Industrial and Engineering Chemistry : analytical edition, Vol. 18, No. 5

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

A N A L Y T I C A L E D I T I O N

V O LU M E 18, N U M B E R 5 ISSUED M A Y 23, 1946 C O N S EC U T IV E N U M B E R 10

Assistant to Editor: N . A . P A R K IN S O N

Manuscript Editing: G . G L A D Y S G O R D O N

R. P. C H A P M A N J . R. C H U R C H IL L B. L . C L A R K E

E D IT O R : W A L T E R J. M U R P H Y Associate Editor: L A W R E N C E T . H A L L E T T

A ssistant Editors

Manuscript Reviewing: S T E L L A A N D E R S O N

A d viso ry Board

Contributing Editor: R. H . M U L L E R

Make-up: C H A R L O T T E C . SAYRE

I

T . R. C U N N I N G H A M G . E . F. L U N D E L L M . G . M E L L O N

R. H . M U L L E R B. L . O S E R . H . H . W IL L A R D

\ £ tX js **spBbftr

Editorial...279 Improvement of Precision by Repeated Measurements . .

John Mandel 280 Determining Rates of Deoxidation of Iron O x id e Materials

in Reducing G ases . . . E. P. Barrett and C . E. Wood 285 Estimation of Naphthalene in Absorbing O i l ...

P. E. Reichardt and D. L. White 286 Determination of Vitamin A in Liver ...

W illis D. G allup and J . A . Hoefer 288 Determination of Uronic A c i d s ...

R. M . M cCready, H . A . Swenson, and W . D. Maclay 290 Routine A nalysis of Manganese B r o n z e ...

Edwin K. Babson and Wayne W . Johnson 292 Determination of Small Amounts of Arom atic Hydrocarbons

in Aqueous S o lu tio n s ...

H . E. M orris, R. B. Stiles, and W . H . Lane 294 Determination of Solubility of Styrene in Water and of Water

in S t y r e n e ...W . H . Lane 295 Excessively High Riboflavin Retention during Braising of

B e e f ...Winifred F. Hinman, Ruth E. Tucker, Loretta M , Jans, and Evelyn G . Halliday 296 Conductometric Titrations with Organic R eag en ts...

J . F. C o rw in and fd. V . M oyer 302 Determination of Tetraethyllead in Gasoline by X-Ray

Absorption . M iles V . Sullivan and Herbert Friedman 304

M IC R O C H E M IS T R Y

Phenolic Resin G lu e Line as Found in Yellow Birch P ly­

wood . . C . A . Farrow, D. H . Hamly, and E. A . Smith 307 X-Ray Identification and Crystallography of A ld ehyd es

and Ketones as 2,4-Dinitrophenyihydrazones . . . . George L. Clark, W ilbur I. Kaye, and Thomas D. Parks 310 Determination of M ethyl Chloride in A i r ...

J . L. Franklin, E. L. G unn, and R. L. Martin 314 Field Test for Surface D D T ...

Henry A . Stiff, J r ., and Julio C . Castillo 316 Colorimetric Determination of Fatty A c id s and Esters . .

Uno T. H ill 317

Determination of Nitrogen, Phosphorus, Potassium, Cal­

cium, and Magnesium in Plant T is s u e ...

Omer J . Kelley, A lbert S. Hunter, and Athan J . Sterges 319 Use of Ion-Exchange Resin in Determination of Traces of

Copper . . . H . A . Cranston and John B. Thompson 323 Measuring Distribution of Particle Size in Dispersed Systems

W alter M . Dotts 326 N O T E S O N A N A L Y T I C A L P R O C E D U R E S

High-Speed Filter A id for Chromatographic A nalysis . . John B. W ilkes 329 Determination of Hydrogen in Highly Fluorinated Carbon

C o m p o u n d s ...J ' ' ____________

W . H . Pearlson, T. J . Brice, and J . H . Simons 330 Electronic M ake and Break for Relay Operation . . . .

R. B. Harvey 331 Automatic Cutoff for Electrically Heated Water Still . .

Lawrence M . White and Geraldine E. Secor 332 Reaction of Lead Soaps with Sodium I o d i d e ...

Robert S. Barnett 333 New Standard for Use in Ultimate A nalysis of Organic

Compounds . . . C . L. Ogg and C . O . W illits 334 Determination of Sulfur in Sulfur Compounds with Benzi­

dine fdydrochloride...W esley S. Plainer 334 Separation of 2,4-Dinitrophenylhydrazones by Chromato­

graphic Adsorption . J . D. Roberts and Charlotte Green 335 Arrangement for M ultiple p H Determ inations...

M ax D. Reeves 336 Modified Gas-Absorption A p p a r a t u s ... .

A rchie N . Bolstad and Ralph E. Dunbar 337 Electromagnetic Stirring Device . . William N . McIntosh 338 B O O K R E V I E W... 338 C O R R E S P O N D E N C E

Determination of p,p' Content of Technical DDT . . . . 339 Determination of E t h y le n e ...339 Suggestions to A u t h o r s ...340 Instrumentation in A n alysis . . R. H . M u ller (A d vt. Sect.) 23

The Am erican Chem ical S o cie ty assumes no respo nsib ility for the statements and opinions advanced by contributors to its publications. V ie w s expressed in the editOq^flEksre those o f the editors and do not necessarily represent the official position

° f th /jX j*e ric a n Chem ical S o cie ty.

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I N G C H E M I S T R Y Vol. 18, No. 5

S K I L L I S N O T E N O U G H . . . c a re fu l c h e m is ts ' S u p p le m e n t sk ill w ith th e b e s t in c b e m ic a ls. B y

s p e c ify in g M a llin c k ro d t A n a ly tic a l R e a g e n ts h ig h ­ e st q u a lity a n d u n ifo rm , d e p e n d a b le p u r ity a re a lw a y s a s s u re d .

S e n d for t h e M a llin c k r o d t A n a l y t i c a l R e a g e n t c a t ­ a lo g to g e th e r w i t h a n y specific in f o r m a tio n d e s ire d o n M a llin c k r o d t c h e m ic a ls to fit y o u r s p e c ia liz e d o p e ra tio n s .

A lw a y s S p e c ify M a llin c k r o d t R e a g e n ts In O r ig in a l P a c k a g e s

T a r ta r ic A c id

( Mallinckrodt)

M a g n if ie d to 10 D ia m e te r s

MALLINCKRODT

J 9 W e a ' i à o f7 ¿ ¡ jP & lw c e

M allin ck ro d t St., St. Louis 7 , Mo.

CHICAGO . PH ILA D ELPH IA

WORKS

72 G old St., N ew Y o r k 8, N. Y . LOS A N G ELES • MONTREAL

U N I F O R M • D E P E N D A B L E • P U R I T Y

May, 1946 A N A L Y T I C A L E D I T I O N

C

e n t r a l

S

c i e n t i f i c

C

o m p a n y S c ie n tific C tN (D f y p a ta tu i

N ew York BOSTON San Francisco C H IC A G O Los A ngeles TORONTO M ontreal M a in o ffic e a n d F a c to ry

1 7 0 0 Ir v in g P a rk R o a d , C h ic a g o 1 3 , I llin o is , U .S .A . C a b le a d d re s s : C e n co

SERVING SCIENCE

T h e C e n tr a l S cien tific C o m p a n y , e s ta b lis h e d in 1 8 8 9 , is k n o w n in t e r n a t i o n a l l y f o r th e m a n u f a c tu r in g a n d m e r c h a n d is in g o f s c ie n ­ tific in s tr u m e n ts a n d a p p a r a t u s fo r e d u c a tio n a l, in d u s tr i a l a n d c lin ic a l la b o r a t o r i e s . C e n c o ’s c o m p le te s to c k s f a c ilita te te s ti n g o f a ll ty p e s :

C o a l a n d C o ke D a ir y P ro d u cts F e rm e n ta tio n In d u s trie s Fo od a n d D ru g s H ig h w a y T e stin g Le a th e r a n d G lu e M e ta llu rg y

M illin g , B a k in g , G ra in s

P a in ts , V a r n is h e s , etc.

P a p e r

P e tro le u m P ro d u cts R u b b e r

S o ils a n d F e r tiliz e rs T e x tile s

V e g e ta b le O ils , S o a p W a ter a n d S e w a g e

A p p a r a tu s m a n u f a c tu r e d b y a n d b e a r i n g th e fa m o u s C e n c o tr a d e m a r k in c lu d e : D e K h o t in s k y d r y i n g o v e n s , in c u b a to r s , t h e r m o r e g u ­ la to r s , " P h o t e l o m e t e r s ” a n d " S p e c t r o p h o t e lo m e t e r s ,” H y v a c , P re s - so v a c , M e g a v a c , H y p e rv a c a n d S u p e rv a c p u m p s , T e n s io m e te r s , H y d r o p h il b a la n c e s , etc. C e n c o a l s o d is tr i b u te s i n t e r n a t i o n a l b r a n d s :

B a k e r’ s A n a ly z e d C h e m ic a ls • C o o rs P o r c e la in w a r e

" P y r e x ” a n d " V y c o r ” B ra n d G la s s w a r e • N o r m a * , E x a x a n d R e s is ta n c e G la s s w a r e • Leco C a rb o n a n d

S u lp h u r D e te rm in a to rs • W a rin g B le n d o rs

F o r a s s u r a n c e o f p r o d u c t, p ric e a n d s e r v ic e —-sp ecify C e n c o .

6 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 18, No. 5

Hydrogen Ion Concentrations c a n n o w

BE M EA SU R ED W ITH IN 0.1 pH W ITH ACCUTINT TEST

S im ple

^—

N o I n s t r u m e n t R e q u i r e d Can B e E m p l o y e d A n y w h e r e C o l o r S c a l e o n E a c h V i a l

M a s t e r C o l o r Chart G r a p h ic Correlatio n

ACCUTINT Test P ap ers a re sim ple, ra p id a n d a c c u ra te m eans of m aking h y d ro g e n ion determ inations. M erely p la c e a d ro p of th e solution b eing exam ined on a strip of th e test p ap e r, observ e th e color c h a n g e w hich occurs, th en m ake a com parison w ith th e p rin te d color sta n d a rd on the vial.

Each strip re acts to p ro d u c e a distinctive color re a c tio n at stated pH values w ithin its ra n g e or in d icates th a t an a d ja c e n t ra n g e m ust b e u sed for furth er determ ination.

ACCUTINT W ide R ange Test P ap ers perm it qu ick determ in atio n to establish the pH v alue w ithin 0.5 unit in th e ra n g e 0 to 14 pH w hile F ractional R ange ACCUTINT Test P ap ers e n a b le closer approxim ations to w ithin 0.1 an d 0.3 of 1 pH unit. W h e re a pH value ca n n o t b e closely estim ated, the use of w ide ra n g e p a p e rs is re co m m en d ed to localize th e pH v alu e suffi­

ciently for quick, effective use of fraction al ra n g e p ap ers.

ACCUTINT P apers a re as sim ple to use as Litmus P a p e r b u t a re m any tim es m ore inform ative: th e 23 different ra n g e s pro v id e 144 se p a ra te color reactions. ACCUTINT P apers a re fu rn ish ed in p a d s of 20 strips ea ch , five p ad s to a vial.

DISTRIBUTORS

E. H . S A R G E N T & C O . — 1 5 5 -1 6 5 E. Superior Street, Chicago 11, III.

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A c o v e r s r a n g e 0 t h r o u g h 5 p H B c o v e r s r a n g e 1 t h r o u g h 12 p H C c o v e r s r a n g e 9 t h r o u g h 14 p H P a c k e d i n v ia l, 5 p a d s , 100 s t r i p s

(P le a s e s p e c if y r a n g e s d e s ir e d ) F r a c t i o n a l R a n g e A C C U T IN T T e s t

P a p e r s (65c p e r V ial)

N o . F r a c t i o n a l R a n g *

1 0 ... 0 . 0 t h r o u g h 1 .2 2 0 ... 0 .8 t h r o u g h 2 .4 3 0 ... 1 .3 t h r o u g h 3 .3 4 0 ... 1 .4 t h r o u g h 3 .0 5 0 ... 1 .7 t h r o u g h 3 .3 6 0 ... 2 .7 t h r o u g h 4 .7 7 0 ... 3 .9 t h r o u g h 5 .4 8 0 ... 5 .0 t h r o u g h 6 .6 9 0 ... 5 .2 t h r o u g h 6 .9 1 0 0 ... 5 .3 t h r o u g h 7 .0 1 1 0 . . ... 6 .1 t h r o u g h 7 .4 1 2 0 ... 6 .9 t h r o u g h 8 .4 1 3 0 ... 7 .2 t h r o u g h 8 .8 1 4 0 ... 7 . 3 t h r o u g h 8 .8 1 5 0 ... 8 .4 t h r o u g h 9 .4 160 ... 8 . 9 t h r o u g h 1 0 .0 1 7 0 ... 9 .1 t h r o u g h 1 0 .4 1 8 0 ...10 .1 t h r o u g h 1 2 .0 1 9 0 ... 1 0 .7 t h r o u g h 1 4 .0 , 2 0 0 ... 1 2 .4 t h r o u g h 1 4 .0

P a c k e d i n v i a l , 5 p a d s , 1 00 s t r j ^ s ( P l e a s e o r d e r b y R a n g e N u m b e r s ) M a s t e r A C C U T I N T C o l o r C h a r t , 21 x 1 0 l i " , c o r r e l a t e s b y v a l u e a n d g r a p h i c a l l y a l l 144 p H v a l u e s , p e r c h a r t $ 3 .2 5 .

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May, 1946 A N A L Y T I C A L E D I T I O N

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I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 18, No. 5

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STURDY, COMPACTLY SHORT, SIMPLE CONSTRUCTION

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Extra h eavy w all m ercury reservoir.

3-w ay stopcock with tail outlet tilted, preventing over­

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WIDE RANGE

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I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 18, No. 5

TH E “ L U M E T R O N ” M ODEL 402-E

PHOTOELECTRIC COLORIMETER

A h ig hly p re c is e research instrument o f unusual versa tility

Designed to cover th e w idest possible field of application in chemical analysis by photoelectric m eas­

urem ents, the M odel 402-E L um etron Photoelectric C olorim eter is p articu larly suited for research purposes where v ersatility and reproducibility are of v ital im portance. W hile intend ed prim arily for th e m easurem ent of transm ission of liquids, accessories are available to extend the application of th e in stru m en t to the m easurem ent of fluorescence, ultrav iolet absorption, an d sca tte rin g effect of suspended particles. I t can also be used for th e m easurem ent of reflection of solid surfaces, pastes, powders, and opaque liquids.

Sam ple H o ld ers: A ccom m odates a g reat v ariety of sam ple holders from microcells to absorption cells of 150 m m . light p ath . B y m eans of an ad a p te r, test tu b es can also be used.

M onochrom atic F ilters: T he powerful light source and high galvanom eter sen sitiv ity perm it use of filters isolating narrow spectral bands. A set of 16 m onochrom atic filters is available to cover th e spectrum from 350 to 730 millimicrons.

B alanced Photocell C ircuit: T he Brice Circuit em ployed in this in stru m en t furnishes a strictly linear response and gives a high degree of s ta ­ bility. Line voltage variatio n s have no effect upon th e readings.

Tristim ulus F ilters: A set of 3 filters is available for readings in term s of th e “ IC I 1931 S tan d ard O bserver for C olorim etry.” M easurem ents can be carried out in transm ission as well as in re­

flection tests.

T urbidity M ea su rem en ts: M easurem ent of low degrees of tu rb id ity down to 1 ppm . an d less can be m ade with th e aid of 150 m m . sam ple holders.

.A special pick-up u n it m akes it possible to extend the range of th e m easurem ents down to 0.01 ppm .

M ercury Vapor Lam p: F o r fluorescence and ultraviolet absorption tests, a m ercury v apo r lam p can be su b stitu ted for the incandescent lam p an d th e colorim eter can be equipped with a q u a rtz optical system and m ultiple-reflection galvanom eter.

R eflection A dapter: An a d a p te r can be installed for m easurem ent of reflection of pastes and powders. T he M odel 402-E L um etron P h o to ­ electric C olorim eter has found extensive appli­

cation for stan dard izing color of food m aterials,' face powders, cem ent, etc.

A detailed 14-page descriptive folder on th e LU M ETR O N M odel 402-E is available upon request. T his bulletin contains detailed d ata on absorption cells, filters, accessories, optical and photoelectric system . Inqu iries are solicited regarding th e selection of su itab le equip­

m ent to particular applications.

W I L L C O R P O R A T I O N

ROCHESTER

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B U FFA L O A P P A R A T U S C O R P ., B U FFA L O S, N . Y.

L A B O R A T O R Y A P P A R A T U S A N D C H E M I C A L S

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LOW ACTINIC GLASSWARE

P y R t ñ

F O R A L L A R O U N D U S E . Y E A R ’ R O U N D E C O N O M Y

b r a n d L A B O R A T O R Y G L A S S W A R B

“P Y R E X " is a registered trade-m ark a n d indicates m anufacture by

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.

H E R E is a c o lo r e d g la s s w a r e w h ic h c a n b e o f u tm o s t v a lu e in y o u r f o o d r e s e a r c h a n d c o n t r o l w o r k .

I t c o m b in e s th e a b ility to r e ta r d d e t e r i o r a t i o n d u e to l i g h t in flu e n c e * w ith a ll th e o t h e r p r o t e c ­ tiv e q u a litie s o f P y r e x C h e m ic a l G la s s , N o . 774

— m e c h a n ic a l s t r e n g th , c h e m ic a l s ta b ility a n d th e r m a l r e s is ta n c e . T h e L IF E T IM E R E D c o l o r is p e r m a n e n t — a n i n t e g r a l p a r t o f th e g la s s its e lf.

N o w a v a ila b le in a v a rie ty o f u s e fu l l a b o r a t o r y f o r m s — b e a k e rs , flask s, tu b e s , p ip e tte s , e t c . —

“ P y r e x ” L o w A c tin ic W a r e is fu lly d e s c r i b e d in C a ta lo g L P 24 .

*A pproxim ate percent wave-length transm is- f 3000 A ngstrom s. .0%

sion in A ngstrom units of “ Pyrex" Brand J 4000 A n g stro m s.. 1%

L IF E T IM E R E D Low A ctinic G la ssw a re .. . 15000 A ngstrom s. .4%

C orning

m eans ---

Research in Glass

12 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 18, No. 5

C O N T R O L E Q U I P M E N T P A Y S

D E T R O I T 4 , M I C H 9 3 3 0 R O S E L A W N

MOISTURE T ELLER W ill dry a fifty gram s a m p l e of« h i g h perm eability in o n e m in u te b y fo rc in g e le c tric a lly h e a te d air th ro u g h th e test sam ple. T e s t is in exact m o istu re p er­

c e n ta g e b y g r a v i­

m etric m e th o d . N o c o rre c tio n s o r c a li­

b r a t i o n s a r e r e ­ q u i r e d . O p e r a ti n g co st is very low .

DETERMINATOR

T h e im proved 2 M in u te C arb o n D e te rm in a to r enables o p erato r to d eterm in e eith er p relim inary o r final carb o n c o n te n t o f all m etals w ith speed an d accuracy.

N e w features elim in ate m u ch o f th e h u m a n e q u atio n a n d sim plify p ro ced u res. C o m p lete d e te rm in a tio n can b e m ad e w ith in 2 m in u tes after sam p le is w eig h ed . A 2 m in u te s S u lp h u r D e te rm in a to r is also available.

V A R I T E M P COMBUSTION

The unique construction o f the Varitemp Combustion Furnace combines transformer, pyrometer, oxygen valve, voltage control switches, power switch and furnace in a single unit. Constant Temperature assured. All parts well protected for maximum efficiency. Temperature range up to 2750 dee. Fahr. Single Tube Furnace. $177.00 . . . D ouble Tube Furnace, $230 F.O.B. D etroit.

B. F. Goodrich Chemical Company

h a s a v a i l a b l e f o r s a l e t h e s e o r g a n i c c h e m i c a l s

•• ... - - u

H )

r f i ^ ' C O a H - 0 3 i - Di B Naphthyl P Phenylene U J

Phenyl B Naphthyl Rmine ^ . Diamine

M V 107 V

pûrUy 9B.0%

Diamine merc¡ai quantities

‘■ H T S ” ”r puiliy

98.0/0 % • • • •

..

M P. 23 L,

Purity 98% ! .

!

>... H O O ^ O I

Q “ « 0 - C' v" : M onoberal " 'J 1**'2 ? Diphenyl Amines liphenyl flmi , , auanUtla, ,o, „„„„««** • Puritv

9 0

%

Available In com 145_245

D is tilla tio n r a n g e - '“

(3.° mm)

Purity 98/0 • • • • • • ----

b Q C H

p O ° CH^ i f f

O S O « ' " ' : Dibenzyl Ether of Hydronui* |

,sopr.pory '•

A v a ila b le In com m ercial

q

^{. M . P . *19}

(A

P .

7Zt , • Purity 8570

Purity 92% mln- . ... ...

... ... fc»I>CTO ù

* • • • • • • • • • • • • • • r ^ S n o H • i nwanthogen V CH;5

p Hydrox, Dipheay'

A v a i l a b l e In c o m m e r c t a q

f t t ’ *%

0 * 0 ° * •: DilsopropylDixanthofen V C H *

I Available i n com m ercial q«

• i* p 52°

I Purliy 98 %

: ...

. * * * |flíxeV K hyl*añd Dimethyl c » , - y " + c 6 » j

► • • • • • • • • • • • • ,_,

n

O;—, • Mamantothiazoles C H ^ _ c - S

H-Hitroso O iphaiï' »™“ —

A v a i l a b l e

in

c o m m e r c i a

q

M . P- 6 * °

Purity 97%

Klixea tinji,«*«“ "■

r-^P r\ I Mercaptothiazoles

O * ' - ' S Available in com m ercial

‘’'’M T * 136-1530 C ¿ H s_ < Ü f C 5 H

Approximately «. /

Pur,,Y 85% dimethyl H - C - 5 and 15% eth yl

m ercap to lh iaio les

: .

... : ... r , u . - c - N » ]

..

Diphenyl p

P h e n y te n e

Drenàne

A v a i l a b l e

In

c o m m e r c i a l q « a M . P- 14 4 IL

Purity 92%

w

q

I Q ^ O : Mixed AliphaticThiazyl

I Disulfides .

•

A . . „ ï i « b l e

in

c o m m e r c i a l

¡sulfides —

A v a i l a b l e

in

c o m m e r c i a l

U H?- C

r t.m n titie s

q u a n t i t i e s

liquid

For ad d itio n al info rm atio n p le a s e w rite B. F. G oodrich Chemical C om pany, D e p a rtm e n t CA-5, Rose Building, C leveland I S , O hio.

B. F. Goodrich Chemical Company

THE B F. GOODRICH COMf AMY

14 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 18, No. 5

DU PONT

A n o th e r F o rw ard D ev elo p m en t in In secticid es

HEXA CH LOROCYCLOHEXAN E is a new and o u tstan d in g insecticide. In th e a n n u a l H u rte r M em orial L ectu re, delivered on M arch 8 , 1945, by D r.

R. E. Slade, R esearch C o n tro lle r of Im perial C hem ical In d u strie s, he stated , " T h e re has now com e to lig ht w h a t prom ises to be o ne o f scien ce’s im p o rtan t c o n trib u tio n s to th e w elfare o f m a n .” D r. Slade re ferred to H exachloroeyclohexane w hich was developed as an insecticide by Im perial C hem ical In d u strie s u n d e r th e follow ing add itio nal nam es: benzene hexa- cldoride, 666 , and G am m exane.

\

D u P o n t has confirm ed th e B ritish reco rds of efficiency o f th is re m a rk ­ able insecticide in its own lab o rato ries, an d is privileged to a n n o u n c e it will h av e H e x achloroeycloh exane available th is season in m o d era te q u a n ­ tities fo r ex p e rim en tal use. In q u irie s from researc h in stitu tio n s an d qu ali­

fied in v estig ato rs are invited, an d on re q u e st a copy o f D r. S lade’s le c tu re will be m ailed as soo n as it is available for d istrib u tio n . G rasselli Chem icals D ep artm en t, E. I. du P o n t de N em ou rs & C om pany, (In c.), W ilm ington 98, D elaw are.

c ^ P O H î

U .S . PAT.Off-

5

B E T T E R T H I N G S F O R B E T T E R L I V I N G . . . T H R O U G H C H E M I S T R Y

May, 1946

QUICKER ANSW ERS

Com putation time 1 / 5 to 1 / 1 0 that required by m ech an ical ca lc u la to rs.

E A SY TO OPERATE

Short o p eratio n train in g p eriod.

E A S Y TO IN STA LL AND MAINTAIN O p e rate s from lighting circuit.

W rite fo r new descriptive bulletin.

L I D A T 1 D E N G I N E E R I N G C O R P O R A T I O N

620 NORTH LAKE AVENUE • PASADENA 4, CALIFORNIA

H-5330

T T

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“*■ °r hundreds of laboratory applications, Stainless Steel Beakers, available in six sizes from 1200 ml. to 8000 ml., offer a full measure of convenience and a high level of performance, notwithstanding their comparatively low cost.

Built especially for those requirements demanding long use under severe service conditions, Harshaw Stainless Steel Beakers are made of 18-8 solid metal, rust-proof, and cannot chip, scale or peel. They are tough, strong and highly resistant to denting, scratching, abrasions and binding.

Size A B C D E F

Capacity, m l.. .

_{2 0 0 0}

3300 4000 5800 8000

Diameter, mm, . ... 125 140 175 180 200 225

Height, mm... ... 145 175 180 190 ■ 225 250

Each... $3.25 $4.00 $4.75 $6.25 $7.25

10% Discount allowed when purchased in lots o f 12— one size or assorted.

HARSHAW SCIENTIFIC

DIVISION O F THE HARSHAW CHEMICAL CO.

C LE V E LA N D 6, OHIO

H A R S Ï^ r ï

S T O C K S A L S O C A R R I E D I N C I N C I N N A T I • D E T R O I T • P H I L A D E L P H I A I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 18, No. 5

S T A IN LES S STEEL

B E A K E R S

May, 1946

I N P U T C O N T R O L !

In addition to providing your lab o rato ry and shop with re liab le facilities fo r fa s t, accurate m etallurgical tests, chemical analyses qnd many other jobs requiring tem­

peratures up to 2 0 0 0 ° F., the famous Lindberg Box Furnace with "S te p le ss” Input Control soon p ays for itself in current save d .

During a recent test this furnace consumed only 6 0 .3 kilowatts o f current, maintaining a tem perature of 1 6 5 0 ° F. fo r seven d a ys. O peratin g under the same conditions fo r a like period with the conventional rheostat required 1 10 K W o f current. A t C hicago rates this saving o f 5 0 K W H p e r w eek would amount to

$ 7 2 .8 0 in one y e a r.

The “ Stepless” Input Control, enclosed in a se p arate metal case with an Indicating Pyrom eter, em ploys a synchronous motor to autom atically m ake and b rea k the current. This supplies just the right amount needed to maintain an EXA CT tem perature level. The need fo r a w asteful rheostat is entirely elim inated. The control can be mounted conveniently n ea r furnace and p o w er lines.

The h ea vy one-piece, rod-type nickel chromium

elements a re simple and e a sy to rep lace as the use of nuts and bolts is elim inated. A built-in transform er fo r low vo ltag e current m aterially prolongs element life.

The door is o f a modern counterbalanced, vertical-lift design that keeps the hot side a w a y from the o p era to r.

Along with rem arkable savings in current consump­

tion, installation and m aintenance costs a re also un­

usually low.

Your lab o rato ry equipment d e a le r will be glad to supply you with complete information on this reliab le Lindberg Box Furnace to d ay. Also ask him about Lindberg Combustion T yp e and Pot Crucible Furnaces as w ell as Lindberg Lab o ra to ry Hot Plates.

LIN D B E R G E N G IN E E R IN G C O M P A N Y

2450 W. H U BBARD STREET • C H IC A G O 12, ILLINOIS

W E L L K N O W N T H R O U G H O U T T H E W O R L D A S L E A D E R S I N D E V E L O P I N G A N D M A N U F A C T U R I N G

I N D U S T R I A L H E A T T R E A T I N G E Q U I P M E N T

18 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 18, No. 5

INTERMEDIATE MODEL

W I L E Y L A B O R A T O R Y M I L L

For th e rapid m illin g of homogeneous sam ples of a great variety of com m ercial m aterials for laboratory an alysis

4 2 7 6 - M .

R e c o m m e n d e d f o r la b o r a to r y B a r le y I l u s k s .

B a r le y , M a l t i n g B lo o d , D r ie d C o c o a N ib s C o r n S t a l k s C o t t o n C l o t h

C o t t o n S e e d a n d C a k e D a t e S e e d s

D ig i ta l is E r g o t G r a s s , D rie d H a i r , R a b b i t M e t h y l M e t h a c r y l a t e

t h e p r e p a r a tio n o f s a m p le s o f:

O a t s P a p e r

R a y o n J e r s e y C lip p in g s S h r i m p S h e lls

S o y B e a n s a n d C a k e T a n k a g e H a i r T i n F o il T o b a c c o S t a l k s W h e a t

W o o d S t r i p s , ( l i g h t ) W o o l Y a r n ,

E t c ., E tc .

LABORATORY M ILL, W iley In te rm e d ia te M odel. A rugged, com pact, m o to r driven m odel as suggested by th e U. S. B ureau of P la n t In d u s try for th e rap id m illing of la b o ra to ry sam ples of m aterials tissue or sim ilar m aterials, b u t since found suitable for a great v a rie ty of com m ercial

W ith polished cham ber 40 m m d iam eter X 22 m m deep, two s ta tio n a ry blades, an d ro to r w ith four cu ttin g edges which revolves a t high speed to produce a shearing action which prev en ts loss of m ois­

tu re from heat. This M ill will prepare a 20 gram , 40 m esh sam ple of dried p la n t stem tissue in 15 to , rainu tes; a sim ilar sam ple of ex tracted leaf tissue in 7 to 10 m inutes, or of JX-inch nieces of soy­

bean stem s in o to 7 m inutes, which figures ind icate th e o peratin g speed. T h e M ill has m an y o th er

« 4 ^?h 'f prCparmg f;om °gene°us sam ples. D ried sam ples are generally essential,- b u t tobacco w ith 12 % m oisture vras m illed satisfactorily.

In use, sam ples are introduced through nickel plated hopper 2 % inches diam eter a t top X 2 jX inches deep, and agitated by the high speed of th e rotor until cut to sufficient fineness to fall through the sieve top of the rem ovable delivery tu b e which forms the bottom of th e M ill chamber. Six interchange­

able, sieve top, nickel plated brass delivery tubes of 10, 20, 30, 40, 60 and 80 mesh, re­

spectively, are regularly available. T he 80 mesh size lacks ruggedness for general use b u t has been found convenient for p lan t tissue which has first passed the coarser screens.

A removable, polished p la te of glass forms the face of the chamber, an d perm its observa­

tion of the sample during operation, and makes possible easy access to the entire interior for cleaning. Five speeds from 897 to 3800 r.p.m .

are available b y changing th e position of an endless V-shaped belt. A new' feature is th e arrangem ent for collecting samples. A screw- top jar, 4 oz. capacity, can be attac h ed directly to th e delivery tu be by m eans of a special m etal threaded ad ap ter which fits th e lo v er end of the delivery tube, so th a t sam ples need n o t be transferred after milling as th e threaded ad a p te r top can be rem oved and replaced by th e plastic cap regularly supplied w ith the glass jar. Small sam ples are collected in a receiver 22 m m square X 19 mm deep, which fits directly over th e lower end of th e delivery tube.

M ounted with a 3 ^- 6 th h.p. continuous d u ty m oto r on sub stantial cast iron base w ith ru b ­ ber feet. Overall dimensions 13% inches long X 11 inches deep X 11% inches high. N et weight 45 lbs., shipping weight 67 lbs

4 2 7 6 -M . L aboratory M ill, W iley In te r m e d ia te M o d e l, as a b o v e d escrib ed . C o m p le te w ith h o p p er 2 in ch es d ia m ete r „•¡ti, j p lu n g e r ; th r e e d e liv e r y t u b e s w ith s ie v e to p s of 2 0 . 4 0 a n d 60 m e sh , r e s p e c tiv e ly e a c h w ith r e r e f t e r „ S ’ V- c o v e !V w o o <ien tw o e x t r a s t a t i o n a r y blades and wreneW fnr ® A v !a c P y 11« r e c e iv e r f o r c o lle c tin g s m a ll s a m p le s ;

e: I.hrPiWleH f 4 „ - : . r- .

. E lobx

A R T H U R H. T H O M A S C O M P A N Y

RETAIL—WHOLESALE—EXPORT

LABORATORY APPARATUS AND REAGENTS

W ES T W A S H IN G TO N SQ UARE, P H IL A D E L P H I A 5, U. S. A.

C able Address “ B alance,” P hiladelphia

INDUSTRIAL ^{a n d} E N G IN E E R IN G CHEMISTRY

P U B L I S H E D BY

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 W A L T E R J. M U R P H Y ,

E D I T O R

Style Requirements

I n Ap r i l

we discussed editorially the field which the

* An a l y t i c a l Ed i t i o n

should endeavor to include in its coverage, emphasizing its desire to p rin t more papers on evaluation of analytical results, statistical tre a tm e n t of analytical d ata, principles and theory of analytical chem istry, and college training of personnel.

T he

An a l y t i c a l Ed i t i o n

is in position to p rin t all such m aterial prom ptly.

M anuscripts offered for publication differ widely, not only in scientific value b u t in their presentation. Some are well w ritten, logically developed, concisely w ritten, yet giving all necessary details. W hen these m anu­

scripts are typed double space, w ith wide m argins to allow room for directions to the printer, and arc ac­

companied by drawings and photographs from which engravings can be m ade w ithout retouching or reletter­

ing, they gladden the editor’s heart.

Others, however, fail to m eet these specifications, and it is to authors of such papers, as well as to those who have no t previously contributed to our pages, th a t this editorial is directed.

T o be of the g reatest service the scientific- facts m ust be presented in a clear, logical readable m anner.

An im p o rtan t p oint to be kep t in m ind in writing any article is the type of reader to be reached. Readers of the

An a l y t i c a l Ed i t i o n

are. intelligent scientists, who do n o t need schoolbook directions for laboratory pro­

cedure; th ey do need to be given sufficiently explicit directions so th a t they can rep eat the work reported, if need be.

W hen a scientist has work to report in a certain journal—the

An a l y t i c a l Ed i t i o n

or any other—he should familiarize himself w ith th a t jou rn al and model his report on particularly good papers published there.

AMittle tim e devoted to thinking the article through before p u ttin g pen to paper will pay dividends in pro­

ducing a logical, concise, and readable presentation th a t avoids repetition y e t gives all the facts. An outline m ight be set up, for instance, as ( 1 ) why the work was done, w ith a brief reference to previous work, properly docum ented, ( 2 ) a concise account of w hat was done, with all necessary details as to apparatus, reagents, and procedure followed, and (3) the result of the investiga­

tion and conclusions drawn.

A short ab stra ct th a t can be prin ted a t the beginning of the article is a great help to the busy reader, as it enables him to decide a t once w hether to read the article in full then and there, to lay it aside for later atten tio n, or to skip it. as outside his field of interest.

Too m any m anuscripts give th e impression th a t the au tho r has dictated a chronological account of w hat he has done in the laboratory or—worse—has asked bis secretary to copy hand-w ritten notes and then has failed to read the m anuscript over and check it for ac­

curacy. A good secretary will take care of misspelled words and punctuation, b u t cannot always in terp ret carelessly w ritten figures or chemical terms. F ootnotes are too often an indication of sloppy thinking. T he m aterial there given m ight b e tte r be incorporated in the tex t or p erh ap s presented in a separate note.

L iteratu re citations should be carefully checked for accuracy and completeness.

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

p rin ts them a t the end of each article, arranged alphabetically by authors, and w ith corresponding num bers inserted in the te x t a t appropri­

ate places. T he abbreviations used are given in the

“ L ist of Periodicals A bstracted by Chemical Abstracts”.

T he spelling and nom enclature approved by th e

S o ­

c i e t y’s

C om m ittee on N om enclature, Spelling, and P ronunciation are followed. T his subject has been re­

cently discussed in the introduction to the 1945 subject index to Chemical Abstracts. T he M erriam W ebster dictionary is followed as th e au th ority for deciding on the spelling of nontechnical words.

Specifications and directions for preparing copy, in­

cluding illustrations, are given in “Suggestions to A uthors” , copies of which will be sent on request to any who are interested. A sum m ary is printed on page 340 of this issue.

H aving a definite bearing on the question of the preparation of chemical papers is w hat seems to be a re­

grettable lack of cooperation between th e departm ents of chem istry and o f English in m ost of our colleges and universities. I f the ability to w rite a clear, concise rep o rt is n o t developed during the college course, i t is acquired only w ith difficulty after graduation. Is no t this a subject th a t should be given greater considera­

tion by our chemical educators?

279

Improvement of Precision by Repeated M easurem ents

A p p l i c a t i o n to A n a l y t i c a l C ontrol M e t h o d s

J O H N M A N D E L 1 Columbia University, N ew York, N . Y .

This article critically examines replication of measurements as a means of increasing precision. Formulas are provided for evaluating such improvement of precision in any given case and for computing con­

fidence limits in routine analysis.

I

N A previous p aper (2) i t was shown how th e estim ation of th e precision of analytical m ethods can be accom plished by m eans of m odern sta tistic a l theory. T h is article considers in d etail some questions arising in th e stu d y of precision.

W hile th e practice of a t le a s t duplicating every analysis is well established am ong analysts, th e increase in precision th u s brought a b o u t has seldom been considered. H ow ever, th is question appears to be of considerable im portance, as can be inferred from th e following considerations.

In th e practice of routine analysis, i t is custom ary to obtain som e indication a b o u t th e precision of analytical results from the

“ closeness” of th e replicate d eterm inations (generally duplicates) m ade b y th e analyst. In som e cases th e optim istic picture thus obtained is tem pered by th e knowledge, gained through experi­

ence, th a t th is closeness is very often grossly m isleading. M oran (8) has given som e a tte n tio n to th is m a tte r, and has stu d ied it ex­

perim entally on th e basis of d a ta o b tain ed in his laboratories.

H aving found t h a t th e ra tio of th e sta n d a rd deviation of single determ inations to t h a t of averages of duplicates was 1.05—a p ­ preciably less th a n th e th eo retical value \ / 2 for th e case of tru e random determ inations— M oran (8) ascribes th is result to th e fact t h a t “ d u p licate analyses m ade a t th e sam e tim e are n o t truly' random b u t are r a th e r influenced by slig h t v ariations in technique o r surrounding conditions” .

F In a population of variance a 2, th e variance of th e m ean of a random sam ple of n is a-2/ n ; th e corresponding sta n d a rd deviation is th u s c r/V n . T h e ratio m entioned above is, therefore, in the case n = 2, — a— = = V 2 = 1.41 . . .

< r/V 2

M oran calls th is ra tio th e “ ra tio of im provem ent by duplica­

tio n ” . I t seem s preferable to consider th e ra tio of th e variances, th e squares of th e sta n d a rd deviations; th e n th e theoretical value for duplication is sim ply 2; for n-fold replication i t will be n. T h e ad v an tag e lies in th e intuitiveness of th e in terp re­

ta tio n . On th e o th er hand, th e sta n d a rd deviations referred to in M oran’s “ ra tio of im provem ent” a re “ p opulation param ­ ete rs” —i.e., fixed th ough unknow n co n stan ts characterizing th e d istrib u tio n of errors in th e case considered. N ow these q u an ti­

ties being unknown, we s u b s titu te for th em estim ates derived from th e d a ta available; b u t such estim ates are obviously sub­

ject to fluctuations or, in sta tistic a l term inology, to “ sam pling errors” . T hus in considering th e ra tio 1.05 o btained by M oran, it is well to keep in m ind th a t a rep etitio n of th e whole experim ent m ight have given a q u ite different value, perhaps 1.23, w hich is alread y m uch closer to th e num ber 1.41 based on th e hypothesis of random ness. F o r th is reason i t becomes desirable to infer from th e d a ta available n o t only th e estim a te d ratio , b u t also a n evalu­

ation' of th e precision w ith w hich i t is obtained.

T his m a tte r, am ong o th e r things, is discussed in th e following pages; form ulas are given, based on th e th eo ry of statistics, for determ ining various q u an tities w hich are of in te re st in th is con­

n e c tio n . T h e calculations involved in th is ty p e of analysis of

1 P r e s e n t a d d r e ss. T h e B G C o rp o ra tio n , 136 W e s t 5 2 n d S t ., N e w Y o rk , N , Y .

d a ta , w hich will be seen to be simple an d on a n elem entary level, are'described in Section I I I and illu stra te d in Section V I b y m eans of th e d a ta given in M oran’s paper (S). T he read er is, however, strongly urged to give careful consideration to Section I, where th e chemical situ a tio n is described to which th e proposed m ethod is applicable. I t cannot be expected— as i t never can be in th e practical application of theoretical considerations— th a t th e con­

ditions of Section I will be exactly fulfilled. I t is ra th e r a m a tte r of personal ju d g m en t on th e p a r t of th e chem ist to decide w hether th e conditions in his case correspond sufficiently to th e theoretical m odel described to p erm it application of th e p resen t m ethod.

Such subjective ju d g m en t can efficiently be supplem ented by sta tistic a l te s ts of random ness, of equality of precisions, and th e like (cf. 10).. W hile th ese te s ts are valuable in t h a t th ey offer m eans of evaluating in a n objective a n d consistent w ay a v a rie ty of im p o rta n t aspects connected w ith th e precision of an a­

lytical m ethods, th e a u th o r feels t h a t th e y will in general n o t be necessary for th e application of th e m ethod proposed in th is paper, provided th e an aly tical procedure in question is well de­

fined in its various steps. T his po in t is b ro u g h t o u t m ore clearly in th e following discussion.

I. APPLICABILITY O F THE TEST

Suppose t h a t in order to gain q u a n tita tiv e inform ation ab o u t th e behavior of a n an aly tical procedure in routine work, th e re­

search an aly st devises one of the following experim ents:

1. A sam ple, containing v% of th e considered constituent, is stored and analyzed a t regular in terv als! say every m onth, for a period of M m onths, by th e sam e chemist, in Ar-fold replication each m onth. T h e N replicate determ inations are to be perform ed as closely to g eth er as th ey are expected to be m ade in ac tu a l rou­

tin e w'ork. T h u s M series, of N parallel determ inations each, are obtained.

2. A sim ilar experim ent is perform ed, involving several ana­

lysts, w ith th e understanding, however, th a t (a) every series of N replicates is perform ed by one an aly st only; and (6) a random experim ent is perform ed to select th e an aly st for every series.

T h u s if 4 analysts are available, 4 slips of paper, one of w hich is m arked, are thoroughly mixed, a fte r w hich every chem ist draw's one slip; whoever draw s th e m arked slip perform s th e series of analyses for th is m onth, regardless of possible repetitions due to chance.

3. T h e ty p e of experim ent is modified, in t h a t M laboratories are selected a t random (in so far as th is is feasible, considering th eir su itab ility for th e given ty p e of analysis, etc.). In this case it m ay be superfluous to space th e M series in tim e: M sam ples of th e sam e m aterial are se n t sim ultaneously to th e vari­

ous laboratories.

4. A ny sim ilar ty p e of experim ent can be considered, w ith th e tw ofold restriction, however, t h a t (a) only one an aly st m akes th e IV replicates in a given series; an d (6) th e series are m ore or less random w'ith respect to th e facto r w hich is considered to cause m arked discrepancies betw een series, such as laboratory, chem ist, w eath er conditions, etc.

U nder th ese conditions th e following assum ptions are m ade A. T o every series, say th e ith , corresponds a “ population m ean” (w'hich m ay be in terp re ted as th e m ean of all th e analyses, in infinite num ber, w'hich could be perform ed under th e sam e stab ility of conditions as prevailed for th e N analyses actually perform ed in th is series). As pointed o u t b y M oran, one should n o t in general expect th is m to be equal to v, even in th e case of a very accurate m ethod of analysis, since slight vari­

ations in th e surrounding conditions will influence sim ilarly all th e results of th e series.

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