 1941 A N A L Y T I C A L E D I T I O N 139
—0.2 to + 0 .2 mg., w ith an average of practically zero. In this case th e gravim etric results were always too high be
cause of contam ination w ith sodium sulfate.
In Table I I are shown the results obtained when free nitric, phosphoric, sulfuric, perchloric, and boric acids are added.
In th e case of perchloric acid, some of the potassium is pre
cipitated as perchlorate and apparently is n ot quite converted into periodate within 45 minutes. The other acids do not interfere.
Ta b l e I I I . Se p a r a t i o n o f Po t a s s i u m f r o m Me t a l s a s Pe r i o d a t e
W t. of K W t. of E r r o r in K
aa N itr a te M e ta l A d d ed K IO« G r a v im e tr ic V o lu m e tric
G ram M g . G ram M g. M g .
0 .0 4 0 3 16 C a (aa n itr a te ) 0 .2 7 3 1 0 . 0 - 0 . 1
0 .0 5 3 0 32 C a (as n itr a te ) 0 ,3 1 1 9 0 . 0 - 0 . 1
0 .0 4 8 0 2 0 M g (a s su lfa te ) 21 M g (as n itr a te )
0 . 0
0 .0 4 6 4 0 Í2 7 3 2 + 0 . 1 0 . 0
0 .0 6 0 8 50 A1 (a s n itr a te ) 0 .3 5 7 9 0 .0 - 0 . 1
0 .0 6 1 5 100 A1 (a s n itr a te ) 0 .3 6 5 4 + 1.1 - 0 . 1
0 .0 4 5 2 102 A1 (a s n itr a te ) 0 .2 7 1 8 + 1 .0 0 . 0
0 .0 4 0 5 « 98 A1 (a s n itr a te ) 0 .2 4 6 8 + 0 . 5 + 0 . 1
0 .0 4 2 4 100 A1 (a s su lfa te ) 0 .2 5 3 0 + 0 .6 0 . 0
0 .0 4 0 0 100 A1 (as su lfa te ) 0 .2 3 8 3 + 0 . 3 + 0 .2
0 .0 4 8 4 62 Z n fas n itr a te ) 62 Z n (as n itr a te )
0 .2 8 7 6 + 0 . 5 - 0 . 1
0 .0 4 0 6 - 0 . 1
0 .0 4 9 8 92 C o (as n itr a te ) 8 8 C o (a s n itr a te )
0 Í2 9 5 9 + 6 !o - 0 . 2
0 .0 4 0 6 0 .2 4 0 0 + 0 . 2 + 0 .2
0 .0 4 2 3 77 N i (as n itr a te ) 0 .2 5 1 3 + 0 . 4 + 0 .2
0 .0 3 9 5 “ 79 N i (as n itr a te ) 0 .2 3 3 6 + 0 .2 + 0 . 2 0 .0 4 1 3 5 F e + + + (a s n itr a te ) 0 .2 7 7 3 + 5 .8 - 0 . 9 0 .0 3 5 8 5 F c + + + + 5 d ro p s
HaPO< 0 .2 3 5 5 + 4 .2 - 1 . 3
0 .0 5 7 9 50 M n (as su lfa te ) 0 .3 7 5 7 + 6 .0
0 .0 3 4 1 3 NH< (as n itr a te ) 0 .2 2 4 3 + 4 . 0 + 4 Í6
0 .0 5 1 6 60 L i (a s c a rb o n a te ) 0 .3 0 3 7 0 . 0
0 .0 4 0 1 69 L i (as c a rb o n a te ) 0 .2 3 7 1 + 0 . 2 - ó ! i
<* 180 m l. a lc o h o l-a c e ta to m ix tu r e u sed .
S e p a r a t io n f r o m O t h e r M e t a ls
The results in Table III show th a t volumetric determ ination of potassium is satisfactory in th e presence of moderate am ounts of magnesium, calcium, lithium, aluminum, zinc, nickel, and cobalt, b u t n o t ammonium, iron, manganese, and chromium. In the la tte r cases oxidation to perm anganate and chromate occurs and the titra tio n is not possible. The separations are b etter when 180 ml. of alcohol-acetate mix
ture are used. T he results are somewhat b etter when 8 ml.
of w ater rath er than 7 ml. are present.
T he gravim etric results are satisfactory w ith calcium (in the absence of sulfate), magnesium, and lithium.
Although calcium does n o t interfere when present as ni
trate, there is serious interference when it is present as sul
fate. N o t only was the reaction a t the end point slow, indi
cating th a t something was dissolving during the process, but the results were always too low. A pparently this is due to the form ation of th e insoluble double salt, CaSO^K^SO,!, so th a t it was impossible to convert all th e potassium to perio
date. This should be kept in mind if silicates have been de
composed by evaporation w ith hydrofluoric and sulfuric acids. A ttem pts to decompose feldspar by evaporation with hydrofluoric and phosphoric acids were unsuccessful.
The cobalt solution became green upon the addition of periodic acid. Ferric iron is readily precipitated as periodate and therefore interferes even when present in small am ounts.
I t was thought th a t the addition of phosphoric acid, forming a complex with the iron, would prevent its precipitation.
Although some effect was noticeable in the gravim etric re
sult, there was no improvement in the volumetric. In the absence of phosphoric acid the precipitate was brick-red, whereas in its presence it was white.
Rubidium and cesium behave like potassium, although no quantitative experiments were made.
In the presence of chromium and manganese, which are oxidized by periodic acid, th e color was so intense th a t no
titration was possible, although if not over 1 mg. of m anga
nese is present the end point can be seen.
The periodate m ethod is applicable to the determ ination of potassium in the mixed chlorides obtained by th e J. Law
rence Smith method, providing they are converted into ni
trates b y evaporation w ith nitric acid.
S u m m a r y
Potassium can be quantitatively precipitated as periodate by adding periodic acid to a solution only a few milliliters in volume and subsequently completing the precipitation by the addition of a much larger volume of a m ixture of equal p arts of aldehyde-free ethyl alcohol and anhydrous ethyl acetate.
The solution m ust be maintained a t 0° C. and stirred for 30 minutes.
T he precipitate of potassium periodate m ay be weighed or it m ay be dissolved in a boric acid-borax buffer, potassium iodide added, and th e free iodine titrated with arsenite. In this reaction the periodate is reduced to iodate.
Potassium m ay be separated from calcium, magnesium, zinc, aluminum, sodium, lithium, nickel, and cobalt, b u t not from manganese, iron, chromium, rubidium, cesium, and ammonium. I t is possible to separate as little as 0.4 mg. of potassium from seventy times as much sodium. If both calcium and sulfate are present the results are too low, prob
ably because of the formation of a double potassium calcium sulfate.
Small am ounts of sulfuric, phosphoric, nitric, and boric acids m ay be present, b u t w ith large am ounts th e precipitate becomes gelatinous and difficult to filter. In the presence of sulfate the gravim etric determ ination is impossible, b u t the volumetric method gives satisfactory results. Chloride m ust be absent.
The method is rapid and accurate.
A c k n o w le d g m e n t
The authors wish to express their thanks to R obert Mc
Nulty, who performed some of the analyses in Table I I I . L it e r a t u r e C ite d
(1) Greathouse, L. H ., dissertation, U n iversity of M ichigan, 1917.
(2) H ill, A . E ., J . A m . Chem. Soc., 50, 2678 (1928).
(3) M uller, E ., and Friedberger, O., B er., 35, 2652 (1902).
(4) Willard, H . H .. “Inorganic Syn th eses” , V ol. I , p. 172, N ew York, M cGraw-Hill Book Co., 1939.
(5) Willard, H . H ., and R alston, R . R „ T ra m . Electrochem. Soc., 62, 239 (1932).
(6) Willard, H . H ., and Thom pson, J. J., J . A m . Chem. Soc., 56, 1827 (1934).
Fr o m a th e sis p r e s e n te d b y A lb e r t J . B o y le to t h e G r a d u a te S ch o o l o f th e U n iv e rs ity of M ic h ig a n in p a r t ia l f u lfillm e n t of th e r e q u ir e m e n ts fo r th e d e g re e of d o c to r of p h ilo so p h y .
C o r r e c t i o n . T h e fo llo w in g correction s sh o u ld b e m a d e to F igure 1 of our a rticle, “ A n E lec tro n ic R e la y ” [ I n d . En g. C h e m . , A nal. E d ., 1 2 ,7 5 7 (1 9 4 0 )]:
1. In th e relay circu it o f F igu re 1, in te rch a n g e R i an d R ,".
2. In th e diagram o f th e tu b e so c k e t for th e O A 4G tu b e , m o v e th e ca th o d e (sm all circle) co n n e c tio n on e pin tow ard s th e right.
W e w ish to th a n k P rofessors W ad d le an d Serfas3 and D r . S h o m a te for calling our a tte n tio n to th e se errors.
Pa u l Fu g a s s i
C . E . R r o r , Jr.
