Industrial and Engineering Chemistry : analytical edition, Vol. 14, No. 7

INDUSTRIAL ^AND ENGINEERING CHEM ISTRY

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

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H A R R ISO N E. H O W E, E D IT O R « ISSU ED JU L Y 16. 1942 » V O L. 14, N O . 7 « C O N S E C U T IV E N O . 14

F ie ld T e s ti n g o f M o l d - R e s is ta n t P r o p e r tie s of I n t e r i o r O il P a i n t s ...Alex M. Partansky 527 D e te r m in a tio n o f S m a l l A m o u n ts o f B e n z e n e in

P re s e n c e o f C y c lo h e x a n e a n d of T o lu e n e in P re s e n c e o f M e t h y l c y c l o h e x a n e ...

B. B. Corson and L. J. Brady 531 C le a n in g P o r c e la in C ru c ib le s . John E. D. Carwardine 533 S u lf a n ila m id e , S u lf a p y r id in e , S u lf a th ia z o le , S u lf a -

g u a n id in e , a n d S u l f a d i a z i n e ...

. J. A. Calamari, Robert Hubata, and P. B. Roth 534 R a p id D e te c tio n o f G o ld b y E le c tr o g r a p h ic M e th o d

J. A. Calamari, Robert Hubata, and P. B. Roth 535 E s ti m a t io n o f O r th o - , P y ro - , M e ta - , a n d P o ly p h o s ­

p h a te s i n P r e s e n c e o f O n e A n o t h e r ...

Loren T. Jones 536 P r e s s u r e - M e a s u r in g D evice fo r M o d e r a te V a c u a . .

Ernest R. Kline 542 O p tic a l A c tiv ity o f S o m e C in c h o n a A lk a lo id s a n d

S o m e o f T h e ir S a lt s i n M ix tu r e s o f W a te r a n d E th y l A l c o h o l ...James C. Andrews 543 Oil A b s o r p tio n o f P i g m e n t s ...M. A. Azam 545 D e te r m in a t io n o f T h io s u lf a t e i n U sed D o c to r S o lu ­

ti o n ...Karl Uhrig and Harry Levin 547 A p p a r a tu s f o r C o n ti n u o u s C o n c e n tr a tio n o f S o lu ­

t i o n u n d e r R e d u c e d P r e s s u r e . Benjamin L. Davis 548 D ro p p in g M e r c u r y E le c tro d e • . ■ G eorge J, Kahan 549 N o m o g ra p h f o r C o m p u t in g C o m p o u n d C o m p o s i­

tio n s o f P o r t l a n d C e m e n t s . . . . Benjamin Janer 550 I n je c tio n a n d S a m p lin g S to p c o c k . . Earl H. Brown 551 F r a c t io n a t io n o f C o llo id a l S y s t e m s ...

George Fancher, S, C. Oliphant, and C. R. Houssiere, Jr. 552 S ilico n , M a n g a n e s e , C h r o m i u m , I r o n , a n d C o p p e r

i n N ic k e l-B a se A l l o y ...Louis Silverman 554 G ra p h ic M e th o d o f S tu d y i n g S e p a r a t io n o f M ix tu re s

b y I m m is c ib le S o l v e n t s ...

Lila F. Knudsen and Donald C. Grove 556 S ta n d a r d M e th o d s f o r S a m p lin g a n d A n a ly sis of

C o m m e rc ia l S o a p s a n d S o a p P r o d u c ts , R ev ised . F. W. Smither and Committee 558

D ye E x tre m e ly S e n s itiv e to C o p p e r . . E. I. Stearns 568 E ffe c t o f C o n ta i n e r o n S o lu b le S ilic a C o n te n t of

W a te r S a m p le s . . . . C. A. Noll and J. J. Maguire 569 F lu o r e s c e in a s I n d i c a to r i n B r o m o m e tr ic T i t r a t i o n s

F. L. Hahn 571 P h o to e le c tr ic P h o t o m e t e r f o r R a p id G r a d in g of

N a v a l S to r e s P r o d u c t s ...Robert H. Osborn 572 S im p le H y d ro g e n S u lfid e G e n e r a t o r ...

Bryant W. Pocock, L. Scholten, and Paul J. Erickson 575 H ig h -S p e e d R o ta t io n a l V is c o m e te r o f W id e R a n g e .

Henry G reen 576 S im p lifie d A p p a r a tu s fo r C a ta la s e D e t e r m i n a t i o n .

Robert R. Thompson 585 S im p lifie d D ro p p in g M e r c u ry E le c tro d e fo r P o la r o -

g r a p h ic A n a l y s i s ...R. C. McReynolds 586 L a b o r a to r y T e m p e r a tu r e a n d H u m id i ty C a b in e t fo r

S tu d y in g H y g ro sc o p ic P r o p e r tie s o f T o b a c c o . . L. H. Davis, A. W. Petre, and C. F. Bailey 587 T e m p e r a tu r e - a n d H u m id i ty - C o n t r o l le d D ry e r fo r

C h e m ic a l E n g in e e r in g L a b o r a t o r y ...

Robert M. Schaffner and James Coull 590 S im p le V is c o m e te r fo r R e s e a rc h a n d C o n tr o l . . .

Frank C. Croxton 593 E le c tr o m a g n e tic D e n s it o m e te r . . . A. R. Richards 595 M IC R O C H E M IS T R Y :

D e te c tio n o f O r th o p h o s p h a te s b y M e a n s o f D ro p R e a c tio n s . Philip W. West and Thomas Houtman 597 M ic r o e s tim a tio n o f B ro m id e a s P e n ta b r o m o -

r o s a n i l i n e ...Wm. J. Turner 599 D e te c tio n a n d Q u a n tit a ti v e D e t e r m i n a t i o n o f

4 - A m i n o - 2 - m e th y l - l- n a p h th o l . Amel R. Menotti 601 M ic ro b io lo g ic A ssay o f N a t u r a l P a n t o t h e n i c A cid

i n Y e a s t a n d L i v e r ...

Eleanor Willerton and Hobart W. Cromwell 603 D ire c t D e te r m in a t io n o f S u lf u r . . . .

G. L. Mack and J. M. Hamilton 604 N ew M ic r o te s t fo r I o d i d e ...

David Hart and Robert Meyrowitz 606

T h i 8 . . . « . . . - , . « .« ■

25,900 copies of th is issue p rin te d .

Publication O f f i c e s E a s t o n , P e n n a .

E d i t o r i a l O f f i c e ! 1 1 5 5 1 6 t h S t r e e t , N . W . , W a s h i n g t o n , D . C . T e l e p h o n e ! R e p u b l i c 5 3 0 1 . C a b l e t J i e c h e m ( W a s h i n g t o n )

Pu b lish ed b y th e A m erican C hem ical Society, P u b lic a tio n Office, 2 0 th &

N o rth a m p to n S ts ., E a a to n , P e n n a . E n te re d as second-class m a tte r a t Uie P o st Office a t E a s to n , P e n n a ., u n d e r th e A ct of M arch 3. 1879, as 24 tim cs a year In d u s tria l E d itio n m o n th ly on th e 1st; A n aly tical E d itio n m o n th ly on th e lo th . A ccep tan ce fo r m ailing a t s p e c ia l.ra te of p o stag e p ro v id ed lo r m Section 1103, A ct of O c to b er 3, 1917, a u th o riz e d J u ly 13, 1918. .

A nnual su b sc rip tio n ra te , In d u s tria l E d itio n a n d A n a ly tic al E d itio

•old only as a u n it, m em b ers *3.00, o th e r $4.00. F o r e i g n p o stag e to co u n tries n o t in th e P a n A m e ric a n U n io n , $2.25; C a n a d ia n p o stag e , $0.75. sin g le

S p e c i a l L i c e n s e T E C - W - 3 2 4 A d v e r t i s i n g D e p a r t m e n t : 3 3 2 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 : B r y a n t 9 - 4 4 3 0

copies: In d u s tria l E d itio n , $0.75; A n a ly tic a l E d itio n , $0.50. S p ecial ra te s to m em bers.

N o claim s c an b e allow ed fo r copies of jo u rn a ls lo s t in th e m ails un less su ch claim s a re receiv ed w ith in 60 d a y s of th e d a te of issue, a n d no claim s w ill be allow ed for issues lo s t as a re s u lt of in su fficien t n o tice of ch an g e of a d d ress. (T en d a y s' a d v an c e n o tic e re q u ire d .) “ M issin g from files”

c a n n o t be acc e p te d as th e re a so n fo r h o n o rin g a c laim . A d d ress claim s to C h arles L . P arso n s, B usiness M an a g e r, 1155 16 th S tre e t, N . W ., W ash in g to n D . C ., U. S. A.

4 I N D U S T R I A L A N D J E N G I N E E R I N G C H E M I S T R Y

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

LABORATORY FURNACES MULTIPLE UNIT ELECTRIC EXCLUSIVELY

REG. U. S. PAT. OFF.

M I L W A U K E E , W I S C O N S I N

• Bow ne Hall of Chemistry, built in 1908, was o n e of th e first fire-p ro o f u n iv e r sity chem istry b uild ings in this cou n try. . . For instruction and re­

search in organic chemistry, Syracuse U niversity u ses M ultiple Unit O rganic Com bustion Furnaces.

SEND FOB B U L L E T IN H D -7 3 5

July 15, 1942 A N A L Y T I C A L E D I T I O N 5

OF F R E E D O M F R O M S L A V E R Y

L I N C O L N IS SU ED THE E M A N C I P A T I O N P R O C L A M A T I O N

KIMBLE cm! EXAX

GRADUATED GLASSWARE

KÍMBLE 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 • I N D I A N A P O L I S • S A N F R A N C I S C O 2 H i £ t h e p i o n e e r

L I N E

ATI O N S

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

SCIEN TIFIC TESTING EQUIPMENT

Photom eters

7X TLAS-OMETERS offer a simple, controllable method of reducing months of actual use conditions to just a few days testing. By accelerating the effect of sun, weather, and laundering, they determine, in your lab­

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ATLAS FADE-OMETER

The accepted standard for deter-

Ilk rra I I]

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sents closest approach to natural sunlight. Temperature automati­

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No. 900-3

F o r t h e v a rie d n e e d s o f i n d u s t r i a l , c lin ic a l a n d a g r i c u l t u r a l la b o r a to r ie s . C o m p le te a n d s e lf c o n t a i n e d '— n o a c c e s s o ry e q u i p ­ m e n t n e c e s s a ry . F u s e d c e lls fo r re a d in g s o n s o l u ti o n d e p th s o f 2.5, 10, 20, a n d 40 m m . S e le c tiv e li g h t f ilte rs a v a ila b le .

ATLAS LAUNDER-OMETER

S t a n d a r d laboratory washing machine of the A.A.T.C.C. Tests wash- - ^ S ^ ig r in g a c t i o n , t e xt i l e shrinking, staining, and color fastness to dry cleaning solvents, soaps and de­

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trolled—can be reproduced iden­

tically at any time.

ATLAS WEATHER-OMETER

Reproduces faithfully the de­

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tendant phenomena of expan­

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No. 2071

D e s ig n e d f o r t h e r a p i d a n d a c c u r a t e d e t e r m i n a t i o n o f

t h i a m i n , rib o fla v in , a n d o t h e r s u b s t a n c e s w h ic h flu o re s c e i n s o l u ti o n . T h e s e n s iti v it y a n d s t a ­ b i l i t y a r e s u c h t h a t i t h a s b e e n f o u n d p a r t i c u ­ la r ly u s e f u l i n d e t e r m i n i n g v e ry s m a l l a m o u n t s o f th e s e s u b s ta n c e s .

T o f u r t h e r in c r e a s e i t s a d a p t a b i l i t y a s e p a r a te c i r c u i t a n d s c a le is p ro v id e d f o r c o lo r im e tr ic d e t e r m i n a t i o n s .

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

ATLAS ELECTRIC DEVICES COMPANY

377 W. Superior Street, Chicago, Illinois

M an ufactu rin g Co.

179 E A S T 8 7 T H S T R E E T N E W Y O R K , N. Y-

July 15, 1942 A N A L Y T I C A L E D I T I O N 7

STANDARD for Gravimetric, Gasometric or Titrimetric Analysis

For purposes o f standardizatio n, C on gress, in 1838, directed the Secretary o f Treasury to furnish uniform b ala n ce s to each state in the Union. The 5 0 -p o u n d balance a n d t h e 2 5 - p o u n d b a l a n c e fu rnished are sh o w n here.

Standardized as carefully as official weights and measures, M allinckrodt A nalytical R eagents are refined to fixed and predetermined standards.

Upon em ptying one bottle o f a M allinckrodt A. R. Chemical the analyst can start a fresh one w ith certainty o f the same standards o f purity.

W hy not request a catalogue o f Mallinckrodt Analytical R eagents and other laboratory chemicals.

A LW A Y S SPECIFY REAGENTS IN MANUFACTURER'S O RIG IN A L PACKAGES

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

ST. LOUIS • PHILADELPHIA • MONTREAL

CHICAGO • NEW YORK * LOS ANGELES

8 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y

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ELECTROPLATING — as Simple as Painting

W i t h t h e " W ^gam & ⁱ " e l e c t r o p l a t e r P la te s W ith a B rush

Requires no skilled operator. Can be applied on specific areas w ithout expense and inconvenience o f plating w hole surface by im m ersion. Jelly-like com ­ pounds w ill not spill o r drip. Com pletely portable.

P lating done in any p osition w ithout dism antling.

H igh m etallic content o f com pounds elim inates neces­

sity for large anodes.

Perm its spot-plating various objects usually o f lim ited area. Plates only w here brush is applied. Quality o f plate equal to com m ercial platings o f equal thickness.

P lating deposited in less tim e than by com m ercial m ethods.

BA TTERY MODEL

(Illustrated)

I n c lu d e s îE le c tr ic P Ia tin g B ru sh es.

C o m p o u n d s fo r 8 0 0 sq . in ch es, each Silver, N ic k e l a n d C o p p e r, C le a n in g a n d P o lis h in g M aterials.

D e g re a s e r, a n d D ire c tio n s F o ld e r.

U ses fo u r IM

v o lt d ry _ c ells

* • 1 * 7 5

ELECTRIC MODEL

1 1 0 -1 2 0 v o lts a.c. 5 0 -6 0 cycle—

In c lu d e s 4 E lectric P latin g B ru sh es, C o m p o u n d s fo r 8 0 0 sq.

in ch es, e a c h S ilver, N ickel, C o p p e r, C ad m iu m , D eg reaser, C le a n in g a n d P o lis h in g M aterial, a n d C le a r L acq u er. In stru c tio n B o o k .

(n o t fu rn ish e d )

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July IS, 1942 A N A L Y T I C A L E D I T I O N

B & A A l l - A m e r i c a n Q u a n t i t a t i v e F i l t e r P a p e r

★

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B a k er & A d am son G rade “ 0 ” Q u a n tita tiv e F ilte r P a p er is 100% A m e rica n . . . m a d e in A m erica en tire ly o f d om estic m a teria ls. I t g iv es A m erica n ch em ists—

in in d u stry , in co lleg e s and sc h o o ls —fu ll assur­

ance o f a r e lia b le a n d c o n tin u o u s sou rce o f a high q u a lity q u a n tita tiv e filter p ap er!

L ike a ll B & A p ro d u c ts, G rad e “ 0 ” is d e p e n d ­ a ble— an o u tsta n d in g ex a m p le o f B ak er & Adam -

B & A GRADE “0 ” DOMESTI C QUANTITATIVE FILTER PAPER PROVIDES THESE FEATURES!

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C o d e N o . D iam e te r A s h in o n e p a p e r

2470 5Vi c.m. .00001 gra m s

2471 7 c.m. .00002 g ra m s

2472 9 c.m. .00003 gram s

2473 11 c.m. .00005 gram s

2474 12V4 c.m. .000065 gram s

2475 15 c.m. .000093 gram s

so n ’s efforts to serve th e A m erica n ch em ic a l in ­ d ustry b etter. S tu d y th e sp ecifica tio n s b e lo w . . . then w r ite to d a y for g en ero u s fr e e sam p les o f th is h igh grade p a p er. W h en y o u r e ceiv e y o u r sam ­ p le s, try them . N o te th e h ig h sp eed , h ig h re ten ­ tion , and h ig h s tr e n g th ! T h e n o rd e r y o u r r e q u ir e ­ m en ts as “ G rad e ‘0 | ‘lo w a sh ’ p a p e r !”

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10 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y

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

R E T A I L — W H O L E S A L E — E X P O R T

L A B O R A T O R Y A P P A R A T U S A N D R E A G E N T S V O N C Z O E R N I G - A L B E R

M ICRO C O M B U S T IO N FURNACE

A N D

C O N S T A N T T E M P E R A T U R E C H A M B E R ( H E A T I N G M O R T A R )

5686-A.

5677- F.

M I C R O C O M B U S T IO N F U R N A C E , E le c tr ic , v o n C z o e r n ig - A lb e r , A .H .T . C o. S p e c ific a tio n , c o m ­ p le te w ith S a m p le H e a t e r " A ” , f o r te m p e r a t u r e s u p t o 7 5 0 ° C . F o r e l e m e n ta r y q u a n t i t a t i v e o rg a n ic m ic ro a n a ly s is , in c lu d in g d e te r m in a tio n s fo r c a r b o n a n d h y d r o g e n , n itr o g e n b y t h e D u m a s m e th o d , h a lo ­ g e n s a n d s u lf u r b y t h e c a ta ly tic p r o c e d u re .

Provides uniform and constant temperatures within the ranges required for many types of micro tests sim-ply by changing the position of the tube in the furnace, but the use of transformer or rheostat is suggested for critical work or when the tempera­

ture m ust be changed gradually w ithout disturbing the tube.

The outside dimensions of the furnace body are 8 inches long X 2 '/ 2 inches deep X 2 1/« inches high, w ith chamber

8 inches long X l l/ie inches deep X ^{V j} inch high. The hinged front is of transite and can be raised w ith unprotected fingers by wire handle. Mounted on an adjustable stand with leveling screws and adjustm ent for centering and clamping combustion tubes. Furnace body can be moved laterally, either to right or left, on tracks lo l/ t inches long; also moved forward or backward for approximately 2 inches.

When operated w ithout a resistance and w ith tube placed against the rear wall of chamber, tem perature remains con­

sta n t a t 700 C to 730°C under normal voltage conditions. By moving the furnace so th a t tube is midway between the front and rear of the chamber, tem peratures between 670° and 700°C are obtainable. The lowest uniform tem peratures are directly back of th e hinged front where they are constant from 580° to 600°C. Constant tem peratures can be attained in approximately 30 minutes w ithout th e use of a resistance. Average life of the heating element, when used w ithout resis­

tance, is approximately 2000 hours. Maximum power consumption 3 amperes.

The Electric Sample H eater “A” is mounted on a carriage with rollers which fit th e tracks of the furnace support on either left or right end and replaces th e Bunsen type gas burner generally used to heat the sample in the combustion tube before it reaches the furnace. Cylindrical chamber is 75 mm long X 13 mm inside diameter, w ith heating unit made of carefully tested iron-free nichrome wire wound on a refractory core. Reproducible heating conditions are possible as the maximum tem perature of 750 to 800°C is uniform for a central zone of 45 mm w ithout th e use of transform er or rheostat.

Will reach 650°C in ten minutes and cools off to 200°C in approx. tw enty minutes. Three set screws provide centering ad­

justm ents and an insulated knob in front perm its lateral movement a t desired speed.

5677-F . M icro C o m b u stio n F u rn a c e , E lec tric , vo n C zo ern ig -A lb er, A. H . T . Co. S p ecification, as a b o v e describ ed , c o m p lete on a d ju s ta b le s ta n d w ith E lec tric Sam ple H e a te r “ A ” , c o n tin u o u sly v a ria b le tra n sfo rm e r, tw o s e ts of cords a n d plugs, a n d d e ta ile d d ire c tio n s fo r use.

F o r 115 v o lts, 50 to 60 cycles, a.c. o n ly ... 109.50 5677-G . D itto , b u t w ith rh e o s ta t in place of tra n sfo rm e r. F o r 115 v o lts, a .c. o r d .c . ... 105.00

CONSTANT TEMPERATURE CHAMBER (HEATING MORTAR), Electric, A. H . T. Co. Specification, heavy duty model, for controlling the tem perature of lead peroxide to obtain correct hydrogen values in micro carbon and hydrogen determinations w ithout the use of glass or organic liquids as required for th e original gas heated apparatus. Set for opera­

tion a t 175°C, constant to — 1.0°C, b u t with heating range adjustable from room tem perature to 200 °C.

Designed especially for use with above Combustion Furnace b u t usable with any micro carbon and hydrogen combus­

tion apparatus which meets the recommendations of the A. C. S. Committee on Standardization of Microchemical Ap­

paratus.

C o n sistin g of c a s t a lu m in u m block w ith h o riz o n ta l c h am b er a n d e m b e d d ed 1 2 5 -w att, c a rtrid g e -ty p e h e a tin g u n it a n d th e rm o -re g u lato r, enclosed in m e ta l cage on b ase w ith 1-inch v e rtic a l a d ju s tm e n t. C h a m b e r is 70 m m lo n g X 15 m m in sid e d ia m e te r, re d u c ed a t one e n d to 5.5 m m b y m ean s of a h a rd asb esto s en dpiece w h ich s u p p o rts th e co m b u stio n tu b e . O v erall dim en sio n s w ith o u t th e rm o m e te r, 3 l/< in ch es w ide X 5 in ch es d eep X 101/» inches high.

5686-A . C o n sta n t T e m p e ra tu re C h am b er (H e a tin g M o rta r), E lec tric , A. H . T . Co. Specificatio n , as a b o v e describ ed , w ith sp ecial th e rm o m e te r 150 to 2 0 0 °C in 1° d ivisions, p ilo t la m p , h e a tin g ro d , 70 m m lo n g X 4 m m d ia m e te r, sn a p sw itch , co n n ec tin g c o rd a n d plug, and d irectio n s fo r u se. F o r 115 v o lts, a .c. o n ly ... 40.00 5686-B . D itto , b u t for 115 v o lts, d .c ... 41.25

M ore d e ta ile d in fo r m a tio n s e n t u p o n re q u e st.

W E S T W A S H IN G T O N S Q U A R E , P H IL A D E L P H IA , U . S. A.

C a b le A d d re ss, “ B a la n c e ,” P h ila d e lp h ia

INDUSTRIAL ^{a n d} ENGINEERING CHEMISTRY

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

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

Field Testing o f Mold-Resistant Properties^

o f Interior Oil Paints ( politechnik !!

A L E X M . P A R T A N S K Y

B io c h e m ic a l R e s e a rc h L a b o r a to r y , T h e Dow C h c in ic a l C o m p a n y , M id la n d , M ic h .

T

H E o bject of th e p rese n t pap er is to discuss th e problem s involved in te stin g m old-resistant properties of interior oil paints in th e field an d to describe th e a u th o r’s experience in such work.

T he previously reported (12) la boratory m ethod for deter­

mining m old resistance of oil p ain ts affords a rap id and con­

venient w ay for ev aluating th e relative effectiveness of toxicants u n d er th e readily reproducible standardized con­

ditions. H ow ever, such effectiveness against fungi is only the first prerequisite for a good p a in t preservative. In addition, it should be stable, n o t affect th e physical or chemi­

cal properties of th e p ain t, and be effective u n d er th e condi­

tions of actual use over a fairly long period of tim e (2, 8,14) ■ I n other words, afte r a quick elim ination of ineffective p repa­

rations b y th e la b o ra to ry m ethod, th e selected com pounds should be subjected to a fu rth e r testin g “ in th e field” .

T he mold resistance of outside oil p ain ts tested b y exposing wooden panels in localities w here th e prev alen t n atu ra l condi­

tions are conducive to m old grow th (such as certain p a rts of Florida, Louisiana, C uba, an d th e P an am a C anal Zone) has been previously reported b y various investigators (1 ,4 , 5 ,6 ) . However, no system atic s tu d y of th e m old-resistant properties

of interior oil p aints u nder conditions sim ilar to those of ac tu a l use could be found in th e literatu re.

As a prelim inary step for th e investigation, a survey of th e occurrence of mold grow th on p a in t a t different ty p e s of indus­

tria l p la n ts was m ade in th e m idw estern an d eastern sta te s.

R esults of this survey, supplem ented b y subsequent experi­

ence during th e ac tu a l testin g of fungicidal p ain ts, gave th e following p icture of th e occurrence and cause of m old grow th on interior p a in ts :

1. Generally speaking, the prevalence of mold growth on in­

terior painted surfaces (walls, ceilings, window sash, etc.) in the various industrial plants examined was much greater than was originally anticipated. Occurrence of mildew was particularly common in industries where, owing to the nature of th e processes involved, a high relative hum idity was maintained.

2. In many of the food-processing and packing establishments, such as m alt houses, breweries, distilleries, m eat and vegetable packing houses, bakeries, and dairies, and in cheese, b utter, m ar­

garine, pickle, and similar plants, in addition to having high rela­

tive humidity, the air also frequently carries dust and w ater spray and vapors containing organic m atter. The latter m ate­

rials when deposited or adsorbed on the walls and other surfaces provide most favorable conditions for the development of mil­

dew (9, IS, 14).

Left.

Right.

FiG U H E 1 . Ty p i c a l Mo l d Gr o w t h s re p a ir

¡oloniei

527

U n u su ally h e a v y g ro w th on wall an d pipes re p a in te d less th a n a y e a r p rio r to tim e p ic tu re was ta k e n In te rio r oil p a in t, show ing fu z iy circu lar colonies

&

<a

2 3 2 4 Z o I S &

u.^~ - 2 ^

Fi g u r e 3 . Ge n e r a l Vi e w o f Te s t Ar e a a f t e r Ei g h t Mo n t h s

N o te g ra d a tio n in in te n s ity of m old g ro w th o n N o . 10, u n tre a te d p a in t, a n d c o m p lete ab sen ce of m ildew on p an els 12, 22, a n d 26.

tions of the walls near the ceiling have, as a rule, a much heavier mold growth than the lower parts of the walls (Figure 3).

Probably because of the difference in air circulation, corners of the rooms, usually, have more mold growth than the adjacent open wall space.

In selecting a location for testin g m old resistance of interior paints, all th e above factors should be ta k e n into considera­

tion. Since in indoor testin g th e conditions conducive to m ildew do n ot, as a rule, v a ry m uch from y ea r to year in any one given place, th e in te n sity an d u niform ity of m old growth on p a in t from th e previous year are one of th e b est guides in choosing th e area for th e te st.

T he uniform ity of th e conditions th ro u g h o u t th e te s t area is p articu larly im p o rta n t, since usually only th e relative values, such as a com parison betw een th e tre a te d an d th e u n tre a te d p ain t, are desired. As a fu rth e r precaution, in a series of te s t panels every fo u rth or fifth panel should be painted w ith an u n tre a te d p ain t. T h e absence of mold grow th on fungicidal p a in t is considered as a proof of its mold resistance only w hen th e u n tre a te d p a in t panels in th e same series show a fair a m o u n t of m olding. T h e te s t p ain ts are best applied to th e selected areas during th e season when the surfaces to be p ain ted are driest.

F ro m w hat has been said on th e im portance of m oisture condensation on th e surface, it is a p p a re n t th a t th e te s t paint should be applied directly to th e walls a n d ceiling of th e build­

ing ra th e r th a n to th e sep arate panels. T his fac t has been verified b y th e parallel use of wooden panels an d d irec t paint­

ing on ceiling an d walls. I n all cases, m olding of th e corre­

sponding u n tre a te d or insufficiently preserved p a in ts was less severe on th e wooden panels th a n on th e walls.

A ty p ic al experim ent in te stin g m old-resistant properties of in terio r oil p ain ts tre a te d w ith a selected group of fungicidal agents u n d er ac tu a l conditions of usage w as as follows:

The 6 X 30 foot test area selected was on the interior of the northern brick wall in a relatively old grain-processing plant in the Middle West. I t was located under the fresh-air intake, and a t the time of selection had the greatest am ount of mildew found anywhere in the plant. For many years previously the walls and ceiling of the building had been whitewashed during the annual summer clean-up period, but in the past 4 years the practice was changed to painting the walls with oil paints and the ceiling with a water-cement paint. The te st area was prepared for painting I N D U S T R I A L A N D E N G

Fi g u r e 2 . Di f f e r e n c e i n Mo l d In f e s t a t i o n O u tsid e w all a t b ack , in te rio r p a rtitio n a t left. S ig n ifican t g ra d a ­

tio n in in te n s ity of m old g ro w th on ceiling

3. Mold growth on painted interior surfaces usually manifests itself as black and less frequently as green or red discoloration (1, 11). Although this discoloration is sometimes mistaken by the layman for dirt, the mold growth can be readily distinguished from dirt by the fact th a t it is usually patchy or blotchy and con­

sists of circular, spreading, and somewnat fuzzy spots (Figure 1).

4. Mold infestation of the painted surfaces is seldom uniform and depends on the local variations in two im portant factors—

moisture content of the paint film and relative hum idity of the atmosphere. The following examples illustrate this:

The inner side of a cold outside wall of a building on which moisture is condensing is more ap t to have mildew than the inner side of a warmer wall or the interior partitions (Figure 2). For this reason heavier mold growth can be expected during the cold winter months.

F or the same reason (moisture condensation), ceilings and por­

July 15, 1942 A N A L Y T I C A L E D I T I O N 529

Fi g u r e 4 . Cl o s e- Up o f Ty p i c a l Se c t i o n sa f t e r Ei g h t Mo n t h s’ Ex p o s u r e 10, 11, 12. P a in te d w ith m ill w hite p a in t 20, 22, 26, 27. P a in te d w ith gloss p a in t 10. U n tre a te d p a in t 20. U n tre a te d p a in t

11. 1.5 p er c e n t tetra c h lo ro p h e n o l 22. 3 p e r c e n t tetra c h lo ro p h e n o l 12. 3 p e r c en t tetra c h lo ro p h e n o l 26. 3 p er c e n t zinc te tra c h lo ro p h e n a te

27. 0.63 p er c e n t calom el

in the usual way—th a t is, it was scrubbed with soap and phos- phate-softened w ater using a stiff brush, rinsed with fresh water, and the old loose paint was scraped off with a p u tty knife. The test area was divided into 25 sections, each approximately 12 inches wide and extending 76 inches downward from the ceiling;

two coats of test paint were applied. The painting was done in August, 1939, during the summer shut-down when the walls were dry; the plant started operation 2 weeks later.

The paints used were as follows:

Paints 10 to 15 were made up from a widely used flat mill white paint with heat-bodied linseed oil vehicle.

Paints 20 to 27 were made up from a typical interior gloss white paint of a cold-cut D ainar resin type.

These paints were treated with preservatives as follows (all percentages are on the original paint weight basis):

Nos. 10 and 20, controls, without preservatives Nos. 11 and 21, with 1.5 per cent tetrachlorophenol Nos. 12 and 22, with 3 per cent tetrachlorophenol Nos. 13 and 23, with 1.5 per cent lead tetrachlorophenate Nos. 14 and 24, with 3 per cent lead tetrachlorophenate No. 25, with 1.5 per cent zinc tetrachlorophenate No. 15, with 2.5 per cent zinc tetrachlorophenate No. 26, with 3 per cent zinc tetrachlorophenate

No. 27, with 6.3 volume per cent (manufacturer’s recommen­

dation) of a commercial antimildew paste containing 8 per cent (by weight) of calomel, giving a total of 0.63 per cent calomel by weight of the total paint, or 3.5 per cent calomel by weight of the nonvolatile portion of the vehicle.

Periodic exam ination of th e te s t area showed practically complete absence of m ildew during th e first 3 m onths. How­

ever, w ith th e ad v e n t of cold w eather, when m oisture con­

densation on th e wall k e p t th e p ain t surface continuously wet, th e mold grow th began to m ake its appearance.

The original u n tre a te d paints, 10 and 20, and th e calomel- containing p ain t, 27, were th e first to show m old growth.

Paints 13 and 23 w ith 1.5 p er cen t of lead tetrachlorophenate were next, an d 8 m o n th s later, on April 3, 1940, when photo­

graphs shown in F igures 3 and 4 were taken, a sm all am ount of mold grow th was also noted on p ain t 21 (gloss white with 1-5 per cent tetrachlorophenol). A t th e same tim e, all paints

containing 3 per cent of toxicants an d th e mill w hite p a in t containing 1.5 per cent tetrachlorophenol were still mold-free.

In all cases th e mold grow th sta rte d on th e upper end (near th e ceiling) of th e te s t sections and w ith tim e gradually spread downward (Figure 3). T he sam e photograph gives th e general view of th e setu p and th e appearance of a p a r t of th e te st area and th e surroundings a t th a t tim e. N o te p a rtic u ­ larly th e severity of mold infestation of th e ceiling (painted w ith a cem ent pain t) and th e v ery interesting g rad atio n in th e in ten sity of mold grow th on section 10. Close-ups of th e upper portions of th e tw o sets of typical te st sections are given in F igure 4.

T he next set of photographs was tak en on A ugust 26, 1940, afte r one year of exposure. B y th a t tim e th e p la n t h ad been sh u t down for cleaning an d redecoration; th u s, th e walls had already been repainted w ith an oil p a in t and th e ceiling sprayed w ith a cem ent-w ater p ain t. T hese operations re­

sulted in some dam age to th e te s t area, b o th from th e w ater during cleaning and from th e spraying of th e cem ent p ain t.

In addition to this, d irt accum ulation from A pril to A ugust was ra th e r severe. T he general view of th e te s t area, p hoto­

graphed after a lig h t washing w ith w ater to rem ove surface dirt, is shown in F igure 5. T he p ain ts containing te tra ­ chlorophenol (except for th e u pper portions of th e sections sp lattered w ith th e cem ent pain t) washed p ractically clean, indicating th a t th eir original d a rk color was due prim arily either to th e surface d irt o r to th e loose readily w ashable mold grow th on th e d irt film. In c o n tra st to this, th e m old growth on th e u n trea ted p ain t, N o. 10, could n o t be washed off w ith th e sam e effort, indicating th a t in th is case th e mildew' had grown into th e p a in t itself.

T he above-described te s t a re a was allowed to rem ain un ­ disturbed for another year. D uring th e second season d irt deposition on th e walls was again heavy. T he general view of th e te s t area, tak en J u ly 15, 1941, a fte r a lig h t washing,

10 or 20, and the other half of each with treated paints (same as previously listed). Two coats of each paint were applied a t the laboratory, and in addition one set of panels received a third coat of paint applied on the location ju st before the panels were exposed. The wooden panels were hung on the wall near the ceiling in the same room and just east of the test area de­

scribed above.

Fi g u r e 5 . Ge n e r a l Vie w7 o f Pa r t o f Te s t Se c t i o n ( On e- Ye a r Ex p o s u r e) a f t e r Wa s h i n g

(Figure 6, above), shows th a t a fte r two y ears’ exposure th e general distrib u tio n of m old grow th was ab o u t th e sam e as a fte r th e first year. T h e sections p ain ted w ith flat mill white p a in t washed alm ost to th e ir original w hiteness, while th e gloss paint, b o th tre a te d and u n tre a te d , acquired a g ray cast, m aking it im possible to wash it clean.

In May, 1939, two sets of 12 X 24 X 0.5 inch white pine panels were prepared in the laboratory, in which one half (6 X 24 inch areas) of each panel was painted with the untreated paints, No.

A fter one season’s exposure, in contrast w ith th e wall tests, only a sm all am o u n t of m old grow th could be seen on an y of the wooden panels. However, a fte r th e second year, panel sections painted w ith u n treated flat mill w hite p a in t developed considerable mold growth, while on th e trea ted p ain ts the grow th was sm all or absent. P hotograph of th e back side (tow ard th e wall) of these panels is given in F igure 6 (below). T h e fro n ts id e of th e panels (tow ard th e room ) accum ulated too m uch d ir t for th e observation to be of value. T h e 2-year results w ith th e flat mill w hite p ain ts on wooden panels were in good agreem ent w ith those obtained w ith th e wall tests T he gloss p a in t on th e wooden panels of th e sam e se t molded b u t lightly except in places where d irt accum ulation was considerable. T here was no difference in m old grow th be­

tw een th e tw o-coat and th e three-coat panels (the th ird coat of which was applied on th e location).

T h e difference in th e results obtained w ith th e wooden panels and th e p ain ted wall area, a fte r one season’s exposure, is accounted for b y th e difference in m oisture condensation

Above.

Below.

Fi g u r e 6 . Pa n e l s a f t e r Tw o- Ye a r Ex p o s u r e

G e n eral view of te a t a re a a fte r w ashing. N o te clearness of N os. 11 a n d 12, c o n ta in in g te tra c h lo ro p h e n o l in m ill w h ite.

B a c k side of " h a lf a n d h a lf” w ooden panel*. L e ft-h a n d p o rtio n of each w as p a in te d w ith u n tre a te d p a in t, N o . 10.

July 15, 1942 A N A L Y T I C A L E D I T I O N 531 on th e surfaces. A nother contributing factor m ight be th a t

th e wood used in th e panels was new, while th e painted wall area h ad a previous mold grow th. T his mold growth, al­

though partially scraped an d washed off in preparing th e surface for repainting, nevertheless provided a ready-m ade source of m old infection for th e new paint. A considerable volume of evidence is now a t h and which suggests th a t under favorable conditions certain types of mold growth, when painted over, can and will come through a nontoxic p ain t film. T his has also been pointed o u t by F indlay (1).

F o r th e above reason, cleaning and disinfection of old m oldy surfaces prior to repainting are im p o rta n t and should be m ade a p a r t of th e repainting procedure (1, 7 ,8 ,1 0 ). This contention is confirmed b y actual te sts in which identical paints were applied to a contam inated area, one half of which was first washed w ith a d isinfectant solution while th e other half was not.

S u m m a ry a n d C on clu sio n s

M old grow th on interior oil p ain ts is com mon in industrial plants where a high relative h u m id ity is m aintained.

T he m old grow th is never uniform even in an y one room, b u t is heaviest on surfaces where m oisture condensation takes place, such as th e in terior side of cold outside walls, locations near refrigeration pipes, ceilings, etc.

Organic m a tte r, vapors, and d u st are conducive to mold growth b u t interfere som ew hat w ith th e testing of th e mold- resistan t properties of paints. However, where mold growth develops on th e d u st deposited over an oil paint, a preserved p ain t can be relatively easily washed clean, while on a non- fungistatic p a in t th e m old grow th becomes established in the p ain t itself and cannot be washed off.

M old resistance of interior paints should be tested by ap­

plying th e te s t p ain ts to carefully selected sections of walls and ceiling on which w ater condensation is continuously taking place and which are found to be th e m ost heavily con­

tam inated areas in th e p la n t selected. T h e use of wooden panels, even w hen m ost advantageously exposed, m a y give erroneous results due to th e difference in conditions betw een them and th e painted surfaces of th e building.

In preparing m oldy surfaces for repainting, disinfection of th e cleaned surface is beneficial, since some m olds can grow th rough a p a in t film.

W ith o u t an adeq u ate preservative th e p a in t w ith a cold- c u t resin type of vehicle m olded as readily as th e p a in t w ith a vegetable oil ty p e of vehicle.

Tetrachlorophenol and zinc tetrach lo ro p h en ate were found to be th e m ost effective p a in t preservatives am ong those tested.

U nder extrem ely severe conditions of testin g 3 per cen t of tetrachlorophenol and 3 per cent of zinc tetrachlorophenate preserved b o th an oil and a cold-cut resin ty p e of interior p ain t for 2 years.

T he field te s t confirmed earlier conclusions on th e relative effectiveness of fungicides in oil p ain ts as determ ined by th e rap id la boratory m ethod.

L itera tu re C ited

(1) Findlay, W. P. K., J . Oil Colour Chem. Assoc., 23, 217 (1940).

(2) Findlay, W. P. K., Paint Varnish Production Mgr., 21, 135 (May, 1941).

(3) Ibid., 21, 194 (July, 1941).

(4) Gardner. H. A., H art, L. P., and Sward, G. G., Am. P ain t Var­

nish Mfrs. Assoc., Sci. Circ. 442, 242 (1933).

(5) Ibid., 448, 11 (1934).

(0) Ibid., 464, 135 (1934).

(7) I b id .,ilS . 1 (1935).

(8) Hansen, C., Paint Varnish Production Mgr., 20, 146 (1940).

(9) H arry, R. G., Paint M anuf., 6, 309 (1936).

(10) Hofmann, W. F., Am . Paint J ., 22, 22, 58 (1938).

(11) Ludwig, W., Rev. Applied Mycol., 19, 719 (1940).

(12) Partansky, A. M „ and McPherson, It. It., In d. En o. Ch e m.,

Anal. Ed., 12, 443 (1940).

(13) Toch, M., Am. Soc. Bakery Engrs., Bull. 103 (1936).

(14> Weise, K ., Farben-Ztg., 39, 412, 444 (1934).

Determ ination o f Small Amounts o f Benzene in the Presence o f Cyclohexane

A nd o f T olu en e in the P resen ce o f M ethylcyclohexane

B . B . C O R S O N A N D L . J . B RA D Y , M e llo n I n s t i t u t e , P i t t s b u r g h , P e n n a .

T

H E m ethod described in th is paper consists in m easuring th e tem p eratu re rise (AT1) caused by th e interaction of benzene or toluene w ith n itra tin g acid under definite con­

ditions, an d reading th e percentage of arom atic from a curve relating A T w ith hydrocarbon com position. Benzene, up to 12 per cent, can be determ ined b y this em pirical m ethod w ithout diluting th e sam ple. F or higher concentrations th e sample m u st be diluted w ith cyclohexane, so th a t A T will not exceed 20° C.

This therm om etric m ethod, w hich depends specifically upon th e h ea t of reaction of benzene w ith n itra tin g acid, is espe­

cially suitable for th e analysis of benzene-cyclohexane mix­

tures resulting from th e hydrogenation of benzene. A naly­

sis by refractive index or density is unreliable, owing to th e fact th a t cyclohexane is usually contam inated w ith m ethyl- cyclopentane (1) (C«Hn: n2£ 1.4264, d$° 0.7781; C H³C⁵H⁹: n3S 1.4099, d f 0.7488). Also, open-chain paraffins often con­

tam inate benzene an d th e cyclohexane produced from it.

T he therm om etric m ethod gives results w hich are a t least as

accurate as those obtained from freezing p o in t d a ta . I n th e analysis of a series of sy n th etic benzene-cyclohexane m ix­

tures, in w hich th e benzene concentrations varied from 0 to 12 per cent, th e average deviation from th e m ean was 0.06 per cent.

T he therm om etric m ethod works equally well w ith toluene- m ethylcyclohexane m ixtures; b u t in th e case of xylene- dim ethylcyclohexane m ixtures A T is dependent upon th e isomeric com position of th e xylene, an d therefore, th e rela­

tionship betw een A T and arom atic co n ten t m u st be deter­

m ined for each sam ple of xylene in question.

D e v elo p m en t o f M e th o d

T h e variables of acid stren g th , period of stirring, w ate r con­

te n t, size of stirrer, initial tem p eratu re, an d change of AT w ith tim e have been studied.

The procedure was to add 50 cc. of a mixture of benzene and cyclohexane (containing 5.2 per cent of benzene) to 100 cc. of nitrating acid contained in a small-necked pint thermos bottle

4 6 S 10 12 14 M i n u t e s o f S t i r r i n g

Fi g u r e 2 . Va r i a t i o n i n Fi n a l A T w i t h Ti m e o f St i r r i n g

6 12 IB

M i nu t e s

Fi g u r e 1. Va r i a t i o n i n A T w i t h Co m p o s i t i o n o f Ac id

B ro k en lines, te m p e ra tu re d u rin g stirrin g period Solid lines, te m p e ra tu re a fte r s tirrin g p eriod

whose metal collar was coated with paraffin to protect it against the acid. Both solutions, acid and hydrocarbon, were initially a t room temperature, as was the thermos bottle. After stirring for different lengths of time, the stirring was stopped, and the tem perature of the acid-hydrocarbon mixture was measured with a 50° thermometer graduated in 0.1° C.

Ef f e c t o f St r e n g t h o f Ni t r a t i n g Ac i d. N itra tin g acid containing 1 volum e of nitric acid (density 1.5) and 1 volum e of sulfuric acid (density 1.84) was unsatisfactory, for A T continued to increase long afte r th e stirring had been stopped (Figure 1), owing to slow de-em ulsification of th e acid-hydro­

carbon m ixture. O nly 40 cc. of hydrocarbon w ere used w ith this acid because 50 cc. of hydrocarbon raised th e tem p era­

tu re to such an ex ten t th a t th e n itric acid rap id ly decom ­ posed. T h e finally accepted n itra tin g acid contained 2 vol­

umes of n itric acid (density 1.42) an d 1 volum e of sulfuric acid (density 1.84). T his acid gave a definite end point w ith a sufficiently large A T . N itric acid alone (density 1.42) yielded a A T of only 2 ° C., whereas mixed acid containing one th ird as m uch nitric acid produced a A T of 8.5° C.

(Figure 1).

Ef f e c t o f St i r r i n g Pe r i o d. Figure 2 shows th e effect of varying th e length of th e stirring period. T h e mixed acid contained 2 volum es of n itric acid (density 1.42) an d 1 vol­

um e of sulfuric acid (density 1.84). T he A T w as recorded 10 m inutes a fte r th e end of th e stirring period. E vid en tly th e length of th e stirring period is critical up to 9 m inutes, b u t a fte r 9 m inutes A T is essentially independent of small changes in th e stirring tim e { A T /t being 0.03° C. per m inute, which corresponds to an an alytical u n ce rtain ty of less th a n 0.02 per cen t of benzene per m inute).

Ef f e c t o f Wa t e r. A m ixture of 5.2 per cent of benzene an d 94.S per cen t of eyclohexane w as analyzed after drying, an d also afte r sa tu ra tin g w ith w ater. T he A T of th e dry sam ple w as 0.1° C. lower th a n th a t of th e w et sam ple. W et cyclohexane gave th e sam e A T as d ry cyclohexane (0.1° C.).

I t is recom m ended th a t th e hydrocarbon u nder exam ination be dried b y anhydrous calcium chloride before analysis.

Ef f e c t o f St i r r e r. T he recom m ended stirre r is a glass rod, 7 m m . in outside diam eter a n d 24 cm. long, w ith a flat­

tened end ± 13 m m . wide X 19 m m . long (Figure 3); i t is

H N Ojtd. 1.42)

operated by a 3000 r. p. m. electric m otor. Using a stirrer w ith a blade twice as large raised A T by 0.3° C. w ith a ben- zene-cyclohexane m ixture containing 5.2 per cent of benzene, a n d this difference corresponds to an ap p a ren t increase in the benzene content of ab o u t 0.2 per cent.

Ef f e c t o f In i t i a l Te m p e r a t u r e. I t is t o b e n o t e d t h a t A T f o r t h e r e a c t i o n o f b e n z e n e w i t h n i t r i c a c i d is g r e a t e r a t 20° C. t h a n a t 30° C., w h i c h is o p p o s i t e t o t h e t h e r m o d y n a m i c prediction, because = A(7P, and ACP is negative.

( c t i )p

T he effect is less w ith toluene-m ethvlcyclohexane, b u t is in the

[2 Vol. H N O s ( d . 1. 42 ) 1 l Vol. H , S O , Id. 1.84)

Fi g u r e 3 . Eq u i p m e n t f o r Ac i d He a t T e s t I Vol. H N O , (d. 1.5)

I Vol. H, SO„ Id.

Wf. */• Of B e n z e n e

Fi g u r e 4 . Ac i d He a t Te s t Da t a f o r Be n z e n e- Cy c l o- HEXANE

In itia l te m p e ra tu re , 2 0 °, 2 5 °, and 30° C.

same direction. P resum ably this anom alous relationship of A T to initial tem p eratu re is a ttrib u ta b le to th e relative speeds of dém ulsification a t th e different tem peratures.

P u r i t y o f H y d r o c a r b o n s . T he benzene was of reagent quality; th e cyclohexane w as m ade from it by catalytic hydrogenation under pressure a t ab o u t 135° C. T he cyclo­

hexane was shaken w ith n itra tin g acid, washed w ith w ater, and distilled. I ts freezing p o in t of 5.9° C. indicated a p urity of 99.7 per cent.

Ta b l e I. Ac i d He a t Te s t Da t a f o r Be n z e n e- Cy c l o i i e x a n e ( Fi g u r e 4 )

W eight

P ercen tag e AT from In itia l T e m p e ra tu re s of

of B enzene 20° C. 25° C. 30° C.

0.00 0 .1 0 0 .1 0 0 .1 0

0 .5 6 1 .1 0 1.1 0 1 .0 9

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

1 .5 6 2 .8 7 2 .7 9 2 .7 0

3 .2 9 5 .5 9 5 .4 0 5 .2 2

6 .3 8 1 0 .8 2 10.4 4 10.07

10.15 1 7 .1 3 16.55 16.0 0

12.01 2 0 .1 3 19.44 18.7 5

Ta b l e II. Ac id I Ie a t Te s t Da t a f o r To l u e n e- Me t h y l- c y c l o h e x a n e ( Fi g u r e 5 )

W eig h t

P ercentage of A T from In itia l T e m p e ra tu re s of

of T oluene 20° C. 2 5 ' C. 3 0 “ U.

0.00 ^{0 .3 2 0 .3 2 0 .3 2}

1 .34 3.9G 3 .9 5 3 .9 5

3 .5 0 9 .7 1 9 -6 4 9 .5 8

5 .4 9 1 5 .0 0 14.8 9 14 .8 0

D e te r m in a tio n o f B en zen e in C yclohexane

One hundred cubic centimeters of nitrating acid (1 volume of sulfuric acid, d. 1 .8 4 . plus 2 volumes of nitric acid, d. 1.42), measured in a 100-cc. volumetric flask, are poured into a thermos bottle, the-flask being allowed to drain 15 seconds. The ther­

mometer is placed in the thermos, the bulb resting on the bot­

tom of the latter, and the tem perature is read after 2 to 3 min­

utes (with a magnifying lens). Fifty cubic centimeters of hydro­

carbon sample (measured in a 50-cc. volumetric flask and at the same tem perature as the acid) are added to the acid in the ther­

mos. An interval tim er is started and the flask is allowed to drain 15 seconds.

The stirrer is placed in the thermos, w ith the bottom of the stirring blade about 1.25 cm. (0.5 inch) from the bottom of the thermos, and when the tim er reaches 30 seconds the motor is started. The stirrer is run 9.5 minutes and then removed from

Wt. % o f T o l u e n e

Fi g u r e 5 . Ac i d He a t Te s t Da t a f o r To l u e n e- He x a- HYDROTOLUENE

In itia l te m p e ra tu re , 2 0 °, 2 5 °, a n d 30° C.

the mixture. The thermometer is placed in the thermos (bulb resting on bottom of thermos) and the tem perature is read 10 minutes after stopping the stirrci^-i. e., 20 minutes after the addi­

tion of the hydrocarbon. The mixture is not shaken nor stirred during the last 10 minutes.

For precise work, not only should the acid and hydrocarbon be therm ostatcd to the same temperature, b u t the thermos bottle should also be a t th a t tem perature (although its heat capacity is small).

T he benzene content is read from th e fam ily of curves cor­

responding to th e d a ta in T able I, an d it is to be noted th a t A T is essentially independent of th e initial tem p eratu re

(20° to 30° C.) up to 1.5 per cent of benzene.

T able I I presents acid h e a t d a ta for toluene-m ethylcyclo- hexane m ixtures.

L itera tu re C ited

(1) Seyer, Wright, and Bell, Ind. Eno. Chem., 31, 759-60 (1939).

Co n t r i b u t i o n fro m th e K o p p ers M u ltip le Fellow ship on T a r S y n th e tic s, M ellon In s titu te , P ittsb u rg h , P e n n a .

Cleaning P o rcela in C rucibles

JO H N E. D. CARWARDINE 55 D o n ald S t., W in n ip eg , M a n ito b a , C a n a d a

T

H E m ethod described here can save considerable tim e a n d confusion b y cleaning “ burner grim e” a n d m arking inks such as ferric chloride from porcelain crucibles. I t does n o t injure th e glaze in a n y m anner, b u t leaves th e crucible w ith a perfectly clean surface.

P lace th e crucible in a dish of fused potassium bisulfate for ab o u t 5 m inutes. Rem ove, allow to cool, an d wash w ith h o t w ater.

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