I N D U S T R IA L aniENGINEEIUNG C H E M I S T R Y
ANALYTICAL EDITION
20,600 Copies of This Issue Printed
M arch 15,1939
Vol. 31, C onsecutive N o. 11
H a r r iso n E . H o w e , E d ito r
Vol. 11, N o. 3
An a l y t i c a l Me t h o d sf o r Me t h y l Br o m i d e...
. V. A. Stenger, S. A. Shrader, and A. W. Beshgetoor 121
Ph o t o c o l o r i m e t r ic De t e r m i n a t i o n o f St a r c h i n Pa p e r...L. E. Simerl and B. L. Browning 125
Ca r o t e n o i d s i n Ye l l o w Co r n . . . Loran 0 . Buxton 128
Vis c o m e t r i c De t e r m i n a t i o n o f Mo i s t u r e i n Ho n e y .
... F. C . Oppen and H . A. Schuette 130
Ra d i a t o r An t i f r e e z e Ma t e r i a l s...
... Harry Levin, Karl Uhrig, and Ervin Stehr 134
Vo l u m e t r i c De t e r m i n a t i o n o f Al u m i n u m Us i n g . So d iu m Ci t r a t e...
...Albert C. Titus and Melvin C. Cannon 137
Py c n o m e t r i c De t e r m i n a t i o n o f Le a d a s Su l f a t e . .
... W. Walker Russell and J. H. A. Harley, Jr. 140 J De t e r m i n a t i o no f Co l o ra n d Tu r b i d i t y i n So l u t i o n s
o f Gr a n u l a t e d Su g a r...A. R . Nees 142
Se l e c t i v e Ox i d a t i o n o f Le v u l o s e w i t h Po t a s s i u m Fe r r i c y a n i d e . . . . D . T . Englis and H. C . Becker 145
De t e r m i n i n g Ca r b o n Di o x i d e. Ra p i d Tu r b i d i m e t r i c Me t h o d . . . . Paul S . Roller and Guy Ervin, Jr. 150
Ef f e c to f Va r i o u s Pr e-e x t r a c t i o n s o n Li g n i n De t e r m i n a t i o n o f Wo o d ...
... Elwin E. Harris and R. L. Mitchell 153
A Sim p l e Hy d r o g e n El e c t r o d e Ou t f i t
W. Heinlen Hall 158
Io d o m e t r ic De t e r m i n a t i o n o f Co p p e r...
...William R. Crowell 159
Re c o v e r y o f Pl a t i n u m Us e d i n De t e r m i n a t i o n o f Po t a s h . . Margaret C. Swisher and Fred F. Hummel 162
As h De t e r m i n a t i o n i n Ce r e a l a n d Ot h e r Ve g e t a b l e Ma t e r i a l s... Charles H. Briggs 163
Mi n e r a l Oi l De t e r i o r a t i o n. A Re v i s e d Gr i g n a r d Ap p a r a t u s . . . . A . G . A s s a f a n d E. K. G la d d in g 164
Im p r o v e d Ga s An a l y s i s Ap p a r a t u s...
...C. M. Blair and J. H. Purse 166
Us e o f Si l ic a Co t t o ni n Fi l t e r Cr u c i b l e s...
... W. Walker Russell and J. H. A. Harley, Jr. 168
Si m p l i f i e d Co m b u s t i o n Pi p e t ...
. . . G. H. Nelson, H. D. Weihe, and D. F. J. Lynch 169
Fl a s kf o r Ef f i c i e n t St i r r i n g . . . A v e r y A . M o r t o n 170
Mi c r o c h e m i s t r y:
Mic r o d e t e r m i n a t i o n o f Fl u o r i n e b y Th o r i u m Nit r a t e Ti t r a t i o n... F . J. McClure 171
Mi c r o d e t e r m i n a t i o n o f Al k o x y l Gr o u p s...
...Adalbert Elek 174
No r t h e a s t e r n Un i v e r s i t y Ch e m i c a l La b o r a t o r i e s
...Arthur A. Vernon and Saverio Zuffanti 178
Te s t i n g De n t i f r i c e Ab r a s i v e s . . . Mervyn L. Smith 155
T h e A m erican C hem ical Society assum es no responsibility fo r th e sta te m e n ts a n d opinions ad v an ced b y co n trib u to rs to its pu b licatio n s.
P u b lic a t io n O ffice* E a * t o n , P a .
E d it o r ia l O ffic e : R o o m 7 0 6 , M i lls 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 is in g D e p a r t m e n t ! 3 32 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 io n a l 0 8 4 8 . C a b lex J ie c h e m ( W a s h in g t o n ) T e le p h o n e * B r y a n t 9 -4 4 3 0
P u b lish e d b y th e A m erican C h em ical Society, P u b lica tio n Office, 2 0 th &
N o rth a m p to n S ts., E a s to n , P a . E n te re d as second-class m a tte r a t th e P o st Office a t E a s to n , P a ., u n d e r th e A ct of M arch 3, 1879, as 48 tim es a y ear.
I n d u s tria l E d itio n m o n th ly on th e 1 st; A n a ly tic al E d itio n m o n th ly on th e 1 5 th ; N ew s E d itio n on th e 10th a n d 20 th . A cceptance fo r m ailing a t special r a te of p o stag e p ro v id ed fo r in S ectio n 1103, A ct of O ctober 3, 1917, a u th o riz e d J u ly 13, 1918.
A n n u a l su b sc rip tio n ra te s: 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 y c o m p l e t e $6.00; ( o ) In d u s t r i a l Ed i t i o n $3.00; ( 6 ) An a l y t i c a l Ed i t i o n
$2.50; (c) Ne w s Ed i t i o n$1.50; (a) a n d (6) to g e th e r, $5.00. F o reig n po stag e to co u n tries n o t in th e P a n A m erican U nion, $2.40, (a) $1.20; (6) $0.60; (c)
$0.60. C an a d ia n p o stag e o n e-th ird th e se ra te s. Single copies: (a) $0.75;
(b) $0.50; (c) $0.10. Special ra te s to m em bers.
N o claim s c an be allow ed fo r copies of jo u rn a ls lo st in th e m ails unless such claim s are received w ith in six ty d a y s of th e d a te of issue, a n d no claim s will be allow ed fo r issues lost as a re su lt of insufficient n o tice of change of address. (T en d a y s' ad v an ce n o tice req u ired .) “ M issing from hies"
can n o t be accep ted as th e reaso n fo r hono rin g a claim . C h arles L. P arso n s, B usiness M an ag er, M ills B uilding, W ash in g to n , D . C ., U . S. A.
INDUSTRIAL AND ENGINEERING CHEMISTRY
R A H W A Y , N. J .
R eagent chem icals in the hands o f skilled analysts play an im portant part in the production o f steel w hich m eets the high quality require
m ents o f m odern industry and en gineering. For the vital analysis and testin g necessary to ensure steel o f such quality, exacting chem ists use th e fo llo w in g M erck R eagent C hem icals, because lo n g experience has sh o w n that their purity and dependability are essential to uniform results.
R eagent E sch kas M ixtu re M erck to ta l S = .0 0 1 % m axim um . R eagen t A cid P e r c h lo r ic M erck
60% & 72% —S iO 2 = .0 0 0 m ax.
Reagent A cid M o ly b d ic M erck 85% —Free from co p p er.
R eagent A m m o n iu m P ersu lfate M e rc k —M n = .001% m ax.
R eagen t S odium B ism u th ate M e r c k —A ssays 85% N a B i 0 3 m in im u m .
Reagen t A m m o n iu m Sulfate M e rc k — P y rid in e free.
M erck M ineral A cids, Acid Phosphoric, and A m m on ia are in k eep in g w ith the h igh quality standards o f M erck R eagent C hem icals.
A catalog w i l l be sent on request
M E R C K & CO. I n c . tyllati
n ^ a c tu K Ù u j ( o f e m . i í t áNEW YORK PH IL A D E L P H IA S T . LO U IS IN C A N A D A : M E R C K St C O . L T D ., M O N T R E A L A N D T O R O N T O
MARCH 15, 1939 ANALYTICAL EDITION
T h is is a b o u t t h e p r e v e n t io n o f p y r o m e t r ic e r r o r s . . . I f y o u a re u s i n g C h r o m e l- A lu m e l C o u p le s , w e s u g g e s t y o u c h e c k - u p o n y o u r le a d w ir e . I t o u g h t t o b e m a d e o f C h r o m e l- A lu m e l, t o o , a n d h e r e ’s w h y : t h e s o - c a lle d
“ c o m p e n s a t i n g ” le a d s , t h a t a r e s o m e t i m e s u s e d , r e a lly c o m p e n s a t e o n ly ov er a n a r r o w lo w t e m p e r a t u r e r a n g e . T h e ir j u n c t i o n w it h t h e c o u p le in t h e c o u p le - h a n d le , fo r m s , in p r in c ip le , a n o t h e r t h e r m o - c o u p l e . A n d t h i s j u n c t i o n o f t e n g e t s v ery h o t , a s y o u k n o w , c r e a t in g a n E .M .F . t h a t c a u s e s a p lu s o r m i n u s erro r i n t e m p e r a t u r e r e a d in g s , o f f r e q u e n t ly a r o u n d 20° F . . . . Y o u a v o id t h i s c h a n c e o f e rro r b y u s i n g C h r o m e l- A lu m e l L e a d s a n d C h r o m e l- A lu m e l C o u p le s . F o r t h e w h o le s to r y , a sk fo r F o ld e r G Y . . . 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 t r o it , M ic h ig a n .
C H R O M E L - A L U M E L
L E A D S A N D C O U P L E S
6 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 11, NO. 3
c r
>ze.CLi-C
y l Æ e a â u t e t t i e n t â
a t clf-icjju.cil
cA t e d t l c e i
THE CENCO-DuNOUY
I n t e r f a c i a l T e n s i o m e t e r
A s i d e from the purely scientific relationship of surface and interfacial tension values to other phenomena of molecular attraction and the use of these measurements in the formation and establishment of physical laws involving molecular attraction, surface and interfacial tensions are im portant industrially in the control and improvement of numerous processes.
The ring method is an absolute method agreeing with theoretical calcu
lations within 0.25%. For colloidal solutions, where the tension values change rapidly, only the ring method can be employed with success.
70540 C e n c o -D u N o u y T e n s io m e t e r $175.00
For a Complete Survey of Ring M ethod Tension M easurements, Ask fo r Bulletin 101
CHICAGO 1700 Irving Pk. Blvd.
Lakeview S tation
S C I E N T I F I C INSTRUMENTS
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Cambridge A S tation
New York • Borton • C H IC A G O • Toronto • Los Angeles
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A complete line of Blue Line <HE> Flasks having ground stoppers is now obtain
able with ¥ grinding. These flasks pos- sess a ll the K im b le a d v a n ta g e s of retesting, annealing, Blue Line fused- in calibrations, and safe, convenient p ack ag in g that h ave a lre a d y estab lished the Blue Line as the standard.
For full particulars on specifications and prices, consult your dealer.
S T A N D A R D IZ E O N THE WHOLE K IM B LE L I N E . . . FOR A S S U R A N C E !
Stocked b y leading laboratory supply houses throughout the U.S. and Canada
• • • T h e V i s i b l e G u a r a n t e e o f I n v i s i b l e Q u a l i t y • • •
KIMBLE G L A S S C O M P A N Y • • • • v i n e l a n d , n . j .
n e w Y O R K • • C H I C A G O • - P H I L A D E L P H I A • • D E T R O I T - B O S T O N
MARCH 15, 1939 ANALYTICAL EDITION
8 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 11, NO. 3
grade o f Perchloric A c id that, m ade by this n e w process, is a better, pu rer Perchloric A c id than was fo rm er ly available for use in th e la boratory . . . and n o w obta in a b le th r o u g h B & A in q u a n titie s th a t m a k e its use
w i d e l y applicable to industrial processing!
B & A (A .C .S .) quality Perchloric A cid may be had in concentrations o f 7 0 % -7 2 % or low er. M ore specific inform ation on the use o f Baker and A dam son A.C.S.
Grade Perchloric A cid as applied to your particular re
quirem ents for an oxid izin g agent, or for any other uses you m ay have in m ind, may be had by w ritin g to the Baker and A dam son offices for a representative to call to discuss your problem .
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 “7 "> __i_
T V 7 T
B a k e r & A d a m s o n
D iv is io 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 Rec to r St., N e w Yor k L . r . f \ < U 4 S
A tla n t a • B a lt im o r e * B o s t o n • B u ffa lo • C a m d e n ( N . J . ) • C h a r lo t t e I N . C .) • C h ic a g o • C le v e la n d • D e n v e r * H o u s to n • K a n s a s C it y L o s A n g e le s • M ilw a u k e e • M in n e a p o lis • M o n te z u m a ( G a .) • P it ts b u r g h * P r o v id e n c e ( R . I.) • S a n F r a n c is c o • S t . L o u is • U tic a I N . Y .l W e n a t c h e e I W a sh . I • Y a k im a I W a s h .) • In 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 it e d • M o n tr e a l • T o ro n to • V a n c o u v e r
T o those w h o have lo n g know n Perchloric A cid only as a laboratory chem ical, a carload o f Perchloric is a startlin g realization . . . but on e that is n ow entirely feasible for Baker and A dam son.
Today, Baker and A dam son is prepared to ship you as m uch as you w ant— an ounce b ottle, a carboy— or even a carload!
Perhaps even m ore am azing, how ever, is the radical price reduction that has accom panied the introduction o f this new , exclusive process for m anufacturing this p ow erful oxid izin g agent.
. . . M o r e th an a 9 0 % re d u c tio n in th e cost o f a
MARCH 15, 1939 ANALYTICAL EDITION 9
Determine Titanium and Zirconium with Newest MALLINCKRODT Analytical Reagent A C ID P A R A - H Y D R O X Y - P H E N Y L A R S O N I Q
Simpson and Chandlee* describe a new method for effectively separating titanium and zirco
nium from other commonly occurring ions by means of a single precipitation. The reagent used was Mallinckrodt Acid Para-Hydroxy-Phenylarsonic, A.R. This newest addition to the Mallinckrodt Analytical Reagent family is designed according to specifications for this analytical procedure, and is ready for use as received.
Send for descriptive literature on this new chemical and for the Mallinckrodt Catalog of Analytical Reagents and Laboratory Chemicals, which shows the predetermined maximum limits of impurities for nearly 500 chemicals and reagents.
• S im p so n , C. T . a n d C handlee, G. C ., In d . and Eng. Chent., A n a l. E d., 10:042, N ov. 15, 1938.
C H E M IC A L WORKS
ST. LOUIS NEW Y O R K TORONTO
CH ICAGO P H IL A D E L P H IA M O NTR EA L
10 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 11, NO. 3
NEW, IN T E R M E D IA T E M O D EL
4276-M
FOR T H E RA PID M IL L IN G O F HOMOGENEOUS S A M P L E S O F A G R E A T V A R I E T Y O F C O M M E R C IA L M A T E R IA L S FO R
L A B O R A T O R Y A N A L Y S IS
WILEY LABORATORY MILL, Intermediate Model. A rugged, com
pact, motor driven modification of the F.R.I.-Micro Model (as described on page 278 of our catalogue), suggested by the U. S. Bureau of Plant Industry for the rapid milling of larger homogeneous samples than are obtainable with the Micro Model.
Chamber of the new model is 40 mm diameter x 22 mm deep, with two stationary knives and rotor with four cutting edges. The latter revolves at high speed, producing a shearing action which prevents loss of moisture from heat. A 20 gram, 40 mesh sample of dried plant stem tissue can be
E
repared in 15 to 20 minutes; or a similar sample of J^-inch pieces of soy- ean stems in 5 to 7 minutes.A removable glass plate forms the face of the chamber and permits ob
servation during operation, with easy access for cleaning. Five speeds from 897 to 3800 r.p.m. are available. Samples are collected in either 4 oz.
jars or in small receivers attached to delivery tubes with sieve tops. Over
all dimensions 13% x 11 inches x 11 % inches high.
4276-M . W iley L ab o rato ry M ill, In te rm e d ia te M o d el, as a b o v e described, oom plete w ith th re e d eliv ery tu b e s w ith sieve to p s 20, 40 a n d 00 m esh, respectively, each w ith receiver, tw o e x tra s ta tio n a ry k nives, etc., a n d d irectio n s for use.
W ith m o to r for 110 v o lts, 60 cycles, a. o ...$160.00 C ode W o rd ... Elobx
Show ing sam ples of som e m a te ria ls successfully g ro u n d in th e new In te rm e d ia te M odel W iley L a b o ra to ry M ill
Samples may be sent to us for determination as to the suitability of the Wiley Mill for preparing any specific material for laboratory analysis. If found suitable, we will return, without charge, a milled sample with report as to time required for milling, size of sieve opening through which it passed, and other pertinent details of the test.
Copy o f p a m p h le t EE-107, con ta in in g m ore d eta ile d d escrip tio n a n d listin g o th e r m o d e ls o f th e W iley M ill, s e n t upon requ est.
ARTHUR H. T H O M A S COMPANY
R E T A IL —W H O LE SA LE— E X P O R T
LA BO RATO RY APPARATUS A N D REAGENTS
W E S T W ASHINGTON S Q U A R E P H IL A D E L P H IA , U.S.A.
Cable Address, "B alance,” Philadelphia
INDUSTRIAL »»a ENGINEERING CHEMISTRY
ANALYTICAL EDITION ♦ H a rriso n E. H o w e , E ditor
A nalytical M ethods for M ethyl B rom ide
V. A. STENGER, S. A. SHRADER, A N D A. W. BESHGETOOR T he Dow Chemical Company, M idland, M ich.
M e th o d s are p r e s e n te d fo r d e te r m in in g m e t h y l b r o m id e in a ir a n d in p r o d u c ts for w h ic h i t is u s e d as a f u m ig a n t . T h e B e il- s t e in t e s t m a d e w it h a c o m m e r c ia l m e t h a n o l to r c h serves fo r ra p id d e t e c t io n , a n d w it h a r tific ia l sta n d a r d s m a y b e e m p lo y e d fo r s e m iq u a n t it a t iv e e s t im a t io n in th e r a n g e 50 t o 500 p . p . m . M ore a c c u r a te r e s u lts are o b ta in e d b y m e a n s o f e th a n o l - a m in e h y d r o ly sis a n d b r o m id e d e te r m i
n a t io n . T h e K o lth o ff-Y u tz y p r o c e d u r e is u se d fo r a m o u n t s in t h e a b o v e r a n g e , a n d t h e V o lh a rd t it r a t io n for g r e a te r c o n c e n tr a tio n s . F o r t h e a n a ly s is o f f u m ig a t e d p r o d u c t s , t h e K o lth o fT -Y u tzy m e t h o d is a p p lie d a fte r a s h in g w it h a lc o h o lic p o t a s s iu m h y d roxid e i n t h e p r e se n c e o f s o d iu m c h lo r id e . R ec o v eries avera g e 96 p er c e n t o n k n o w n s w it h 1 m g . o f b r o m id e p er 10 g r a m s o f flo u r , n u t s , d ried fr u it s , or to b a c c o .
S
INCE the recent introduction of a pure grade of methyl bromide in commercial quantities, this compound has found increasing application, particularly as a fumigant (.2, 9). In the course of research on it at the Dow Laboratories, several analytical problems have arisen; as progress toward the solution of these may be of general interest, re
sults accumulated during the past two years are summarized here. The problems studied deal with the determination of methyl bromide in fumigated products and in air, both at fumigating concentrations and at greater dilution.
H a n d lin g o f M e th y l B r o m id e
Precautions in handling methyl bromide are necessary, since the vapors are toxic if inhaled in excessive amounts.
Prolonged exposure to low concentrations should also be avoided. Operations with open containers should be carried on only in a thoroughly ventilated place. For preparing small samples the procedure is as follows:
Soft-glass bulbs are blown from finely drawn tubing and bent as shown in Figure 1, A. The volume of the bulb should not ex
ceed too greatly that of the sample desired, in order that air buoyancy corrections may be kept low. A supply cylinder of commercial methyl bromide (99.7 per cent pure by bromine as
say) is kept in an efficient hood. Liquid from the cylinder is transferred to a small test tube ( 1 X 5 cm.) surrounded by lumps of solid carbon dioxide. The tip of a tared sample bulb is dipped into the methyl bromide and the bulb quickly cooled in an ace
tone-solid carbon dioxide bath. Intermittent wanning and cool
ing serve nearly to fill the bulb if desired; or by inverting, some liquid may be blown out to obtain a smaller sample. The tip is sealed off while the bulb is again cooled, then placed under a beaker to reach room temperature before reweighing. From a number of such samples, the desired weights can be selected for use in small fumigation test chambers.
D e t e c t io n i n A ir
For the protection of those working with methyl bromide, it is important to have a simple procedure capable of indicat
ing quickly the presence of dangerous concentrations. The well-known Beilstein test for organic halide vapors is satis
factory. All that is necessary is a flame impinging on a copper strip; in the presence of methyl bromide or other halide vapor, the flame becomes green or blue. Obviously the fuel supply should be kept free from halogen.
Ta b l e I. De t e c t i o n o f Me t h y l Br o m i d e w i t h La m p M eth y l
B rom ide M onobrom obenzene
P re s e n t“ F lam e Color 20° C. 30° C.
P . p. m. M l . / 100 ml. m ineral o
0 A lm ost invisible 0 0
50 F a in t green 0 .9 0 .5
100 M o d erate green 1 .8 0 .9
200 S tro n g green w ith tra c e of blue 3 .5 1 .8
500 Blue-green 8 .5 4 .3
1000 S tro n g blue 1 7 .0 8 .5
° C o n cen tratio n s expressed in p a rts p er m illion b y volum e h av e b een calcu>
lated fo r 760 m m . of m ercury a n d 25* C ., assum ing th e id eal gas law to be valid.
A commercial methanol torch appeared most practical for general use. The one selected is a self-generating burner which had been designed for detection of halide refrigerant leaks and is equipped with a sampling tube and copper cone.
(This torch, known as the Frigidaire halide leak detector, SA-2136, is available at a nominal price from the Frigidaire Division, General Motors Sales Corp., Detroit, Mich.) The sensitivity varies with different rates of combustion, maximum sensitivity being obtained with a low flame. This is some
what too delicate for the purpose; hence the valve is ad
justed arbitrarily so that with pure air the inner flame just disappears within the copper cone. Under these conditions the outer flame exhibits colors as showTi in Table I, when air containing methyl bromide enters the sampling tube.
As comparison standards for indicating the appearance of the flame at various concentrations, solutions of monobromo- benzene in clear heavy paraffin oil are useful. To 100-ml.
121
122 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 11, NO. 3 portions of the oil are added the volumes of bromobenzene
shown in Table I. The solutions are kept in containers of at least 500-ml. capacity and should be shaken well before use.
The vapor pressure of bromobenzene above each solution at the given temperature is such that when the sampling tube is inserted, the flame assumes the characteristics shown by the corresponding methyl bromide-air mixture.
Contamination of the sampling tube m ust be avoided, and opportunity allowed for copper bromide to burn out of the torch between analyses. Naturally the air drawn through standards should be free from m ethyl bromide. Light con
ditions under which samples and standards are observed should be as nearly identical as possible.
With a torch operating, the approximate concentration of m ethyl bromide in air can be told at a glance. A strong green flame tinged with blue is evidence of an unsafe con
centration. The method has been useful in this laboratory for detecting cylinder leakage, roughly checking diffusion rates, and following the aeration of fumigated products.
Other volatile organic halides also respond to this test, which is not specific for m ethyl bromide.
D e t e r m in a t io n in A ir
For a more exact determination of methyl bromide at fumigating concentrations (16 to 48 mg. per liter; 1 to 3 pounds per 1,000 cubic feet), methods based on hydrolysis and subsequent halogen determination offer the easiest attack. In early experiments alcoholic potassium hydroxide was employed in a refluxing apparatus, the liberated bromide being titrated argentometrically. Busbey and Drake (1) modified this method by applying an iodometric bromide determination (8), giving the advantages of greater sensitivity and specificity. Unfortunately the hydrolysis is slow and the apparatus cumbersome.
Rauscher (11) has recently described the use of mono- ethanolamine in halogen determinations. Trial of this re
agent revealed that methyl bromide decomposes in it faster than in alcoholic alkalies. For practical purposes the reac
tion is complete after 15 minutes at room temperature, making possible a simple procedure. It is necessary only to take the sample, expose to ethanolamine, and determine bromide by the Volhard method (4) or by Kolthoff and Y utzy’s modifica
tion (£?) of van der Meulen’s method (10). The former is more rapid, while the latter requires elimination of the etha
nolamine but is more sensitive and specific, since chlorides do not interfere. In practice, the Volhard method is used for samples containing more than 5 mg. of m ethyl bromide, and the Kolthoff-Yutzy procedure is employed for smaller amounts.
An air-sampling device capable of allowing exposure to ethanolamine is necessary. The authors have used evacuated 2-liter flasks, through the stopcock of which 3 ml. of reagent m ay be introduced after sampling. A T 29/42 joint be
tween flask and stopcock provides for easy removal of the hydrolyzed sample. The commercial lubricant Lubriseal is satisfactory for the stopcock, but only ethanolamine should be placed on the glass joint, especially if the Kolthoff-Yutzy method is to be employed. For sampling without vacuum apparatus, calibrated wide-mouthed glass-stoppered bottles of about 1-liter capacity are useful. Samples are introduced by placing the bottles within the chamber to be tested and pumping with a plunger, shown in Figure 1, B and C. The plunger is made from brass tubing and a rubber sheet about 2 mm. thick, slightly smaller in diameter than the bottle.
Slits in the rubber permit easy entrance through the bottle neck, while a section of a rubber stopper on the tube end prevents breakage. About 20 strokes serve to change the air completely; then a sealed soft-glass bulb containing 2 ml.
of ethanolamine is introduced, the stopper inserted, and the bulb broken by shaking. After 15 minutes or longer for hydrolysis, either halogen method may be applied.
Vo l h a r d Me t h o d. The stopper and sides of the apparatus are washed down with about 30 ml. of water, and a measured amount of standard silver nitrate (0.02 or 0.1 ¿V, depending on the amount of bromide expected) is introduced, with enough 6 N nitric acid to provide a 1- to 3-ml. excess. At this point silver bromide precipitates if methyl bromide was present in the sample.
The excess silver nitrate is titrated with standard 0.02 or 0.1 N thiocyanate, using the customary ferric alum indicator (4). A blank on the same amount of ethanolamine should be carried through the procedure and allowed for in calculating the results, since ethanolamine slightly retards the end point. Ethanol
amine also sensitizes silver bromide to the action of light, which should be avoided as much as possible. Dark precipitates may be filtered off before back-titration. One milliliter of 0.100 N silver nitrate is equivalent to 9.50 mg. of methyl bromide.
M g. of C H sB r p e r lite r X 0.0625 *= p o unds p er 1000 cubic feet.
M g. of CH aB r p e r lite r X 258 = p a rts p er m illion (calcu lated fo r 760 m m . a n d 25° C.)
This procedure was tested in two ways: (1) B y means of heavy glass rod inserted through a rubber stopper, a methyl bromide sample bulb was crushed within a bottle, after which an ethanolamine bulb was broken by shaking; (2) a steel drum of 118-liter capacity, fitted with a bulb-breaking device and small electric fan, was sampled directly by the methods in
dicated. The former procedure was used to check the com
pleteness of hydrolysis, with results as shown in Table II.
The latter includes sampling errors and corresponds more closely to actual practice. In this case, usually one or more open bottles were placed inside the drum before each run, and another sample was taken through a tube leading to the evacuated flask. These data are included in Table III.
Ko l t h o f f- Yu t z y Me t h o d. All ethanolamine m ust be removed prior to the bromide determination; otherwise organic bromides are formed, causing low results. A ttem pts
S O F T G L A S S
B R A S S RUBBER
Fi g u r e 1. Bu l b a n d Pl u n g e r
MARCH 15, 1939 ANALYTICAL EDITION 123
Ta b l e II. Bo t t l e Ex p e r i m e n t s, Vo l h a r d Me t h o d
B o ttle C IIaB r C H jB r
Volum e T a k e n F o u n d E rro r
M l. M g. Mg. Mg. %
515 5 .6 5 .6 0 .0 0 .0
1026 2 0 .3 2 0 .2 - 0 . 1 - 0 . 5
515 2 3 .3 2 3 .2 - 0 . 1 - 0 . 4
515 3 8 .0 3 8 .0 0 .0 0 .0
515° 5 3 .6 5 3 .2 - 0 . 4 - 0 . 8
1030 199.0 197.8 - 1 . 2 - 0 . 6
° 10-m inute hy d ro ly sis; all o th ers allowed 15 m inutes.
Ta b l e I Dr u m Ex p e r i m e n t s, Vo l h a r d Me t h o d C H 3B r Sam pling H ydrolysis C H jB r
T ak en M eth o d Tim e F o u n d E rro r
M g ./l. M in . M g ./l. M g ./l. %
1 0 .8 1-1. b o ttle 30 10.7 - 0 . 1 - 0 . 9
10 .8 2-1. flask 30 10 .8 0 0
16.1 1-1. b o ttle 15 16 .0 - 0 . 1 - 0 . 6
19 .9 1-1. b o ttle 15 19.9 0 0
19.9 2-1. flask 25 19 .8 - 0 . 1 - 0 . 5
2 1 .3 1-1. b o ttle 15 2 1 .4 4 -0 .1 + 0 . 5
2 1 .3 2-1. flask 20 2 0 .8 - 0 . 5 - 2 . 4
2 3 .8 1-1. b o ttle 15 2 3 .5 - 0 . 3 - 1 . 3
at simple evaporation failed because of oxidation of some ethanolamine to nonvolatile and brominatable compounds.
This oxidation takes place more rapidly at higher tempera
ture« and in more alkaline solutions. The procedure found most reliable consists in adding sodium bicarbonate to hold bromide, boiling off most of the water, then rapidly expelling the iemaining water and ethanolamine by heating in a cur
rent of steam. The steam displaces oxygen and aids in sweeping out vapors. A well-ventilated hood is necessary to remove the dense fumes of ethanolamine. B y the use of an e>it tube and condenser these m ay be avoided, but the operation is then much slower. Mechanical losses by bump
ing m ust be guarded against; the addition of a little sodium chloride lowers the magnitude of such losses, although in
creasing the tendency to bump. Bumping may be reduced by heating flasks from the sides instead of the bottom, as dryness approaches.
Reagents. Ethanolamine. The chief requirement is that no organic residue be left after evaporation in steam as above.
Fresh products from the Eastman Kodak Company have been satisfactory, but on standing yellow oxidation compounds some
times formed and were removed by distillation in a nitrogen at
mosphere.
Sodium chloride, a saturated solution of the c. p. product.
Sodium bicarbonate, c. p. powder.
Sodium acid phosphate, c. p. NaH2P0<.H20 crystals.
Hypochlorite solution, 1 N sodium or potassium hypochlorite in 0.1 N sodium or potassium hydroxide (6,10).
Sodium formate, 50 grams of c. p. sodium formate in water to make 100 ml.
Sodium thiosulfate, 0.01 N solution stabilized with 1 gram of sodium carbonate per liter. Standardized against 0.01 A potas
sium iodate using 75 ml. of water, 10 ml. of G N sulfuric acid, and 0.5 gram of pure potassium iodide.
Sodium molybdate, 1 gram per 100 ml.
Potassium iodide, c. p. crystals.
Starch indicator, prepared according to Iiolthoff (5).
Sulfuric acid, 6 A’.
Procedure. The hydrolyzed sample is washed into a 250-ml.
Erlenmeyer flask and treated with 0.5 ml. of saturated sodium chloride solution and approximately 0.5 gram of sodium bicar
bonate. By evaporation over a flame or on a hot plate the volume is reduced to not less than 10 ml.; then the evaporation is quickly continued to dryness by heating while steam is blown through the flask. Constant swirling is necessary to prevent bumping, and at the end all ethanolamine must be driven from the sides of the flask. With the steam off, the flask is allowed to cool; then it is steamed again without external heating until the salt redissolves. The steam tube is rinsed with water and the volume brought to about 50 ml.
To the solution are added 2.5 ml. more of the saturated so
dium chloride, about 1 gram of sodium acid phosphate, and
2 ml. of hypochlorite, and the mixture is heated to boiling. After a minute or so, 2 ml. of formate solution are introduced and boil
ing is continued for 2 minutes. The sample is cooled, diluted to 75 ml., and treated with one drop of molybdate solution, 0.5 gram of potassium iodide, and 10 ml. of G N sulfuric acid. Ti
tration should be made immediately with standard thiosulfate, starch indicator being added just before the end point. A blank on ethanolamine with all other reagents should be carried through the entire procedure and subtracted. One milliliter of 0.010 iV thiosulfate is equivalent to 0.1583 mg. of methyl bromide.
Drum tests of this procedure are listed in Table IV. The data reveal bromide losses which are small in actual amount, but relatively large in percentage. Fortunately, in this range (50 to 500 p. p. m.) absolute accuracy is rarely neces
sary. Experiments on evaporating ethanolamine with known amounts of potassium bromide indicate that most of the error lies in this step, and may be due both to mechanical loss and to residual traces of organic matter. Other amines which can be evaporated without decomposition were stud
ied, but none was as efficient in its hydrolyzing action as ethanolamine. Likewise, other buffers than sodium bicar
bonate were tried for binding the bromide, without success in improving the method. If more accurate results are neces- sarj', one may obtain corrections for bromide losses by carry
ing out the evaporation procedure with known inorganic bromides and ethanolamine.
Ta b l e IV. Dr u m Ex p e r i m e n t s, Ko l t h o f f- Yu t z y Me t h o d C H jB r Sam pling H y drolysis C H jB r
T ak en M eth o d Tim e F o u n d E rro r
M g ./l. M in . M g ./l. M g ./l. %
0 .2 1 8 1-1. b o ttle 20 0 .1 9 8 - 0 . 0 2 0 - 9 . 2
0 .2 1 8 2-1. flask 20 0 .1 8 9 - 0 . 0 2 9 - 1 3 . 3
0.381 1-1. b o ttle 20 0 .3 7 4 - 0 . 0 0 7 - 1 . 9
0.381 2-1. flask 20 0 .3 7 9 - 0 . 0 0 2 - 0 . 5
0 .8 5 5 1-1. b o ttle 15 0 .7 9 8 - 0 . 0 5 7 - 6 . 7
0 .8 5 5 1-1. b o ttle 20 0 .8 1 9 - 0 . 0 3 6 - 4 . 2
0 .8 5 5 2-1. flask 20 0.8 2 1 - 0 . 0 3 4 - 4 . 0
1.139 1-1. b o ttle 15 1.104 - 0 . 0 3 5 - 3 . 1
1.139 1-1. b o ttle 20 1.111 - 0 . 0 2 8 - 2 . 5
1.139 2-1. flask 20 1.113 - 0 . 0 2 6 - 2 . 3
1.661 1-1. b o ttle 15 1.618 - 0 . 0 4 3 - 2 . 6
1.661 1-1. b o ttle 20 1.611 - 0 . 0 5 0 - 3 . 0
1.661 2-1. flask 20 1.609 - 0 . 0 5 2 - 3 . 1
D e te r m in a tio n o f B r o m id e in F u m ig a te d P r o d u c ts During fumigation with methyl bromide, most products absorb minute amounts of bromine. There is evidence that the greater part of this exists in the form of inorganic bromide, rather than as dissolved or adsorbed methyl bromide. Studies are being conducted to ascertain the state of all this bromine;
meanwhile it is important to have a method for determining the total held by various products, especially by foodstuffs.
Several procedures tried indicated that ashing with alcoholic potassium hydroxide is the most promising for securing all bromine free from organic matter. Details presented here were chosen with the aim of making the method applicable to materials of widely varying character.
Since nearly all natural products contain considerable chloride, the method chosen must be capable of determining bromide in its presence. The Kolthoff-Yutzy procedure (6) fulfills this condition and provides the sensitivity required for the small amounts involved. The fact that iodine be
haves in the same manner as bromine is of no consequence, since only traces are likely to be present and the principal object is to measure increases in bromide content resulting from fumigation. This purpose is served by the use of un
fumigated controls which are analyzed along with the fu
migated samples, the difference being due to bromine gained through exposure to methyl bromide.
Re a g e n t s required arc the same as those listed above, omit
ting ethanolamine and sodium bicarbonate, and adding alcoholic
124 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 11, NO. 3
Ta b l e V . De t e r m i n a t i o n o f Br o m i n e i n Va r i o u s Pr o d u c t s F o u n d
C o rrected
Sam ple B r
A dded B r
F o u n d for
B lan k E r ro r
Mg. M g . M ç . M g. %
D ried raisins 0
0 .9 7 4 0 .9 7 4 0 .9 7 4
0 .0 6 8 1 .0 1 8 0 .9 9 9 0 .9 8 9
0^950 0.9 3 1 0 .9 2 1
—Ô.Ô24 - 0 . 0 4 3 - 0 . 0 5 3
- 2 .5 - 4 . 4 - 5 . 4
W hole-w heat flour 0
0 .9 7 4 0 .9 7 4 0 .9 7 4
0 .0 9 0 1.0 4 0 1.0 7 4 1.054
0 .9 5 0 0 .9 8 4 0 .9 6 4
-Ô.*024 + 0 .0 1 0 - 0 . 0 1 0
- 2 . 5 + 1 .0 - 1 . 0 P e c an n u t m e a ts (u n salted ) 0
0 .9 7 4 0.9 7 4 1 .9 4 8
0 .0 4 5 0 .9 8 3 0 .9 8 3 2 .0 0 0
0 .9 3 8 0 .9 3 8 1.955
—Ô * 036
—0 .0 3 6 + 0 .0 0 7
—3 .7 - 3 . 7 + 0 . 4
D rie d peaches 0
0 .9 7 4 0 .9 7 4 0 .9 7 4
0 .1 0 7 1.106 1.0 3 8 1.033
o!999 0.9 3 1 0 .9 2 6
+CLÔ25 - 0 . 0 4 3 - 0 . 0 4 8
+ 2 ‘.6 - 4 . 4 - 4 . 9
A m erican cheese 0
0 .9 7 4 0 .9 7 4 0 .9 7 4
0.0 5 3 0 .9 9 9 0 .9 8 0 0 .9 9 2
o!946 0 .9 2 7 0 .9 3 9
-Ô !Ô 28 - 0 . 0 4 7 - 0 . 0 3 5
- 2 . 9 - 4 . 8 - 3 . 6 T o b acco 0 (cured lig h t b u r-
ley)
0 0 .9 7 4 0 .9 7 4 0.9 7 4
0 .1 9 6 1.128 1.1 1 8 1.1 4 4
0 .9 3 2 0 .9 2 2 0 .9 4 8
—Ô.042 - 0 . 0 5 2 - 0 . 0 2 6
- 4 ! 3 - 5 . 3 - 2 . 7 ft F o r to b acco th e sam ples were 5 g ram s; fo r all o th ers, 10 gram s.
potassium hydroxide, 2 grams per 100 ml. of 95 per cent ethyl alcohol; potassium fluoride, c. p. KF.2H20 crystals; hydrochlo
ric acid, about 0.2 N (1 to 50); and sodium hydroxide, 2 grams per 100 ml.
For containing the samples during ashing, silica dishes are to be preferred. Those used in this laboratory are 8 cm. in diame
ter and 2.5 cm. deep, with flat bottoms. Glassware may be used but has much shorter life; platinum dishes are satisfactory. The muffle used for ashing should be provided with temperature con
trols. Provision for introducing a slow stream of oxygen during ignition is also desirable, as it reduces the time required for com
plete combustion.
Pr o c e d u r e. An appropriate sample (5 to 10 grams), ground if necessary to ensure uniformity, is weighed out in a silica dish and treated with 3 ml. of saturated sodium chloride and 40 ml. of alcoholic potassium hydroxide, evenly distributed. After evapo
ration of the alcohol, preferably on a steam bath, the sample is dried for a short time at 110° C., then ashed in a muffle at 400° C.
The large amount of smoke evolved may be diminished by ignit
ing occasionally with small pieces of burning filter paper. Care should be taken that the temperature at no time exceeds 500° C., and a bright local glowing of carbon should be avoided, although dull glowing is desirable. When no more flames appear, the muffle is brought to 500° C. and the dish allowed to remain at this temperature for 10 minutes.
Upon cooling, the residue is extracted with two 25-ml. portions of dilute hydrochloric acid (1 to 50), except in the case of tobacco samples, for which only water should be used. The extracts are filtered through coarse paper, residue and paper being washed with three 10-ml. portions of water and the filtrates caught in a 250-ml. wide-mouthed Erlenmeyer flask. The filter paper is returned to the dish and again treated with 3 ml. of salt solution and 10 ml. of alcoholic potassium hydroxide. Drying and igni
tion are repeated as before, and the residue is extracted with 25 ml. of dilute hydrochloric acid and three 10-ml. portions of water, catching the filtrate in the same flask as before. In the case of tobacco, water is substituted for acid in this extraction also.
The combined filtrates are neutralized with sodium hydroxide solution, adjusting to the color change of methyl orange, and are evaporated to about 75 ml. The Kolthoff-Yutzy method is followed as outlined above, beginning with the addition of phos
phate. No further introduction of sodium chloride is necessary.
Prior to acidification about 0.5 gram of potassium fluoride is added to combine with any iron present. One milliliter of 0.010 N thiosulfate is equivalent to 0.1332 mg. of bromide ion.
A blank on the reagents should be subtracted if absolute values are desired, but this is not necessary if only the gain due to fumi
gation is to be determined.
The ashing procedure recommended is the result of nu
merous experiments designed to obtain the m ost consistent recoveries. The method outlined is capable of recovering 94 per cent or more of added bromides, in amounts of a few milligrams. Addition of salt helps to prevent mechanical and volatilization losses of bromide, and also seems to favor
complete extraction of the ash. Prior to its use, recoveries were much lower, especially in the case of tobacco, from which sometimes 30 per cent m ight be lost. In case hy
drochloric acid is used in extracting tobacco ash, results are erratic, probably owing to interference of inorganic materials in the Kolthoff-Yutzy method. End points, normally good, exhibit pronounced return of iodine color under these con
ditions. Probably the same would hold true with any high- ash high-nitrogen product.
For a more rapid approximate procedure, the second ashing may be omitted and only the first filtrate analyzed for bro
mide. The second filtrate contains roughly 10 per cent of the total, but this figure may vary considerably. I t is best to make the second ignition and extraction even though more time is required. In several tests in which a third ashing was made, the bromine found was negligible, indicating that losses other than incomplete extraction account for errors in the procedure.
Table V shows the recovery of known amounts of potassium bromide added to 10-gram samples of several products (5-gram samples in the case of tobacco). A reagent blank of 0.014 mg. of bromine has been deducted. The data in Table VI were obtained during typical fumigation experi
ments. They have no significance as tests of the procedure, since all were run as unknowns, but are of interest in showing the magnitude of bromine absorption. The amount of bro
mide gained during fumigation varies considerably with m ethyl bromide concentration and time of exposure. Also, it has been noted that unfumigated samples from different sources show variations in their bromine content. Appar
ently determinations of bromide have not previously been made on several of the products reported here. Leipert (7) gave a. comprehensive literature review without mentioning analyses of any of them. Geddes and Lehberg (3) recently published a method applicable to water-soluble bromine in brominated flours. They reported recoveries of 93 to 97 per cent but did not mention the bromine content of untreated samples. While the results for untreated products listed in Table VI m ay be slightly high, owing to traces of iodine, they probably indicate approximately the percentages of bromine to be expected in average unfumigated material.
Ta b l e V I . De t e r m i n a t i o n o f Br o m i n e i n Fu m i g a t e d Pr o d u c t s
U n fu m ig ated F u m ig ate d G ain D u e to
Sam ple C o n tro ls Sam ples F u m ig atio n
% % %
D ried raisins 0 .0 0 0 7 0 .0 0 1 0 0 .0 0 0 3
W h o le-w h eat flour 0 .0 0 0 9 0 .0 1 0 0 0 .0 0 9 1
P e c an n u t m eats 0.0 0 0 4 0 .0 1 9 9 0.0 1 9 5
D ried peaches 0.0011 0 .0 0 3 0 0.0 0 1 9
A m erican cheese 0.0 0 0 5 0 .0 0 8 0 0.0 0 7 5
C u red to b acco 0.0 0 3 9 0 .0 1 0 4 0 .0 0 6 5
L ite r a tu r e C ite d
(1) Busbey, R . L., and D rake, N . L., I n d . Eno. C h e m ., A nal. E d ., 10, 390 (1938).
(2) Dow Chemical Co., M idland, M ich., “ M ethyl B rom ide," 1937.
(3) Geddes, W . F., and Lehberg, F. H „ Cereal Chem., 15, 49 (1938).
(4) H illebrand, W . F., and Lundell, G. E . F ., "A pplied Inorganic Analysis," p. 589, New Y ork, John W iley & Sons, 1929.
(5) Kolthoff, I. M., and F urm an, N. H., “ V olum etric Analysis,” Vol.
11, p. 349, New Y ork, Jo h n W iley & Sons, 1929.
(6) Kolthoff, I . M ., and Y utzy, H . C ., I n d . En o. C h e m ., Anal. E d.
9, 75 (1937).
(7) L eipert, T ., Alikrochim. Acta,3, 147 (1938).
(8) L eipert, T ., and W atzlawek, O., Z . anal. Chem. 98, 113 (1934).
(9) M ackie, D. B., and C arter, W . B., Calif. D ept. Agr., B ull. 26, 153 (1937).
(10) Meulen, J . H ., van der, Chem. Weekblad, 28, 82 (1931).
(11) R auscher, W. H ., Ind. Eno. C h e m ., Anal. E d ., 9, 296 (1937).
R e c e i v e d November 4 , 1938. Presented before the Division of Physical and Inorganic Chemistry at the 96th Meeting of the American Chemical Society, Milwaukee, Wis., September 5 to 9, 1938.
