Industrial and Engineering Chemistry : analytical edition, Vol. 11, No. 6

IN D U S T R IA L

» i j p i u r . i i v r p n i i i r i :

alLU J U 1 1 J L 1 1 J i J O U 21,000 Copies of This Issue Printed

C H E M I S T R Y

I s s u e d J u n e 15, 1939

V o l. 31, C o n s e c u tiv e N o . 23

H a r r iso n E. H o w e , E d ito r V o l . 1 1 , N o . 6

De t e r m i n a t i o n o p Ni t r o g e n i n St a i n l e s s St e e l s . .

. . . . Thos. R. Cunningham and Harry L. Hamner 303

Te t r a p h e n y l a r s o n i u m Ch l o r i d e a s An a l y t i c a l Re­

a g e n t . . Hobart H. Willard and George M. Smith 305

De t e r m i n a t i o n o f Ri b o f l a v i n i n Mi l k b y Ph o t o­ e l e c t r i c Fl u o r e s c e n c e Me a s u r e m e n t s...

... David B. Hand 306

De t e r m i n a t i o n o p Ni c k e l a n d Co b a l t i n Si l i c a t e Ro c k s...E. B. Sandell and R . W. Perlich 309

Co n t r o lo p pH i n Pe r o x i d e So l u t i o n s...

...J. S. Reichert and H. G. Hull 311

Es t i m a t i o n o f Ni t r o g e n b y Kj e l d a h l Me t h o d . . .

... A. Sreenivasan and V. Sadasivan 314

An t i m o n y El e c t r o d e f o r In d u s t r i a l Hy d r o g e n- Io n Me a s u r e m e n t s...G. A. Perley 316

Ch a r a c t e r i s t i c s o f An t i m o n y El e c t r o d e...

G. A. Perley 319

De t e r m i n a t i o n o p As c o r b i c Ac i d ...

... Mary Mann Kirk and Donald K. Tressler 322

De t e r m i n a t i o n o f Te t r a e t h y l l e a d i n Ga s o l i n e . .

... George Calingaert and C. M. Gambrill 324

Se p a r a t i o n o f Co b a l tf r o m Ma n g a n e s e...

Wa r d e r’s Me t h o d f o r Ti t r a t i o n o f Ca r b o n a t e s . .

...A. A. Benedetti-Pichler, Michael Cefola, and Bernard Waldman 327

Du m a s Me t h o df o r Or g a n i c Ni t r o g e n...

... Fred Shea and C . E . Watts 3 3 3

Me t h o d s o f Re p r e s e n t i n g Di s t r i b u t i o n o f Pa r t i c l e • Si z e ... J . B . Austin 3 3 4

Im p r o v e d Fo r m o f Jo n e s Re d u c t o r...

... P. Nilakantan and N. Jayaraman 339

La r g e- Si z e Ex t r a c t o r f o r Li q u i d s...

...Frederick W. Schreiber 340

Mi c r o c h e m i s t r y :

Se r v i c e s o f Em i l e M . Ch a m o tt o Ch e m i c a l Mi c r o s­ c o p y ... 3 4 1

De t e r m i n a t i o n o f Bi s m u t hi n Bi o l o g i c a l Ma t e r i a l

...Donald M . Hubbard 3 4 3

Mi c r o i d e n t i f i c a t i o n o p Me t r a z o l e i n Mi x e d Aq u e o u s So l u t i o n s...Vincent E . Stewart 3 4 5

Mi c r o b i o l o g i c a l As s a y f o r Ri b o f l a v i n ...

...E. E. Snell and F. M. Strong 346

Mo d i f i e d Bu r e t f o r Mi c r o a n a l y s i s o f Ga s e s . . .

... David C . Grahame 351

Mo d e r n La b o r a t o r i e s:

Ba g l e y Ha l l, Un i v e r s i t y o f Wa s h i n g t o n...

... .W. L. Beusehlein 352 ... J. G. Fairchild 326

T h e A m erica n C h em ica l S o c ie ty a ssu m es n o r e sp o n sib ility for th e sta te m e n ts an d o p in io n s a d v a n c e d b y co n trib u to rs to it s p u b lica tio n s.

P u b l i c a t i o n O ffice* E a s t o n , P e n n a .

E d i t o r i a l O f f ic e : R o o m 7 0 6 , M ill s B u i l d i n g , W a s h i n g t o n , D . C . A d v e r t i 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 l e p h o n e : N a t i o n a l 0 8 4 8 . C a b l e : J i e c h e m ( W a s h i n g t o n ) T e l e p h o n e : B r y a n t 9 -4 4 3 0

P u b lish ed b y th e A m erica n C h e m ica l S o c ie ty , P u b lic a tio n Office, 2 0 th &

N o rth a m p to n S ts., E a s to n , P e n n a . E n tere d as seco n d -cla ss m a tte r a t th e P o st Office a t E a s t o n , P e n n a ., u n d er th e A c t of M arch 3, 1879, as 4 8 tim e s a year.

In d u stria l E d it io n m o n th ly on th e 1 st; A n a ly tica l E d itio n m o n th ly on th e 15th ; N e w s E d it io n on th e 1 0 th an d 2 0 th . A cc ep ta n ce for m a ilin g at sp e cia l r a te of p o sta g e p ro v id ed for in S ec tio n 1103, A c t of O ctober 3 , 1917, a u th o rize d J u ly 13, 1918.

Ra t e sf o e Cu r r e n t Nu m b e r s: A n n u a l su b scrip tio n rates: In d u s t r i a l a n d En g i n e e r i n g Ch e m i s t r yc o m p le te S6.00; (a) In d u stria l E d itio n S3.00;

(b) A n a ly tic a l E d itio n $ 2 .5 0 ; (c) N e w s E d itio n $ 1 .5 0 ; (a) an d (6) to g e th e r ,

$5 .0 0 . F o r eig n p o sta g e to c o u n tries n o t in t h e P a n A m erica n U n io n , $ 2 .4 0 ; (a) $ 1 .2 0 ; (b) $ 0 .6 0 ; (c) $ 0 .6 0 . C a n a d ia n p o sta g e o n e th ird th e s e ra te s.

S in g le cop ies: (a) $ 0 .7 5 ; (6) $0.50;^ (c) $ 0 .1 0 . S p ecia l ra tes t o m em b ers.

N o c la im s ca n b e a llo w ed for co p ie s o f jo u rn a ls lo s t in th e m ails u n less su c h claim s are re ceiv ed -within s ix t y d a y s o f th e d a te of issu e , an d n o c la im s w ill b e a llo w e d for issu e s lo s t as a r e su lt o f in su fficien t n o tic e of c h a n g e of ad dress. (T e n d a y s ’ a d v a n c e n o tic e requ ired .) " M issin g from files"

c a n n o t b e a cc ep te d as th e re a so n for h o n o rin g a cla im . C h a r les L . P a r so n s, B u sin ess M an ager, M ills B u ild in g , W a sh in g to n , D . C ., TJ. S . A .

4 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 11, NO. 6

Write fo r Catalog E-96(l)

L E E D S &. N O R T H R U P C O M P A N Y , 4920 S T E N T O N AVE., PH I LA., PA.

LEEDS & NORTHRUP

M EA SU R IN G IN STRU M EN TS

Jrl-A d E -9G (13)

T E L E M E T E R S • A U T O M A T IC CO N TRO LS • H E A T -T R E A T IN G FURN ACES

S a m p l e c u p is q u i c k l y f ille d . O n ly a 5 m l s a m p l e o f s o l u t i o n is n e c e s s a r y fo r

a c c u r a t e d e t e r m i n a t i o n s .

UNIVERSAL PH INDICATOR

FAST — SIMPL — EASY TO MANIPULATE

S tan d ard izatio n s an d com pensations are m ade individually . . . to a high degree o f accuracy. T h e y are quickly checked w henever desired.

S a m p l e h o ld e r s w i n g s i n t o p o s i t i o n a n d i s r a is e d t o i m m e r s e e l e c t r o d e t i p s . F i l l ­ i n g t h e c u p , i n s e r t i n g i t a n d i m m e r s i n g t h e e l e c t r o d e s t a k e s b u t a f e w s e c o n d s .

N o t only is th e o p e ra to r’s tim e saved by speedy operation, b u t w astes arising from incorrect p H values are m inim ized.

C u p is e a s il y p la c e d i n h o ld e r . E n t ir e c o r n e r o f t h e c a s e s w i n g s o u t l e a v in g h o ld e r a n d e l e c t r o d e s f r e e ly a c c e s s i b l e .

A n assurance of accuracy which accom panies sim ple, s tra ig h t­

forw ard operation comes to users o f th e U niversal p H In d icato r.

T h e logical, w ell-m arked sequence o f m an ip u latio n is quickly learned. K nobs and switches are easily accessible. M easu re­

m ents are m ade a t m axim um speed. B ecause o p eration is so easily u n d erstan d ab le, th e p ro b ab ility o f errors arising from faulty m an ip u latio n is p ractically non-existent.

P a rtic u la rly convenient is th e electrode c o m p artm e n t shown

a t the left. Sam ple cup and electrodes are freely accessible for

cleaning and filling. Solution is easily a g ita te d and equilibrium

is quickly reached. C up is positively positioned an d can n o t

touch electrodes when th ey are properly installed.

JUNE 15, 1939 ANALYTICAL EDITION 5

“ S u p e r - P u r i t y ’ ’

Achieved by Mallinckrodt Research

. . . ALUMINUM CHLORIDE ANHYDROUS A. R.

Pure W hite Cleanly Soluble

N o longer need you w ork w ith an A lum inum C hloride A nhydrous w hich is off-color an d jg iv es tu rb id solutions. M allin ck ro dt R esearch has produced th is A n aly tical R eag en t as a p u re w h ite pow der w hich is o u tsta n d in g for its

“ s u p e r-p u rity ” as evidenced by th e clarity of its solutions. Iro n has been lowered to th e m ax im u m lim it of 0.002% , H eav y M etals (as P b ) 0.001% , a n d Sulfate 0.002% .

U se th is im proved reag en t in yo u r lab o rato ry an d n o te its definite superiority. Send for th e M allinckrodt C atalog of A nalytical R eagents w here th e M axim um L im its of Im p u rities for n early 500 o th e r chem icals are published.

ST. LOUIS C H IC A G O

C H E M I C A L W O R K S

NEW Y O R K P H IL A D E L P H IA

INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 11, NO. 6

F or p y r o m e te r a c c u r a c y , h i t t h e n a il o n t h e h e a d —g o a ll t h e w a y . W ith yo u r C h r o m e l-A lu m e l c o u p le s , b e su r e to u se C h r o m e l-A lu m e l le a d s . . . . I f y o u u s e s o - c a lle d “ c o m p e n s a t in g ” le a d s , in s t e a d , y o u ’re a p t t o g e t a n error m o r e se r io u s t h a n y o u w a n t t o to le r a t e . T h e j u n c t io n w h e r e t h e le a d s a n d c o u p le s j o in o f t e n

g e t s very h o t , a n d t h a t ’s w h a t m a k e s t h e error. B u t w h e n t h e le a d s a n d c o u p le s are o f t h e s a m e m a t e r ia l, t h e te m p e r a tu r e o f th e ir j u n c t io n is o f n o s ig n ific a n c e . T h e n , th e r e is n o t h in g for w h ic h to c o m p e n s a t e . S o , fo r p y r o m e te r a c c u r a c y , s e n d fo r F o ld e r C -A . . . . H o s k in s M a n u ­ f a c t u r in g C o m p a n y , D e tr o it, M ic h ig a n .

C H R O M E L - A L U M E L

"Hit the Nail on the H ead"

JUNE 15, 1939 ANALYTICAL EDITION 7

T W O N e w A C E D E V E L O P M E N T S

F I B E R G L A S S F I L T E R S

M a d e E x c lu siv e ly U n d e r O u r U .S . P a t e n t N o . 2136170

A fter th ree years of research Ace offers over 100 filter disc item s previously o b tain ab le only from abroad.

Ace fiber glass filter discs are m ore rugged th a n sim ilar discs m ade of granules.

Ace fiber glass filter discs, P y rex b ra n d glass th ru o u t, are unaffected by corrosive solutions except hydrofluoric acid.

Ace filter crucibles, funnels, an d o th e r w are all featu re h eav y beaded constru ctio n increasing stren g th an d th u s reducing breakage.

Ind iv id ually tested for pore size.

A vailable in porosities 0. 1, 2, 3.

A C E S P H E R I C A L J O I N T S

P a t e n t A p p l ie d F or

F L E X I B L E — N O N F R E E Z I N G — IN T E R C H A N G E A B L E

These joints provide a positive seal superior to p resen t ta p ered jo in ts; elim inating th e need for lubricants, m etals a n d o th e r coverings.

T ap ered joints require an absolutely tru e align­

m en t while spherical jo in ts p e rm it a dev iatio n of 20°. T his facilitates all la b o ra to ry set-ups.

C hem ists well know of th e breakage a n d tim e lost in assem bling an d dism anteling a p p aratu s.

Spherical jo in ts are easily assem bled a n d come a p a rt im m ediately. T h is elim inates m ost breakage.

Sizes, inside diam eter of tube, 1, 1)4, 2, 3, 5, 7, 9, 11, 12, 15, 20, 25 m m .

A dapters can be supplied p e rm ittin g use of spherical joints w ith p resen t “ S ta n d a rd T a p e r”

joints.

S p e c ia lly d e s ig n e d c la m p s a r e a v a ila b le f o r th e s e j o i n t s .

ACE GLASS INC.

VINELAND, N. J.

M A N U F A C T U R E R S O F L A B O R A T O R Y G L A S S W A R E

O b ta in a b le fr o m le a d in g L a b o r a to r y S u p p ly D e a le r s

8 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 11, NO. 6

A A New High-Precision Unit

A N N O U N C I N G for X-Ray Diffraction

G ENERAL ELECTRIC X -R A Y C O R PO R A T IO N

W

tria l science fo r a co m pact, v e rsa tile , safe a p p a ra tu s fo r a p p lic a tio n o f x-ray d iffractio n m e th o d s to a m u ltitu d e o f in d u s tria l a n d re se a rc h p ro b lem s.

T h e X R D em b o d ies fe a tu re s w h ic h satisfy th e m ost rig o ro u s specifications fo r p re c isio n re se a rc h a n d con­

tr o l w ith o u t sacrificing th e re q u ire m e n ts fo r safety, co n v en ien ce, sim p licity , com p actn ess, flex ib ility , ease o f o p e ra tio n , a n d a d a p ta b ility th a t m a k e f o r econom ­ ical a p p lic a tio n o f a m e th o d o ffering g re a t advantages to th e c h e m ist a n d m e ta llu rg ist. T e d io u s la b o r in v o lv ed in m o u n tin g sp ecim en s, re g iste rin g d iffractio n p a tte rn s, a n d o p e ra tin g th e a p p a ra tu s h a s b e e n la rg e ly e lim in a ­ te d in th e desig n o f th is n ew G -E X -R ay u n it, th u s a l­

lo w in g th e o p e ra to r to sp e n d h is tim e p la n n in g re se a rc h ro u tin e , p re p a rin g specim en s, a n d in te rp re tin g resu lts.

A ll e le c tric a l p a rts a re c o m p le te ly en clo sed , to p ro v id e th e u ltim a te in e le c tric a l safety. A n d y e t th e en erg izin g e q u ip m e n t is c a p ab le o f o p e ra tin g th e m o st p o w e rfu l x-ray d iffractio n tu b e s c o m m ercially a v a ila b le to d ay . B u ilt p rim a rily to p ro v id e lo n g , re lia b le , eco n o m ical service, th e little d e ta ils w h ic h m a k e fo r c o n v e n ie n c e - su ch as th e e le c tric c lo c k w ire d in to th e c irc u it fo r tim in g ex p o su res, a n d th e ru b b e r-tire d casters w h ic h m ak e i t easy to m o v e a b o u t—h av e n o t b e e n fo rg o tten . In fa c t th e r e a re d o zen s o f th e m w h ic h th e in d u s tria l sc ie n tist w ill reco g n ize in s ta n tly , a n d a p p re c ia te even m o re as h e u ses th e u n it.

A new catalo g d e sc rib in g th e G-E M o d el X R D a n d accessory item s, a n d in c lu d in g m u c h v a lu a b le in fo r­

m a tio n co n c e rn in g th e p o ssib le a p p lic a tio n s o f x-ray diffractio n , is ju s t off th e p ress. W rite f o r y o u r copy to d ay . J u s t a s k fo r P u b lic a tio n N o. I 96.

More Compact , More Versatile , Completely Safe

JUIVE 15, 1939 ANALYTICAL EDITION 9

MERCK REAGENTS USED IN THE CHEMISTRY OF IRON

M n — S o d iu m B is m u t h a te — a ssa y

85%

<^.0005%

A m m o n iu m P e r s u lf a t e — M n <^.001%

P — A c id M o ly b d ic — a ssa y 8 5 % — fr e e fr o m C o p p e r M a g n e s iu m C h lo r id e — < ^ .0005% P

A m m o n iu m C h lo r id e —< ^ .0002% P

S i— A c id P e r c h lo r ic 6 0 & 7 2 % — n o t m o r e th a n 0 0 0 % S1O2 S — C a d m iu m C h lo r id e — < ^ .0015% S

B a r iu m C h lo r id e — c le a r ly s o lu b le

M e r c k R e a g e n t M in e r a l A c id s a n d A m m o n ia W a te r are m a r ­ k e te d in " p o u r - c le a n ” b o ttle s w ith n e w ly d e v e lo p e d , n o n ­ le a k in g a n d e a s ily r e m o v a b le p la s tic s c r e w c a p s.

M E R C K & C O . Inc. ^ /e n ititô R A H W A Y , N . JL

N ew Y o rk ■ P h ila d e lp h ia • St. Louis • In C an ad a: M erck & C o. L td., M o n tre a l a n d T o r o n to From iron ore to pig and cast irons,

the chemist and the metallurgist are dom inant factors in the control o f the process and finished products.

A strong, cough, even-grained metal, yet soft enough to drill and cut, are quality factors dependent upon the constituent impurities in the ore, or their elimination through the chemistry of the blast furnace process. W hether the iron be foun­

dry pig, cast iron pipe, cast iron locomotive cylinders, chilled cast iron wheels, malleable castings, gray iron castings—Merck Analytical Re­

a g e n ts g u id e th e all im p o r ta n t C-Mn-P-Si-S balance.

10 INDUSTRIAL AND ENGINEERING CHEMISTRY YOL. 11, NO. 6

A. H. T . CO. S P E C IF IC A T IO N

E L E C T R IC S T IR R IN G APPARATUS

D IR EC TLY CONNECTED TO A VARIABLE SPEED, UNIVERSAL MOTOR

ELECTRIC ST IR R IN G A PPA R A TU S, Variable Sp eed , A .H .T . Co. Specification. C o n sistin g of Vioo h .p . u n i­

v e rsa l m o to r w ith sp eed c o n tro l rh e o s ta t, a d ju s ta b le chuck, M o n el m e ta l s tirrin g ro d , a n d hollow s u p p o rtin g a rm , 8 inches lo n g X '/V in c h o u tsid e d ia m e te r, fo r fa ste n in g th e c o m p le te u n it to a s u p p o rt s ta n d in a n y d e sire d p o sitio n o r angle b y m ean s of th e u su al clam p h o ld er.

W ith r h e o s ta t enclosed in v e n tila te d m e ta l cage 2 -l/ 4 inches h ig h , m o u n te d on to p of th e m o to r, a n d co n tro l k n o b p ro te c te d fro m excessive h e a t b y a co n cealed asb esto s disc. S tirrin g u n it is finished in b rig h t b lack A lum ilite.

T h e c h u ck ta k e s 3/ u o r V -rinch s tirrin g ro d s, of eith er m e ta l o r glass of th e v a rio u s ty p e s su ch as liste d u n d e r our N o. 9245, a n d p ro v id e s a p p ro x im a te ly I - V2 inches of b e a r­

ing su rface so t h a t e x tra lo n g s tirre rs c a n b e u sed w ith m in im u m v ib ra tio n a t th e pro p eller. A Vg-inch hole in th e s ta tio n a ry p o rtio n of th e ch uck, fo r in se rtio n of a lev er, m ak es i t possible to release th e s tirre r a fte r long a n d co n ­ tin u o u s use.

F o u r lite r q u a n titie s of 10% A lu m in u m H y d ro x id e so lu tio n h a v e b een th o ro u g h ly m ix ed w ith th is s tirre r.

W ith lig h te r lo ad s, th e speed can be v a rie d fro m a few re v o lu tio n s to 4000 r.p .m .

9234-E. Stirring Apparatus, Electric, A.H.T. Co. Specification, as above described, with Monel metal stirring rod 9 inches long X

34

Code Word... Oikiv

10% discount in lots of 12.

9234-G. Stirring Assembly, complete as shown in above illustration, consisting of 9234-E Stirring Apparatus, mounted by means of Fisher Castaloy clamp holder on 9341-H Support with Coors porcelain horseshoe type base and rod of aluminum alloy, but without glass beaker. The Alumilite finished Stirring Unit with Monel metal stir­

ring rod, in combination with porcelain base support with Alumilite finished rod and Castaloy clamp holder, provides a rust-resisting assembly... 17.05 Code Word... Oikkr

9341-H. Support, only, with horseshoe type base of solid Coors porcelain on rubber feet, with rod of aluminum alloy with Alumilite finish. Base is inches long X 7}/g inches wide, with 4% inches clearance between feet. Rod is 24 inches long X H inch diameter. The porcelain base is glazed except on bottom surface, making it easy to keep clean and impervious to the reagents in common laboratory use...3.25 CodeW ord... Oloye 10% discount in lots of 10; 15% discount in lots of 50; 20% discount in lots of 100

ARTHUR H. TH O M AS COMPANY

R E T A IL — W H O LE SA LE— E X P O R T

LABORATORY APPARATUS AND REAGENTS

W EST W ASHIN GTO N SQUARE, P H ILA D E L P H IA , U .S .A . C able A ddress, " B a la n c e ,” P h ilad elp h ia

INDUSTRIAL ..a ENGINEERING CHEMISTRY

ANALYTICAL EDITION I la r r ls o n E. H o w e . E d ito r

Determination o f Nitrogen in Stainless Steels

T H O S . R . C U N N IN G H A M , E le c tr o M e t a llu r g ic a l C o m p a n y , A N D H A R R Y L . H A M N E R , U n io n C a r b id e a n d C a r b o n R e s e a r c h L a b o r a to r ie s , I n c ., N ia g a r a F a lls , N . Y .

T

curate method for determining this element. The Allen method (1) for combined nitrogen in plain carbon steels con­

sists in dissolving the sample of metal in the form of drillings or millings in hydrochloric acid (sp. gr. 1.11), making the solu­

tion alkaline with calcium oxide, distilling off the ammonia, and completing the determination with Nessler’s solution.

Among the authors who have employed modifications of Allen’s method are Tschischewski (-5), Weiss and Englehardt (6), Ruff and Eisner (4), Johnson (2), and Jordan and Swindell (3). Jordan and Swindell’s modification of Allen’s

The amounts of nitrogen th a t were found in the acid-insolu­

ble portions of several stainless steels are shown in Table I.

This table also shows th a t results for nitrogen by the authors’

modification of Jordan and Swindell’s method agree very well with the results obtained by the vacuum fusion method. The method to be described has been used by this and other laboratories since 1932.

M e th o d

Five grams of the sample are transferred to a large platinum dish (300-ml.) provided with a tight-fitting cover, and treated with 50 to 60 ml. of dilute hydrochloric acid (1 to 1, prepared

Ta b l e I. An a l y s i s o f Ti t a n i u m a n d Co l u m b i u m ( Pl u s Ta n t a l u m) St a i n l e s s St e e l s r o n Ni t r o g e n

--- N itr o g e n ---.

A cid A cid T o ta l — C o m p o sitio n o f S te e l---

T y p e o f S te el s o lu b le in so lu b le N Cr N i c C b T a T i M n Si

% % % % % % % % % % %

1 8 - 8 + C b 0 .0 3 1 0 .0 1 5 0 .0 4 6 1 7 .8 1 9 .1 8 0 .0 7 0 .7 5 0 .0 9 N o t

o v er 0 .0 1

0 .5 2 0 . 3 6

1 8 - 8 + C b 0 .1 5 0 .0 7 0 ,2 1

0 . 2 2 “ 1 8 .1 8 8 .8 0 0 .0 6 2 1 .1 0 0 .0 4

1 8 - 8 + T i 0 .0 0 6 0 .0 4 2 0 .0 4 8 1 8 .2 1 9 .1 7 0 .1 5 8 1 .5 6 0 .3 1 0 . 5 4

2 4 Cr + T i 0 .0 0 9 0 .3 0 0 0 .3 0 9

0 .3 0 9 « 2 3 .9 8 0 .1 0 4 •• ^{1 .3 6}

2 4 C r + T i 0 .0 1 1 0 .2 7 0

° R e s u lts o b ta in ed b y v a cu u m fu sio n .

0 .2 8 1 2 3 .6 7 1 .1 8 0 .0 9 4 1 .2 7

method, which consists in dissolving the sample in hydro­

chloric acid (sp. gr. 1.11), adding a strong solution of potas­

sium hydroxide, distilling the ammonia over into a measured excess of standard sulfuric acid, and titrating the excess acid with alkali, is applicable to most stainless steels, provided they do not contain any metals such as titanium, columbium, tantalum , tungsten, or vanadium, which form acid-insoluble nitrides. Tschischewski (5) stated th a t in a 0.35 per cent silicon and 0.84 per cent manganese steel he found a residue insoluble in hydrochloric acid th a t contained 0.000125 per cent of nitrogen. The authors have experienced no inter­

ference due to silicon, which undoubtedly is because of the use of hydrofluoric acid in the initial solution of the sample.

However, the nitrogen in a titanium -treated steel, provided sufficient titanium is added, will be found almost entirely in the hydrochloric acid-insoluble residue. If the steel is alloyed with columbium, tantalum , or vanadium, only part of the nitrogen will be in the insoluble residue. Since one or more of these elements are frequently present in stainless steels, it is never safe to omit testing any acid-insoluble residue for nitro­

gen.

by mixing ammonia-free water with hydrochloric acid, sp. gr.

1.19, from a fresh bottle that has just been opened), a little at a time, until the violent reaction ceases. Three milliliters of hy­

drofluoric acid (48 per cent, from a freshly opened bottle) are next added and the dish and its contents are heated on a hot- water bath until the solution of the alloy is practically complete.

Should the alloy dissolve completely in the hydrochloric acid, the addition of hydrofluoric acid may be omitted and the solution of the alloy may be effected in a 150-ml. covered beaker.

While the alloy is being dissolved, 100 ml. of sodium hydroxide (500 grams per liter), several small pieces of mossy zinc, about 400 ml. of water, and 20 grams of tartaric acid are transferred to a 500-ml. Kjeldahl flask connected to a spray trap and a block- tin condenser. The apparatus used is shown in Figure 1. Two hundred milliliters of the solution are distilled over and discarded, and the alkaline solution in the Kjeldahl flask is then allowed to cool.

The solution of the alloy is removed from the hot-water bath, allowed to cool, and added to the sodium hydroxide solution in the Kjeldahl flask. The tartaric acid previously added to the alkaline solution serves to hold most of the iron and chromium in solution and thus makes the distillation much easier. The dish is rinsed successively with four 50-ml. portions of ammonia-free water. The contents of the flask are then boiled until 200 ml. of the distillate have passed over. The distillate is collected in 25 ml.

or more of standard 0.02 N hydrochloric acid, depending upon 303

Fi g u r e 1. Di a g r a m o f Ap p a r a t u s

the nitrogen content of the alloy. The excess of acid is titrated with standard 0.02 Ar sodium hydroxide solution. Two drops of a 1 per cent aqueous solution of sodium alizarin sulfonate are used as an indicator. The end point is marked by the complete disappearance of the clear yellowish green color, or the first indication of a brown. Each milliliter of 0.02 N hydrochloric solution is equivalent to 0.00028 gram of nitrogen. A blank is run on all the reagents used and any nitrogen found is deducted.

For steels containing very low percentages of nitrogen, solutions weaker than 0.02 N are used.

Should the steel contain vanadium, titanium, columbium, tan­

talum, or any other metals known to form a nitride insoluble in hydrochloric acid the solution obtained as described in the first, paragraph should be filtered on a 9-cm. filter and the residue washed well with 1 per cent hydrochloric acid. The nitrogen in the filtrate is determined as described in paragraphs 2 and 3. The paper and insoluble residue are transferred to a 500-ml. Kjeldahl flask, 10 grams of potassium sulfate, 1 gram of copper sulfate, and 20 ml. of sulfuric acid (sp. gr. 1.84) are introduced, and the flask and its contents are heated just below the boiling point of the acid until all frothing ceases. x\t no time during the digestion should the part of the flask above the surface of the liquid be heated. The liquid is next heated to boiling and the boiling con­

tinued for from 15 to 30 minutes after the solution has become colorless. The solution is allowed to cool, 200 to 250 ml. of am­

monia-free water are added, the flask is connected to the con­

denser, 150 ml. of 10-per cent sodium hydroxide solution are added, and the nitrogen in this solution is determined as de­

scribed in paragraph 3. A blank is run on all the reagents used, including the filter paper, and any nitrogen so found is deducted.

Any nitrogen found after deducting the “blank” is added to that obtained by acid solution of the sample and distillation, to ob­

tain the total nitrogen.

Ammonia-free water is prepared by dissolving 200 grams of potassium hydroxide and 8 grams of potassium permanganate in 1100 ml. of distilled water and boiling the solution until the volume has been reduced to approximately 1000 ml. This solu­

tion is added to the water to be purified in the ratio of 1 to 10.

Distillation is then carried on until a test of 100 ml. of the distil­

late does not require more than 1 or 2 drops of 0.02 Ar hydro­

chloric acid solution. Two drops of a 1 per cent aqueous solution of sodium alizarin sulfonate are used as the indicator.

L ite r a tu r e C ited

(1) Allen, A. II., J . Iron Steel h ist. (London), 8, 1S1 (1S80).

(2) Johnson, C. M ., Iron Age, 134, (Ju ly 26, 1934).

(3) Jordan, L., and Swindell, F. E., N atl. B ur. S tandards, Sci. Paper 457 (Nov. S, 1922).

(4) Ruff, O., and E isner, F., Her., 41, 2252 (1908).

(5) Tschischewski, N., J . Iron Steel In st. (London), 92, P a r t II, 47-90 (1915).

(6) Weiss, L., and E nglehardt, T ., Z. anorg. Chem., 65, 3S-104 (1909).

Pr e s e n t e d b efo re th e D iv is io n of P h y s ic a l an d In o r g a n ic C h e m is tr y a t th e 9 7 th M e e tin g of th e A m eric a n C h e m ica l S o c ie ty , B a ltim o r e , M d .

C o r r e c tio n

In an article entitled, “A Modification of the Berl-Kullmann Melting Point Block” [ In d. En g. Ch e m., Anal. E d . , 9 , 3 4 0 ( 1 9 3 7 ) ] failure was inadvertently made to mention an article by Matthaus and Sauthoff [Chem. Fabrik, 8 , 9 2 ( 1 9 3 5 ) ] , who have designed a block in which reflections from the surface of the melting point tube are eliminated by illumination from above. Unfortunately, this article was not abstracted by the American or British abstracts, upon which dependence was placed in the literature search (an abstract was later found in Centralblatt) . The author wishes to acknowledge the priority of Matthaus and Sauthoff in regard to the feature of the block mentioned.

F . W . Be r g s t r o m St a n f o r d Un i v e r s i t y, Ca l i f.

A pril 2 4 , 1939

INDUSTRIAL AND ENGINEERING CHEMISTRY

Tetraphenylarsonium Chloride as an Analytical Reagent

D eterm ination o f R henium

H O B A R T H . W IL L A R D A N D G E O R G E M . S M I T H 1 U n iv e r s it y o f M ic h ig a n , A n n A rb o r , M ic h .

T

(C6H6)4As+ + R e04~ = (CeHsJjAsReOj

to form a white, crystalline precipitate which is insoluble in cold water. This permits the quantitative determination of perrhenate both potentiometrically, by the titration of the excess reagent with iodine (1), and gravimetrieally. The latter is usually more convenient and is the method described in this paper. The potentiometric titration is, however, equally satisfactory.

The determination is carried out by adding an excess of tetraphenylarsonium chloride to the perrhenate, keeping the volume as small as possible. The precipitate, which is allowed to stand several hours, preferably overnight, is filtered through a Gooch crucible, washed several times with ice water, dried, and weighed as (CoIIs^AsReOi. The pre­

cipitation is carried out in a hot solution, in the presence of a neutral salt, such as sodium chloride or sodium sulfate, to make the precipitate more granular and more easily trans­

ferred. The most satisfactory precipitation medium is 0.5 molar sodium chloride. Nitrates, except in very low con­

centration, should be avoided because of the limited solubility of tetraphenylarsonium nitrate.

Ta b l e I . Gr a v i m e t r i c De t e r m i n a t i o n o f Pe r r h e n a t e (V o lu m e , 25 t o 60 m l.; N a C l, 0 .5 m olar)

, ; P e rrh en a te--- .

P r e s e n t F o u n d E rror

M g. M g. M g .

0 .4 4 0 . 4 0 - 0 . 0 4

0 .8 9 0 .9 1 +0 . 0 2

1 .3 3 1 .2 6 - 0 . 0 7

1 .7 8 1 .8 2 + 0 . 0 4

2 . 2 2 2 . 2 1 -0 . 0 1

4 . 4 4 4 . 4 3 -0 . 0 1

1 3 .3 2 1 3 .3 3 +0 . 0 1

1 7 .7 6 1 7 .8 2 + 0 . 0 6

2 2 . 2 1 2 2 . 2 1 ±0 . 0 0

2 2 . 2 1 2 2 .1 7 - 0 . 0 4

4 4 .4 1 4 4 .3 9 -0 . 0 2

8 8 .8 2 8 9 .0 0 + 0 . 1 8

1 3 3 .2 4 1 3 3 .1 8 - 0 . 0 6

Determinations were attem pted in the presence of most of the common anions and cations. Anions, such as perman­

ganate, periodate, perchlorate, thiocyanate, iodide, bromide, and fluoride, which unite directly with the tetraphenyl­

arsonium ion to form insoluble compounds, should be absent.

Those cations the halide complexes of which form insoluble tetraphenylarsonium compounds in the presence of 0.5 molar chloride ions interfere except in very low concentra­

tion. High concentrations, approaching saturation, of any substance should be avoided to prevent the precipitation of excess reagent. In general, the presence of other substances in solution causes the formation of a precipitate which is more easily transferred.

P r o c e d u r e

In all determinations a standard solution, made by dissolving pure potassium perrhenate in water containing 8.8824 mg. of perrhenate ion per ml. was used. To a definite volume of the hot solution, containing sufficient sodium chloride to make the

‘P r e s e n t a d d ress, V a n d er b ilt U n iv e r s ity , N a sh v ille , T en n .

final solution about 0.5 molar, a measured excess of tetraphenyl­

arsonium chloride is added. The total volume should be 25 to 00 ml. The mixture is stirred and allowed to stand several hours, preferably overnight.

The precipitate is filtered through a Gooch crucible, washed several times with ice water, and dried at 110° C. It is weighed as tetraphenylarsonium perrhenate, ( C6H : ,) ,iA s R c O i. Multiply­

ing by the factor 0.3952 converts this weight to perrhenate, R e04~.

Ta b l e II. Ef f e c t o f Ac i d i t y a n d An i o n s o n Pe r r h e n a t e De t e r m i n a t i o n s

(R eO <", 2 2 .21 m g .; t o ta l v o lu m e , 25 to 3 0 m l.)

S u b sta n c e M olar P errh en a te

P r ese n t C o n c en tra tio n Error, M g .

HC1 0 . 5 + 0 . 0 4

HC1 4 . 8 + 0 . 0 8

H N O a 0 . 7 + 1 . 5 4

h2s o < 0 . 8 + 0 . 0 9

H2SOi 3 . 6 + 1 .3 0

H3P O4 0 . 8 + 0 . 0 7

H C2H i 02 6 . 9 + 0 . 1 9

C itr ic acid 0 . 2 0 .0 0

T a rta r ic acid 0 . 6 + 0 . 0 8

O xalic acid 0 . 3 +0 . 1 0

N a iS O i 0 . 5 - 0 . 0 1

NajW O« 0 . 1 + 0 . 0 4

N aiH P O * 0 . 1 -0 . 1 1

N H4OH 6 . 0 + 0 . 0 3

N a O H 0 . 5 - 0 . 2 6

In this way quantities of perrhenate varying from 0.40 to 133 mg, have been determined with satisfactory accuracy in the presence of various other ions. Typical data are shown in Table I. M any of these gravimetric results were dupli­

cated by the potentiometric titration of the excess of reagent with iodine.

Ta b l e I I I . Ef f e c t o f Ca t i o n s o n De t e r m i n a t i o n o f Pe r­ r h e n a t e ( In c l u d i n g Me t a v a n a d a t e, V 0 3~)

(V o lu m e, 2 5 to 3 5 ml. N a C l, a b o u t 0 .5 m olar)

Ion Q u a n tity P errh en a te

P r esen t of Ion P r e se n t F o u n d E rror

Mg . M g. M g. Mg.

A1 + + + 112 2 2 .2 1 2 2 .1 3 - 0 . 0 8

B a + + 56 5 4 4 .4 1 4 4 .3 4 - 0 . 0 7

C a + + 36 0 4 4 .4 1 4 4 .3 4 - 0 . 0 7

C d + + 440 2 2 .2 1 2 2 .1 7 - 0 . 0 4

C o + + 2 10 1 .3 3 1 .2 6 - 0 . 0 7

C r + + + 215 4 4 .4 1 4 4 .5 0 + 0 . 0 9

C u + + 25 5 4 4 .4 1 4 4 .3 4 - 0 . 0 7

F e + + 200 2 .2 2 2 .2 9 + 0 . 0 7

F e + + + 206 2 .2 2 2 .1 3 - 0 . 0 9

F e + + + 2 06 4 4 .4 1 4 4 .3 4 - 0 . 0 7

M g + + 100 2 2 .2 1 2 2 .2 1 0 .0 0

M n + + 2 75 2 2 .2 1 2 2 .2 1 0 .0 0

N i + + 2 5 0 2 2 .2 1 2 2 .1 3 - 0 . 0 8

Sb + + + 3 66 2 2 .2 1 2 2 .1 7 - 0 . 0 4

U 0 2 + + 635 2 2 .2 1 2 2 .3 0 + 0 . 0 9

v o ++ 20 0 4 4 .4 1 4 5 .0 1 + 0 . 6 0

V O + + 800 2 2 .2 1 2 3 .6 7 + 1 .4 6

v o ++ 1000 4 .4 4 6 .9 7 + 2 .5 3

V 0 3 - 35 4 4 .4 1 4 4 .5 7 + 0 . 1 6

V 0 3 - 6 50 2 2 .2 1 2 2 .3 1 + 0 . 1 0

V 03- ^{5 20 4 .4 4} 4 .5 5 + 0 . 1 1

Zn + + 2 60 2 2 .2 1 2 2 .1 7 - 0 . 0 4

Similar determinations were satisfactorily made under conditions of acidity varying from weakly alkaline to fairly strongly acidic. Sodium hydroxide has a solvent action on the precipitate, b u t a relatively high concentration of am­

monium hydroxide is not harmful. Nitric acid or nitrates, except in very low concentration, will cause coprecipitation of tetraphenylarsonium nitrate with the perrhenate. High results are obtained with high concentrations of hydrochloric

306 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 11, NO. 6 acid or other acids, probably because of the decreased solu­

bility of the reagent under such conditions. Bromide, iodide, and fluoride, in more than traces, should be absent. Tung- state does not interfere. Results are shown in Table II.

Ta b l e IV . Ef f e c t o f Ni t r a t e a n d Mo l y b d a t e o n Pe r r h e n a t e De t e r m i n a t i o n

(V o lu m e, 2 0 t o 35 m l.; N a C l, a b o u t 0 .5 m olar) C o n c e n ­ P e rrh en a te

S u b s ta n c e P r ese n t tr a tio n P r e se n t F o u n d E rror

M g. M g. Mg .

N H4NO* 0 . 5 M 4 4 .4 1 5 0 .9 8 + 6 . 5 7

N a N O s 0 . 3 M 2 2 .2 1 2 5 .7 7 + 3 . 5 6

N aN O a 0 .0 1 6 M 2 2 .2 1 2 2 .4 0 + 0 . 1 9

N aN O * 0 . 1 M 0 .8 9 0 .9 1 + 0 . 0 2

N a N O j 0 . 0 5 M 0 .4 4 0 .4 0 - 0 . 0 4

M g . M o O 2

M oO * 4- 4 m l. NH <O H 3 15 2 2 .2 1 2 2 .1 3 - 0 . 0 8

M oO * + 3 g . ta r ta ric acid 3 15 2 2 .2 1 2 2 .2 1 0 .0 0

M oO* + 4 m l. N H4OH 210 2 .2 2 ~2 . 25 + 0 . 0 3

M oO* 4* 4 m l. N H4O H 210 4 4 .4 1 4 4 .3 4 - 0 . 0 7

M oO * 4- 3 g . ta r ta ric acid 2 10 4 4 .4 1 4 4 .2 6 - 0 . 1 5

M oO * + 4 m l. N H4O H 100 0 .4 4 0 .4 0 - 0 . 0 4

M oO * 4* ^{4 m l.} NH4OH ^{100 2 22 2 .2 1 - 0 . 0 1}

M oO* + 2 m l. NH4OH ^{100 2 2 .2 1} 2 2 .2 9 + 0 . 0 8

M oO j + 2 m l. N H4O H 20 2 2 .2 1 2 2 .1 7 - 0 . 0 4

MoO* 100 2 2 .2 1 1 2 0 .2 6 + 9 8 . 0 5

I n te r fe r in g S u b s t a n c e s

The effect of the presence of various cations is shown in Table III. Only those ions interfere which form insoluble chlorides or whose complex halides form insoluble salts with tetraphenylarsonium ion. These include mercuric, stannic, bismuth, tellurium, lead, vanadyl, and silver. Cadmium and zinc do not interfere if the chloride-ion concentration is low. M etavanadate ion in fairly high concentration does not interfere. All these ions serve to make the precipitate more granular.

The presence of nitrate even in small quantities m ay cause serious interference if the quantity of perrhenate is fairly large. However, the interference is not so pronounced for very small amounts of perrhenate. I t is practically impossible to wash out all traces of tetraphenylarsonium nitrate from the heavier perrhenate precipitate. Typical data are shown in Table IV.

M olybdate ion forms a fairly insoluble precipitate with tetraphenylarsonium ion, but this precipitation is hindered or prevented altogether in the presence of ammonium hy­

droxide, tartrates, citrates, and their acids. Typical data are shown in Table IV.

S u m m a r y

From 0.40 to 133.0 mg. of perrhenate ion can be determined gravimetrically with tetraphenylarsonium ion, in moderate, excess, in volumes from 25 to 60 ml.

The presence of a small amount of sodium chloride, about 0.5 molar, or of other salts, and heating before precipitation are very effective in producing a crystalline precipitate which is easily transferred and washed.

Accurate determinations may be made in solutions varying from strongly ammoniacal to fairly strongly acidic.

Permanganate, perchlorate, periodate, iodide, bromide, fluoride, thiocyanate, mercury, tin, vanadyl, and bismuth ions interfere.

N itrate m ust be absent in all but very low concentrations.

Interference by molybdate m ay be avoided by the use of ammonium hydroxide or tartaric acid.

L it e r a tu r e C ite d

(1) W illard and Sm ith, In d. En g. Ch e m., A nal. E d ., 11, 186 (1930).

Determination o f Riboflavin in Milk

By P h otoelectric F lu orescen ce M easurem ents

D A V ID B . H A N D , C o r n e ll U n iv e r s it y , I t h a c a , N . Y .

R ib o fla v in in m ilk w a s d e t e r m in e d b y a d d in g 50 m l . o f a c e t o n e t o 25 m l . o f m ilk , f ilt e r in g , a n d c o m p a r in g t h e flu o r e s c e n c e o f t h e f ilt r a t e w i t h t h a t o f a c u b e o f u r a n iu m g la s s w h ic h h a d p r e ­ v io u s ly b e e n c a lib r a t e d a g a in s t s o l u t i o n s c o n t a i n ­ i n g k n o w n a m o u n t s o f r ib o fla v in . T h e c o m p a r is o n o f flu o r e s c e n c e w a s m a d e w i t h a p h o t o e le c t r ic c e l l a n d m ic r o a m m e t e r , u s in g s u it a b le g la s s filte r s .

R

zyme (15, 17), as a hydrogen acceptor (16), and as a photo­

sensitizer for the oxidation of vitamin C in milk by light (5, 6, IS). The riboflavin content of milk can be determined rapidly and accurately by using suitable light filters and standards and measuring w ith a photoelectric cell and micro­

ammeter the fluorescence produced in a filtered acetone ex­

tract of milk or whey.

Methods for the determination of riboflavin so far de­

scribed have involved visual estimation of color or fluorescence

intensity by comparison with standards, or photoelectric measurement of either light absorption or fluorescence in­

tensity. Charité and K haustov (1) compared riboflavin ex­

tracts with a standard solution of potassium chromate in a colorimeter. Kuhn, Wagner-.Jauregg, and K altschm itt (11) determined the chloroform-soluble, photochemical de­

composition product w ith a stage photometer. Koschara (7) purified the riboflavin solutions w ith chromatographic ad­

sorption and oxidation by permanganate, and determined concentrations directly in a stage photometer. Sullivan (13) measured the light absorption by the use of filters and a photo­

electric cell. Euler and Adler (3) and later Suppléé, Ans- bacher, Flanigan, and Hanford (14) and W hitnah, Kunerth, and Kramer (30) compared visually the fluorescence of un­

known and standard riboflavin solutions. Weisberg and Levin (19) described a similar method but used fluorescein solutions as standards. Cohen (2) measured the intensity of fluorescence directly with a photoelectric cell and ampli­

fier, using fluorescein as a standard.

The methods based on light absorption have the advantage th a t the absorption coefficients reported are in absolute units and can be determined very accurately. However, m any of the colored materials accompanying riboflavin interfere with the determination. Fluorescence measurements are more