Industrial and Engineering Chemistry : analytical edition, Vol. 12, No. 8

INDUSTRIAL a n d ENGINEERING CHEMISTRY

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

H A R R IS O N E. HOWE, E D I T O R » ISS U ED A U G U S T 15, 1940 » V O L . 12, NO. 8 « C O N S E C U T I V E NO. 16

Te s t i n g Mo l d- Re s i s t a n t Pr o p e r t i e s o f Oi l Pa i n t s

Alex M. Partansky and Robert R. McPherson 443

Cr i t i c a l So l u t i o n Te m p e r a t u r e s a n d An i l i n e Po in t s o f So m e Bu t a n e Hy d r o c a r b o n s...

Clifford G. Ludeman 446

C o l o r i m e t r i c D e t e r m i n a t i o n o f I r o n w i t h S a l i c y l - a l d o x i m e ... D . E . Howe with M. G. Mellon 448

De t e r m i n a t i o n o f Cr u d e Fi b e r...

A. M. Neubert, Fred VanAmburgh, and J. L. St. John 451

T e s t f o r R e s i d u a l C h l o r i n e ...F. J. Hallinan 452

A n a l y s i s o f B l a c k E n a m e l s . . . . S . E . Berkenblit 453

I r o n C o n t e n t o f B r e a d a n d B r e a d I n g r e d i e n t s . . .

Charles Hoffman, T. R. Schweitzer, and Gaston Dalby 454

C o l o r i m e t r i c D e t e r m i n a t i o n o f C o p p e r w i t h T r i - e t h a n o l a m i n e . John H. Yoe and Charles J. Barton 456

Id e n t i f i c a t i o n o f Al c o h o l s b y Me a n s o f Op t ic a l Pr o p e r t i e so f Es t e r s o f Ca r b a n i l i c Ac id . . . .

Bartlett T. Dewey and Norman F. Witt 459

Me t h o d f o r An a l y s i s o f Bo il e r Sc a l e sa n d Sl u d g e s

F. K. Lindsay and R. G. Bielenberg 460

Re d u c t i o n o f 2 - Na p h t h o l- Az o x y l e n e...

William Seaman, A. R. Norton, and J. Hugonet 464

W i j s I o d i n e M e t h o d ...J. W. McCutcheon 465

K i n e m a t i c V i s c o m e t e r f o r L i q u i d A s p h a l t i c P r o d ­ u c t s . A. P . Anderson, K . A . Wright, and R . L . Griffin 466

La r g e Sp i n n i n g- Ba n d Fr a c t io n a t in g Co l u m n f o r Us e w i t h Sm a l l Qu a n t i t i e s o f Li q u i d s...

Robert H. Baker, Chas. Barkenbus, and C. A. Roswell 468

T he American Chemical Society assumes no responsibility for the 22,700 copies of this issue printed.

Su c t io n Fi l t r a t i o n Ap p a r a t u s f o r Sa m p l i n g Fil­ t r a t e s u n d e r Co n s t a n t Pr e s s u r e...

Edward T. Fukunaga and L. A. Dean 471

A c c u r a t e T i m i n g E q u i p m e n t f o r V i s c o s i t y D e t e r ­ m i n a t i o n s . E . M . Fry, Jr., and E. L . Baldeschwieler 472

N e w D e s i g n o f C o m b u s t i o n B o a t T o n g s . H. F. Priest 473

Re s e a r c hi n Or g a n o m e t a l l ic Pr o b l e m s...

W. L. Gilliland 474

Va c u u m Tu b e Vo l t m e t e r...

Lloyd E. West with Rex J. Robinson 476

Me a s u r i n g Av e r a g e Pa r t ic l e Di a m e t e r o f Po w d e r s

Ernest L. Gooden and Charles M. Smith 479

Ap p a r a t u s f o r Ma i n t a i n i n g Co n s t a n t Le v e l s in Wa t e r Ba t h a n d Di s t i l l i n g Fl a s k...

Frederic E. Holmes 483

Un i v e r s a l pH Me t e r a n d Si m p l i f i e d Va c u u m Tu b e E l e c t r o m e t e r ...Frank M . Goyan,

Clifford L. Barnes, and Harry W. Hind 485

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

De t e r m i n a t i o n o f Zin c i n Pl a n t Ma t e r i a l s Us i n g Dr o p p i n g Me r c u r y El e c t r o d e . . . ...

J. Fielding Reed and Ralph W. Cummings 489

M i c r o s c o p i c M e t h o d f o r P o r t l a n d C e m e n t i n D u s t S a m p l e s ...Irwin A . Pearl 492

Mi c r o d e t e r m i n a t i o no f Ca r b o na n d Hy d r o g e n . .

Ralph 0. Clark and Gordon H. Stillson 494

Qu a l i t a t i v e Id e n t i f i c a t i o n o f Fe r r o c y a n i d e Io n

W. C. Oelke 498

ents and opinions advanced by contributors to its publications.

C opyright 1940 b y American C hem ical Society.

P u b lic a tio n O ffice: E a sto n , P c n n a . E d ito ria l O ffice: H ooni 706, M ills B u ild in g , W a sh in g to n , D . C.

T e le p h o n e : N a tio n a l 0848. C able: J ie c liem (W a n h in gton j

Published by the American Chemical Society, Publication Office, 20th &

N ortham pton Sts., E aston, Pcnna. Entered as second-class matter a t the Post Office at E aston, Penna., under the Act of March 3, 1879, as -4 tim es a year. Industrial E dition m onthly on the 1st; Analytical Edition monthly on the 15th. A cceptance for mailing at special rate of postage provided lor in Section 1103, A ct of October 3, 1917, authorized July 13, 1918.

Annual subscription rate, In d o s t i u a l Ed i t i o n and An a l y t i c a l Ed i t i o n

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American Union, S2.25; Canadian postage, $0.75. Single copies: Industrial E dition, $0.75; A nalytical Edition, S0.50. Special rates to members.

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cannot be accepted as the reason for honoring a claim . Charles L. Parsons, Business Manager, M ills Building, W ashington, D . C., U. S. A.

4 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 12, NO. 8

S E T T I N G T H E P A C E I N C H E M I C A L P U R I T Y S I N C E 1 8 8 2

T V 7 T Km u io xmJ

B a k e r ^ A d a m s o n

Divisio n of G E N E R A L C H E M I C A L C O M P A N Y , 4 0 Re ct o r St., N e w York C .T ? A r c x tfs

Bales Offices: Atlanta . Baltimore • Boston • Buffalo • Charlotte (N. C.) • Chicago • Cleveland • Denver • Ilouston Kansas City . Milwaukee • Minneapolis • Montezuma (Ga.) • Newark (N .J.) • New York • Philadelphia • Pittsburgh

Providence (It. I.) • St. Louis • Utica (N. Y.)

Pacific Coast Sales Offices: San Francisco • Los Angeles • Pacific Xorthicest Sales Offices: Wenatchee (Wash.) • Yakima (Wash.) In Canada: The Nichols Chemical Company, Limited • Montreal • Toronto ♦ Vancouver

SYMPHONY IN PRECISION

I n th ese years of accurate tools a n d s k i l l f u l w o r k m a n s h ip , a p r e c is e ly m ade product is a practical certainty. Per­

fe c tio n in t h e o n e f in is h e d jo b is n o t enough, how ever. Like a k eyn ote sound­

ing through our tim es runs the constant query “Can y ou m aintain close tolerances on d ie production lin e ? ”

N ot in one industry, hut in m any indus­

tries, is the answer an unqualified Y ES!

P recision on the production lin e is an accom plished fact.

In the m anufacture of aeroplanes today, the hundredth p lan e is as accurate as the laboratory m odel. In autom obiles, the

thousandth car is as p erfect as the first.

P recision instrum ents to m ake th ese prod­

ucts com e off the production lin e as w ell.

M odem chem ical m anufacturing m eth ­ ods are no excep tion to this rule. B & A R eagents, the precise m easuring instru­

m ents of the chem ist, are an im portant factor in today’s “S ym phony in Precision!' As the m icrom eters o f the chem ical lab o­

ratory, B & A R eagents arc uniform ly u n e r r in g . Q u a n tity p r o d u c t io n o f fin e chem icals is also m ade p ossib le by the ap p lication of the sam e quality p rinciples th a t g o v e r n th e p r o d u c t io n o f B &A Reagents.

ANALYTICAL EDITION 5

s o d iu m o x a l a t ê P r i m a r y S ta n d a r d

N a ,C ,0 , A N A L Y T I C A L R E A G E N T

POISON

« a n i o D T Ch e m ic a l *

PRECISION

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 • Chicago • Philadelphia • N ew York

. . . . i n t h e L A B O R A T O R Y

Accurately measuring laboratory apparatus is of little value in analytical procedure unless the chemicals employed are free from im purities giving rise to erroneous results. M allinckrodt Analytical Reagents—each scrupulously refined to m eet predeterm ined sta n d ­ ards of purity—are especially designed to facilitate analytical pre­

cision. Chemists can depend upon M allinckrodt A. R. Chemicals because they conform to A. C. S. specifications.

S en d for new catalogue o f analytical reagents and other chem ­ icals for laboratory use. I t contains descriptions o f chem i­

cals suitable for every ty p e o f analytical work . . . gravi­

metric, gasom etric, colorim etric or titrim etric.

6 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 12, NO. 8

There’s a reason for H O SKIN S particular construction.

O n e p ie c e m u ffle aro u n d w hich co ile d C h ro m e l units a r e e a s ily w r a p p e d in g ro o v e .

T w o h e a v y C h ro m e l co ils in p a r a lle l, d e s ig n e d f o r o n e v o lta g e o n ly , p ro ­ v id e most d u ra b le e le m e n t.

M a k e o n e r e n e w a l a n d b e do n e w ith I t . " A ch ain is no stro n g e r th a n its w e a k e s t lin k ."

A d e lic a t e ly b a la n c e d slid in g d o o r, s ta y s p u t in a n y positio n a n d thus c o n se rve s h e a t.

Insulatio n 4 1 / j* th ick a ll a ro u n d . Yo u c a n 't f r y e g g s on the to p o f this fu rn a c e . Eco n o m ical on p o w e r.

• H oskins Labo rato ry Fu rna ces are desig ned around no one feature but w ith a ll factors in proper b a la n ce to m ake them of most v a lu e to y o u . T hese benefits are: durable Chrom el elem ents . . . hard to w e a r out but e a s y to ren e w ; a relative ly cool fu rn ace c a se for comfort and eco n o m y; a fu rn ace that d e live rs the goods month in and month out to your com plete satisfactio n . B uy from yo u r d eale r’s stock . . . H oskins M anufacturing C o m p a n y f Detroit, M ich.

W e h a v e a h a n d y little g a d g e t , c a lle d a H e a tin g U n it C a lc u la to r , th a t te lls h ow to m a k e c o ile d C h ro m e l units o f 2 7 5 to 1 ,0 0 0 w a tts . G la d to g iv e y o u o ne.

H O S K I N S P R O D U C T S

O

This F D - 2 0 4 fu rn a c e w a s d e s ig n e d , M r . C h e m ist, w ith y o u r in te re sts in m in d .

©

E a s y to g e t a t to f i x . Loosen C h ro m el h e a tin g unit te rm in a ls, re m o v e 4 c o m e r sc re w s a n d fro n t h e a t lifts o f f .

This sho w s the F D - 2 0 4 a sse m b led . H e a tin g cha m b er, 7 3 / s ' x 51/4" x 7 4 ".

E L E C T R IC H E A T T R E A T IN G F U R N A C E S • • H E A T IN G E LE M E N T A L L O Y S • • T H E R M O C O U P L E A N D LEAD W IRE • • PYROMETERS • • W ELD IN G W IRE • • HEAT RESISTAN T C ASTIN G S • • ENAM ELING FIXTURES » • SPARK PLUG ELECTRODE W IRE • • SPECIA L A LLO YS OF N ICKEL • > PROTECTION TUBES

I

. ^TMi;

■ sag

An Encyclopedia of Chemicals and Drugs lor the Chemist, Pharmacist, Physician, Dentisi & Veterinarian.

Thousands o f chem ists, pharm acists and physicians h a v e been w aiting for this n e w b o o k . You can n o w obtain a co p y at the

S P E C I A L P R I C E O F $ 3 . 0 0

(Price in C a n a d a , $3.50)

The Fifth Edition of

THE MERCK

INDEX

( 1940 ⁾

Is Now Available

• 1,060 pages—nearly twice the num­

ber of the previous editions.

• Contains more than 5,900 descrip­

tions of individual substances.

• An im portant new feature is the sec­

tion, “ Chemical, Clinico-Chemical Reactions, Tests and Reagents by the A uthor’s N am e” which includes more than 4,500 numbered Tests, Reac­

tions and Reagents.

• In the section on “ Coal-Tar Colors for Use in Foods, Drugs and Cosmet­

ics,” 113 colors are described.

• The section on “ Indicators” covers 126 indicators, and the section on

“M inerals” embodies the description, formulas, and percentage composi­

tion of 187 minerals.

• Another new section contains formu­

las for the preparation of Culture Media, Fixatives, and Staining Solu­

tions, comprising a total of 212 for­

mulas and methods of preparation.

• Also Useful Tables, Antidotes for Poisons, and Literature References.

Printed in clear type on English finish paper, bound in black semi-flexible imi­

tation leather covers and stamped in gold.

What Trade and Professional Journals Say about The Merck Index

B r ie f e x ce r p ts fro m so m e o f th e cu r re n t p u b lic a tio n s w h ic h ca rried r e v ie w s o f T h e M e r c k I n d e x :

“ B y r e a s o n o f t h e w e a l t h o f i n f o r m a t i o n c o n t a i n e d , T h e M e r c k I n d e x w i l l b e c o m e a n i m p o r t a n t p a r t o f e v e r y p h a r m a c e u ­ t i c a l l i b r a r y . " — D r u g T ra d e N e w s.

*4 T h i s e n c y c l o p e d i a o f c h e m i c a l s a n d d r u g s r e p r e s e n t s t h e m o s t e x t e n s i v e c o m p i l a ­ t i o n o f t h i s a u t h o r i t a t i v e r e f e r e n c e w o r k t h a t h a s b e e n u n d e r t a k e n s i n c e t h e f i r s t e d i t i o n a p p e a r e d i n 18 8 9 / ’ —T h e A p o th e c a r y .

“ C o n s i d e r i n g t h e p r i c e o f t h e b o o k , i t s c o n t e n t s a n d i t s i m p o r t a n c e , n o p h y s i ­ c i a n s h o u l d b e w i t h o u t t h i s e x c e l l e n t w o r k .” — T h e N e w Y o rk P h y sic ia n .

**T h e f i f t h e d i t i o n s h o u l d n o w s u p p l a n t

t h e p r e v i o u s e d i t i o n w h i c h i s , o r s h o u l d h a v e b e e n , i n t h e r e f e r e n c e l i b r a r y o f e v e r y p r e s c r i p t i o n r o o m . E v e r y p h a r m a ­ c i s t w i l l f i n d e x t e n s i v e u s e f o r t h i s t h e ­ s a u r u s i n h i s p r o f e s s i o n a l w o r k ; s o p l a c e i t b e s i d e y o u r U .S .P ., N .F ., a n d D i s p e n ­ s a t o r y w h e r e i t w i l l b e a v a i l a b l e f o r i n ­ s t a n t r e f e r e n c e — D r u g g is ts C ircu lar.

“ T h e M e r c k I n d e x w i l l b e a v a l u a b l e a d d i ­ t i o n t o e v e r y p h a r m a c e u t i c a l l i b r a r y , f o r i t i s i n f a c t a c o n d e n s e d , c o m p r e h e n s i v e a n d r e l i a b l e e n c y c l o p e d i a o f c h e m i c a l s a n d d r u g s f o r t h e c h e m i s t , p h a r m a c i s t , p h y s i c i a n a n d t h o s e i n a l l i e d p r o f e s s i o n s .* '

— M id w e ste r n D r u g g is t.

MERCK & CO. Inc. . R AH W AY, N . J.

In C a n a d a : M E R C K & C O . L i d • M O N T R E A L & T O R O N T O

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8 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 12, NO. 8

VON

C Z O E R N IG -A L B E R

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

E L E C T R IC H EA T IN G

FOR T E M P E R A T U R E S UP T O 750°C

5678-A.

M IC R O C O M B U S T IO N F U R N A C E , E le c tric , von C zo ern ig -A lb er, A .H .T . Co. S p ecificatio n , for te m p e ra tu re s u p to 75 0 °C . F o r e le m e n ta ry q u a n tita tiv e o rg an ic m ic ro a n a ly sis, in c lu d in g d e te rm in a tio n s fo r'c a rb o n a n d h y d ro g e n , n itro g e n b y th e D u m a s m e th o d , h alo g en s a n d su lfu r b y th e c a ta ly tic p ro ­ c ed u re a n d m e ta ls o r re sid u e s b y th e m e th o d s of P re g l, A lb e r a n d C o o m b s, a n d M e y e r a n d H o e h n e .

T h e o u tsid e dim ensions of th e furnace b o d y are 8 inches long X ZlA inches deep X 2 J4 in ch es high, w ith ch a m b e r 8 inches long X 1M inches deep X Y i in ch high. T h e hinged fro n t is of tra n s ite a n d can be raised w ith u n p ro te c te d fingers b y S tain less steel w ire h andle.

Provides u n ifo rm and constant temperatures w ith in the ranges required fo r m a n y types o f m icro tests sim p ly by changing the position o f the tube in the furnace, b u t th e use of tra n sfo rm e r or rh e o s ta t is su g g ested for critic a l w ork o r w hen th e te m p e ra tu re m u s t be chan g ed g ra d u a lly w ith o u t d istu rb in g th e tu b e.

When operated without a resistance and with tube placed against the rear wall of chamber, temperature remains con­

stant at 700°C to 730°C under normal voltage conditions. By moving the furnace so th at tube is midway between the front and rear of the chamber, temperatures between 670° and 700°C are obtainable. The lowest uniform temperatures are directly back of the hinged front where they are constant from 580° to 600°C. Constant temperatures can be attained in approximately 30 minutes without the use of a resistance. Average life of the heating element, when used without resist­

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

5678-A . M icro Com bustion Furnace, E lectric, von Czoernig-Alber, A .H .T . Co. Specification, as above described, on adjustable

s ta n d w it h leveling screws and adjustm ent for centering and clam ping com bustion tubes. Furnace bod y can be m oved laterally, either to right or left, on tracks 15M inches long;

also m ovable forward or backward for approxim ately 2 inches.

W ith contin uously variable transformer, cord and plug, but w ith out pyrom eter. For 110 volts, 50 to 60 cycles, a.c.

o n ly ... 85.00 5679-A. D itto, b u t w ith out transformer or rheostat; for 110 volts, a.c. or d.c...75.00 5680. M icro Com bustion Furnace, Electric, von Czoernig-Alber, identical w ith 5678-A, w ith ou t adjustable stand or sliding platform b u t w ith nickel plated supporting arm, m ounted

on support w ith Coors porcelain base and alum inum rod b y m eans of nickel plated brass clam p holder. W ith trans­

former (n o t show n in illu stration), cord and plug, bu t w ith­

ou t pyrom eter. For 110 v olts, 50 to 60 cycles, a.c. only 48.50 5681. D itto, b u t w ith ou t transformer, rheostat, support or clam p

holder; for m ounting by m eans of a clam p holder to any suitab le laboratory support. W ith cord, plug and snap sw itch, for use on 110 vo lts, a.c. or d .c... 35.00 5685. P yrom eter, w ith base m etal therm o-couple sufficiently sm all

for use inside th e micro com bustion tu be when necessary to check tem perature conditions of filling m aterials. Con­

sistin g of a d.c. m illiam m eter range 0 to 1200°C in 20°

d ivision, w ith 12-inch Chrom el-Alum el therm o-couple and 36 inches of insulated lead w ires... 23.50

More detailed in fo rm a tio n se n t upon request.

ARTH UR H. T H O M A S C O M PA N Y

R E T A IL — 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 PP A R A TU S AND R EA G E N T S

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

C ab le A ddress, “ B a la n c e ,” P h ila d e lp h ia

INDUSTRIAL a n d ENGINEERING CHEMISTRY

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

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

Testing Mold-Resistant Properties o f Oil Paints

A L aboratory M ethod

A LEX M . PARTANSKY AND RO B ER T R . M CPHERSON

B io ch e m ica l R e sea rch L a b o ra to ry , Dow C h e m ic al C o m p an y , M id la n d , M ich.

O

N E of the first to draw the attention of the American public to the prevalence of mold growth on oil paints was Gardner (8), who as early as 1913 pointed out th a t “in dam p localities, especially along the sea cost, mildewing of painted exterior surfaces is common” . Since th a t time and especially during recent years the importance of controlling mold growth on painted surfaces has attracted the attention of technical men.

Fi g u r e 1. Mo l d Gr o w t h o n Wa l l n e a r Re f r i g e r a t i o n Pi p e s

The paint mildewing problem is particularly serious in industrial plants where, owing to the nature of the processes involved, high humidity and fairly warm temperatures are maintained. Here the mold growth not only gives an un­

sightly appearance to the rooms and injures the paint, but presents a serious danger in contaminating the product.

Figures 1 and 2 are unretouched photographs taken in two such plants in the middle west area. In both cases the walls were repainted 3 to 4 m onths previous to photographing.

I t is generally agreed th a t under favorable conditions, a luxuriant mold growth readily develops on slow-drying long- oil (low in pigment) paints made up with impure oils con­

taining mucilaginous and nitrogenous m atter, which on dry­

ing give a soft and hygroscopic film (3,8,9,12). On the other hand, mildew troubles have been considerably lessened though not entirely eliminated (6,7, 8,10,12) in paints of high

pigment content (particularly zinc oxide), made up with high-grade rapid-drying spar varnish, which dry to a hard smooth film.

After 2 years of extensive experimental work on mold- growth prevention, during which upward of 200 commercial paints of various types were tested, the writers have yet to see a paint th a t would not mold under the conditions of the procedure described below, unless a good preservative had been added.

In the study of paint preservatives and the mold-resistant properties of paints in general the method most widely used in this country is th a t of field exposure in the southeast coastal states, usually Florida.

The chief disadvantage of the field test for the preliminary evaluation and comparison of paint preservatives, besides its slowness, is the lack of uniformity in the natural weather conditions, not only throughout the year (tests can be started, therefore, only once a year during the rainy season) b u t be­

tween the same seasons of different years. I t is also difficult to compare data obtained in different localities, for there is no such thing as “standard weather” (13).

To minimize weather variability and to remove the pos­

sibility of misleading results, field tests to be conclusive re­

quire repetition for several seasons.

Fi g u r e 2 . Ex t e n s i v e Mo l d Gr o w t h o n Wa l l Near concrete ceiling, through which there is a slow seepage of m oisture

from floor above

444 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 12. NO. 8 A good laboratory method carried out under standardized

conditions has a great advantage over the field exposure method for all preliminary or routine testing. I t is not only independent of the season and can be started whenever desired, but since all conditions can be reproduced exactly for every test, results obtained a t different times are com­

parable to each other.

Besides the advantage of standardization of the procedure, a laboratory method for testing mold-resistant properties of paints can be made to include and to intensify the principal factors favoring molding of paints under the conditions of actual service—namely, heavy seeding with selected molds found to grow well on paints, high humidity, warmth, and darkness. As a result, the time required for testing is short­

ened from several months to a few weeks.

A search of the literature revealed only two laboratory methods, both of which were described in the early work of G ardner (5).

In the first method drops of treated paint were placed on top of Czapek’s agar seeded with mold in Petri dishes and the in­

hibition zone was observed around the paint spots after 10 days of incubation. The inhibition zone test, however, does not tell whether the mold would or would not grow on a particular paint but only indicates the presence or absence of water-soluble fungi­

cide capable of inhibiting mold growth on agar.

The second method consisted of hanging paint panels seeded with a water suspension of molds in a chamber maintained at 30° C. and 85 per cent relative humidity; however (5), these panels developed no mold growth in 4 months.

In trying to devise a rapid laboratory method for testing mold-resistant properties of paint the authors endeavored to elaborate on the technique of seeding w ith spores, a method tried by Gardner on paints,, and also commonly employed in testing other materials, such as canvas (11). However, con­

sistent results could not be obtained and the method was finally abandoned in favor of the present “grafting” proce­

dure. Some of the experience gained, however, is very instruc­

tive.

Fi g u r e 3 . Te s t Pa n e l

Showing mold growth prim arily following lin es of scratching. P a in t on right contains preservative.

For instance, (1) scratching or otherwise breaking the sur­

face of the dry paint film helps to sta rt the mold growth along the scratch (Figure 3); (2) mold growth started locally, as on a drop of agar placed on the paint surface, does not spread far from the point of infection; (3) addition of “nutrients” , such as m alt extract, to the paint itself prior to painting is of little assistance in subsequent molding, while soaking the paint panels in m alt extract solution helps to sta rt the mold growth,

b u t also frequently results in bacterial contamination which actually interferes w ith the mold grow th; (4) excessive mois­

tening of the paint surface is detrim ental to mold growth.

In the authors’ new laboratory method for testing mold re­

sistance of oil paints the seeding is done by placing the painted surface in contact with an actively growing mold mycelium.

When this “grafting” procedure is carried out with due care and exactly as outlined below, the seeding is successful in a t least 99 per cent of the cases.

The mold now used in paint testing work by the present method, No. 29, is a rapid-growing Aspergillus forming dark brown spores. I t was originally isolated 2 years ago from a molded paint and selected for the paint-testing work from a group of 35 molds because of its exceptionally abun­

dant and vigorous growth on oil paints and its high resistance to toxicants. This choice is also supported by the fact th a t most of the molds reported as growing on oil paints in nature belong primarily to either Aspergillus or Penicillium genera

a, 4).

S ta n d a r d P r o c e d u r e

Pa n e l s (Figure 4). Wooden disks 7.5 cm. (3 inches) in

diameter and 0.625 cm. (0.25 inch) thick, cut from clear western white pine sapwood with grain running parallel to the plane surface, are used in the test. These disks are convenient to handle and fit the standard size glassware. I t was necessary to standardize the material, since the substratum over which the paint is applied somewhat affects the readiness with which the paint molds.

The disks are sanded on all sides and the edges are slightly rounded off to prevent paint from pulling away from the edges.

Since the pitch content of the wood varies considerably, for the sake of uniformity, to eliminate the additional variables, and to prevent discoloration of white paints, the panels prior to paint­

ing are extracted with a high-solvency naphtha (the authors use Skelly Solvent of B. R. 100° to 140° C.).

Pa i n t Ap p l i c a t i o n. The paint manufacturer’s directions as to the priming, thinning, number of coats, drying time between coats, etc., are followed when given. In the absence of instruc­

tions two coats are applied according to good painting practice.

For painting the panels the authors use 0.78 cm. (0.31 inch) wide, 1.875-cm. (0.75-inch) bristle brushes made by the George E.

Watson Company. During painting care is taken to prevent mixing of paints by using a clean dry brush for each paint (the used brushes are washed in several changes of turpentine and then in acetone).

To afford a direct comparison between the original and the fungicide-treated paints, one surface of each disk is divided by a shallow groove made with some blunt instrument along the diame­

ter running parallel to the wood grain. One half (as well as the adjacent edge) is painted with the test paint, while the other is painted with the original untreated paint. When the latter is not available some comparable paint known not to contain pre­

servatives is used.

After the paints are thoroughly dry and at least 5 days have elapsed after application of the second coat, the panels are soaked overnight in distilled water (this softens the paint film in a manner similar to rain action), and are then ready for seeding. Some­

times it is advantageous, before soaking the panels in water, to dip the unpainted backs of the disks into molten paraffin to prevent warping and paint peeling.

Se e d i n g. After soaking, the test panels are wiped dry with a towel and are laid painted side down on a 36- to 42-hour old cul­

ture of mold 29, grown on malt agar in 10-cm. Petri dishes.

For growing seeding mold cultures the authors use agar con­

taining 25 grams of Difco malt extract, 2 grams of Difco yeast extract, ana 15 grams of agar per liter of water. After hardening, the agar is seeded by swabbing with a water suspension of the mold. Aseptic microbiological technique is carefully observed during preparation of the seeding cultures. The disks are pressed down gently but firmly to ensure a good contact between the paint and the mold mycelium.

The age of the seeding mold culture, or rather the stage of its development, is critical; for best results it should be used exactly at the time when the sporangia are developing but before they begin turning dark. About 42 hours at 25° C. are required for the mold to reach this stage.

The test panels remain on the seeding culture for 20 to 24 hours at 25° C., in which time the mold not covered by the disks becomes dark.

Mo l d i n g. After seeding, the paint surface is gently sprayed with water from an atomizer to wash off any agar particles or other extraneous m atter that might be present, and the disks are embedded (painted side up) in Petri dishes by means of paraffin.

Just enough paraffin is added to cover the bottom of the disk and to fix it in place, leaving a groove between the edge of the disk and the side of the dish. The necessary moisture for mold growth is provided initially by spraying the paint surface from an atom­

izer and by placing 5 cc. of water in the groove; the water in the groove is periodically replaced as it evaporates. The disks em­

bedded in Petri dishes are incubated in a chamber kept a t 25°

to 30° C. and 60 to 70 per cent relative humidity. Better mold growth is obtained when the test disks are periodically watered and incubated in an ordinary incubator, as described, than when they are incubated in a saturated atmosphere of 95 to 100 per cent humidity.

(both natural and artificial) can be tested a t any particular stage of the breakdown.

The grafting method of seeding has also been found ap­

plicable for testing the mold resistance of canvas, awnings, etc., and for seeding with molds other than the one recom­

mended for paint testing.

C o n c lu s io n s

A rapid, dependable, and convenient laboratory method for testing mold-resistant properties of oil paints which gives consistent, reproducible results has been developed.

By the use of “half and half” panels, the treated and the original paints receive an identical treatm ent in all respects

Fi g u r e 4 . Te s t Pa n e l s Se e d e d w i t h Mo l d 2 9 b y Gr a f t i n g Me t h o d

N o te receding of mold growth duo to diffusion of preservative from treated paint on right in to control pain t on left side of panel at left.

Re a d i n g a n d Re c o r d i n g Re s u l t s. By this procedure it usually takes not more than 3 weeks to obtain the maximum growth, although with exceptionally hard paints a longer time may be required. However, it was found convenient, for the sake of comparison, and since both the rate and the maximum extent of growth are important, always to make readings 7 and 21 days after seeding.

For recording mold growth a binomial system with ten as the maximum value for each reading is used. In this system the first number of the pair indicates the “extent of growth” and the second the “intensity of growth” . By the extent is meant the fraction of the surface that is covered with mold. To illustrate the interpretation of these readings: “4-10” means “an abun­

dant growth over about 40 per cent of the surface” , while “ 10-1”

means “a scanty growth over the entire surface”.

D is c u s s io n

The method described above has been used with excellent results in the authors’ laboratory for over 18 months. As a general rule a very good agreement is obtained between the duplicate plates. Any discrepancies in the results are usually due to the fact th a t the preservative is present in the so- called borderline concentration, a t which minor differences in conditions determine whether or not the growth takes place.

Another very im portant feature of this laboratory method is th a t it allows separation of the two factors involved in the molding of the paint panels during field testing— (1) the original effectiveness of the preservative treatm ent and (2) the effect of weathering and breakdown of the paint film (including the loss of the toxicant). In other words, by this method the mold-resistant properties of the original paint as well as of the paint films subjected to weathering

throughout the entire procedure, thus permitting a direct comparison between them.

L ite r a tu r e C ite d (1) d’Ans, Z. angew. Chem, 41, 1193 (192S).

(2) Gardner, H. A., J . Franklin Inst., 175, 59 (1913).

(3) Ibid., 177, 533 (1914).

(4) Ibid., 179, 681 (1915).

(5) Gardner, H. A., Hart, L. P., and Sward, G. G., Am. Paint and Varnish Mfg. Assoc., Set. Ct'rc. 442, 242 (1933).

(6) Harry, R. G., Paint Manuf., 6, 309 (1936).

(7) Hart, L. P., Paint Varnish Production Mar., 13, 12 (Aug., 1935).

(8) Hofmann, W. F., A m . Paint J ., 22, 22, 24, 58, 60 (Fob. 7, 1938).

(9) Kempf and Peters, Farben-Ztg., 39, 1019 (1934).

(10) McLachlan and Floren, J., J . Oil Colour Chem. Assoc., 22, 180 (1939).

(11) Thom, C., Humfeld, H., and Holman, H. P., Am . Dyestuff Reptr., 23, 581-6 (1934).

(12) Weise, Kurt, Farben-Ztg., 39, 412, 444 (1934).

(13) Werthan, S., and Ashman, G. W., Official Digest Federation Paint & Varnish Production Clubs, No. 176, 235 (May, 1938).

Co r r e c t i o n. In the article entitled “Analysis of Cationic Surface-Active Agents of Trivalent Nitrogen Type” [ In d. En g. Ch e m., Anal. Ed., 1 2 , 402 (1940)] there are two minor errors.

In the paragraph beginning “Hopper, MacGregor, and Wilson,”

the fifth sentence should read “Sulfuric acid because of its low volatility” In Table III the average of sample A should be given as 79.9 per cent.

Ra l p h Ha r t

Critical Solution Temperatures and A niline Points o f Some Butane Hydrocarbons

CLIFFORD G. LUDEMAN, T h e Texas Com pany, P o rt A rth u r, Texas

A

N U M B ER of correlations of physical properties of hydro­

carbons or hydrocarbon mixtures are based upon aniline points. In order to extend the usefulness of these correla­

tions, aniline point d ata for various butane hydrocarbons are needed. Since necessary data were lacking in the literature, the current study was undertaken to determine the aniline points of some of the butane hydrocarbons.

Chavanne and Simon (2) introduced the use of the critical solu­

tion temperature, the maximum miscibility temperature of hydro- carbon-aniline mixtures for the study and analysis of hydrocar­

bons or hydrocarbon mixtures. A modification was advanced by Tizard and Marshall (IS) termed the aniline point, which is the miscibility temperature of equal volumes of hydrocarbon and ani­

line. Evans (6) pointed out that the differences between the critical solution temperatures and aniline points are usually small and that the two terms have been used indiscriminately. Or- mandy and Craven (10) demonstrated the adverse effect of water, 1 per cent of water in the aniline causing a 5.9° C. rise in the ani­

line point of n-heptane. Because of its ease of purification and wide use, Brame and Hunter (1) recommended n-heptane (from Pinus sabiniana) as a standard when used with an aniline whose water content was sufficiently low to yield an aniline point of 70.0° C.

Critical solution tem peratures and aniline points for various hydrocarbons as found in the literature, as well as the values derived from this study, are presented in Table I and shown graphically in Figure 1. Disregarding the butane hydrocar­

bon values shown, the d ata indicate minimum values in the several series which require experimental values for lower hydrocarbons for an accurate extension of the various curves.

The values derived in this study clearly dem onstrate these minima.

Because of the low boiling points of the butanes, none of the existent methods as described was applicable for this work.

An apparatus adaptable to work with butanes has several im­

NUMBER OF CARBON ATOMS PER MOLECULE OF HYDROCARBON

portant limitations—it m ust withstand high pressures, since, for example, isobutane has a vapor pressure on the order of 250,000 kg. per sq. meter (350 pounds per square inch) a t 110° C., it m ust be light enough to permit weighing on an analytical balance, and, finally, it m ust be of a form permit­

ting manipulation in a bath of liquid nitrogen used in the fill­

ing of the apparatus. The apparatus developed is described below. No claim for novelty is made, since the procedure used resembles in some details other known methods. Shep­

ard, Henne, and Midgley (11) used sealed tubes b u t reported insufficient details to allow duplication. Levin (7) has sug­

gested the use of a 10-cm. length of 7-mm. glass tubing sealed a t one end and closed by a small cork and sealing wax a t the other end. Wilkinson (14) used a semimicroapparatus which was not described.

T a b l e I. A n i l i n e P o i n t s a n d C r i t i c a l S o l u t i o n T e m p e r a -

Reference

This work (I I) ( 1 1 ) T his work

a nhi)

(u)(11)

(1 2) (1 2) (1 2) (12) T h is work

(3)

( S )

U)(3) (3)

(s)

T his work TURES

Critical

Aniline Solution

Hydrocarbon P oin t

° C .

Reference Tem perature

° C .

n-B u tane 8 3 .1 T h is work 8 4 .1

n-Pcntan e 7 0 .7 (5) 7 1 .4

7 1-H exane 6 8 .6 .W 6 9 .0

n -H eptane 7 0 .6 T h is work 7 0 .8

?i-Octane 7 1 .7 (5) 7 1 .8

n-N on ane 7 4 .5 ¥) 7 4 .4

n-D ecane 7 7 .5 (6) 7 7 .5

n-Undecane 8 0 .6 (5) 8 0 .6

n-D odecane 8 3 .7 (*) ^{8 3 .7}

n-Tridecane 8 7 .0

n -Tetradecane 8 9 .5

n-Pentadecane 9 2 .0

n-H exadecane 8 8 .0 \ej 9 5 .0

Isobutane 1 0 7 .6 T h is work 1 0 9 .0

Isopentane 7 7 .8

2-M eth ylp en tan e

2-M ethylh exan e 72 *.8 (¿) ^{7 4 .7}7 4 .1

2-M eth ylh ep tan e 7 4 .0

2-M ethyloctan e 7 7 .5

2-M ethyln onane 8 0 .3

Isobu tene 1 4 .9 T his work 1 5 .8

2-M ethylb utene-2 11.0 a)

2-M ethylp en tene-2 2 4 . 0a (6)

“ Isohcxene mixture.

Fi g u r e 1. C r i t i c a l S o l u t i o n T e m p e r a t u r e s vs. M o l e c u l a r S i z e o f H y d r o c a r b o n s

A p p a r a tu s

The containers used for the determinations of the miscibility temperatures are best described by reference to Figure 2. The tubes were blown from Pyrex tubing 3 mm. in inside diameter and 5 mm. in outside diameter, and had a chamber 4 cm. in length with a capillary at one end and a handle at the opposite end at­

tached to the sealed-off portion. The end with the capillary ended in a length of tubing sufficient to permit handling during the sealing-off operation and to permit temporary closure with a small cork. A slip of paper in the closed handle contained an identification number.

M a te r ia ls

A n i l i n e . Five hundred cubic centimeters of aniline (J. T.

Baker’s c. p. analyzed grade) were slowly distilled in a dry appa­

ratus and the central 100-cc. portion boiling at 184.4° C. (cor­

rected) was collected. This fraction was immediately sealed in ampoules in 10-cc. portions and stored until used.

n -H E P T A N E . One liter of n-heptane (California Chemical Company’s c. p. grade) was slowly distilled with the use of a high- temperature fractionation column of the Podbielniak type and the middle 100-cc. portion boiling at 98.4° C. (corrected) was col­

lected.

n -B tjT A N E . The c. p. grade of n-butane as supplied by the Phillips Petroleum Corporation was found to be above 99.9 per 446

ANALYTICAL EDITION 447 on a small adjustable elcctric hot plate and equipped with an efficient stirrer and a totally immersed thermometer. The ther­

mometers used were of the Anschutz type graduated to 0.2° C.

but could be read to 0.1° and had been tested by the National Bureau of Standards. Heating and cooling (by means of chipped ice with isobutene whose irascibility temperature was below that of the room) were effected at about 0.2° C. per minute within the range of 1° of the value as ascertained by an initial trial. Read­

ings were taken with both ascending and descending temperatures which agree within 0.1° C. Only values obtained with descend­

ing temperatures were recorded, check values being obtained.

The sudden appearance of a milky cloud in the clear mixture was taken as the criterion for reading the miscibility temperature with descending bath temperatures. The temperatures observed are thought to be accurate, owing to efficient stirring, slow rates of temperature change, and approximately similar rates of lag of the thermometer and of the miscibility tube, since both were of the same order of size.

cent purity by a low-temperature fractional distillation with a column of the Podbielniak type. The material contained no un­

saturated components, as shown by zero absorption in 87 per cent sulfuric acid and by zero contraction on catalytic hydrogenation according to the method of McMillan, Cole, and Ritchie (9).

I s o b u t a n e . Isobutane (Matheson's “pure commercial”

grade) was passed through four wash bottles filled with 95 per cent sulfuric acid, through an Ascarite-filled tower, through 40 per cent potassium hydroxide, and finally through a tower filled with anhydrous calcium chloride, after which it was condensed in a steel bomb cooled with a dry-ice and kerosene bath. Analysis of the product by low-temperature fractional distillation showed over 99,9 per cent purity, with zero absorption in 87 per cent sul­

furic acid and zero contraction on hydrogenation demonstrating the absence of unsaturated components.

I s o b u t e n e . ierf-Butyl alcohol (Eastman Kodak Company's purest grade) was dehydrated with oxalic acid to yield isobutene which was dried by passage through a tower filled with anhydrous calcium chloride, after which it was condensed in a steel bomb cooled by a dry-ice-kerosene bath. The isobutene was redistilled from the bomb through 30 per cent potassium hydroxide, dried by passage through a tower filled with anhydrous calcium chlo­

ride, and recondensed in a steel bomb cooled in a dry-ice-kerosene bath. The yield of purified product was 88 per cent of the theoretical based on the ierZ-butyl alcohol. The isobutene was over 99.9 per cent pure by a low-temperature fractional distilla­

tion, 100.0 per cent unsaturated according to hydrogenation, and 100.0 per cent isobutene by reaction with anhydrous hydrogen chloride according to the method of McMillan (8).

P r o c e d u r e

Precautions were taken to have and to maintain dry materials, equipment, and conditions at all times. The miscibility tubes were always tightly stoppered except while pipetting or weighing and until sealed off. All weighings were made to 0.1 mg. on an analytical balance equipped with a special stirrup of chromel wire used to hold the tubes. All pipetting was performed as rapidly as possible.

By means of a capillary-tipped pipet, aniline was introduced into a weighed miscibility tube, then the capillary and upper part of the tube were heated in a narrow flame to volatilize adhering droplets of aniline, the resultant vapor was sucked out quickly by vacuum, and the tube was cooled and reweighed. The miscibility tube containing the weighed aniline was immersed in liquid nitrogen to the bottom of the capillary constriction. The lique­

fied hydrocarbon was then cooled to partial crystallization (except

«-heptane) to ensure freedom from dissolved water, and the hydrocarbon was introduced into the miscibility tube on top of the aniline by means of a capillary-tipped pipet. The capillary of the miscibility tube was sealed off by means of a hand gas-oxygen blast torch, care being taken to obtain smooth seals and to avoid the loss of glass. The sealed tube was removed from the liquid nitrogen bath, warmed to room temperature, and again reweighed together with the glass tip which had been removed during the sealing operation. The volume ratio of hydrocarbon to aniline was determined by the following equation:

T a b l e II. M i s c i b i l i t y D a t a

Ratio = weight of hydrocarbon X 1.0252

weight of aniline X density of hydrocarbon at 60° F.

where 1.0252 is the density of aniline at 60° F. based on water at 4° C., this Fahrenheit temperature being used since it is the gen­

eral standard in the petroleum industry.

The prepared miscibility tube was introduced and shaken in a bath consisting of a 2-liter jar filled with water or glycerol, heated

Sample Hydrocarbon Num ber

n-H eptane d G0° F ./ 4 0

0 .6 8 7 8 C.

u-Butane 9

d 60° F ./4 ° C. 10 0 .5 8 4 3 11

12 13 14 15 16 17 18

Isobutanc 19

d 60° F ./4 ° C. 20 0 .5 6 4 6 21

22 2324 25 26 27 28

Isobutene 29

d 60° F ./4 ° C. 30 0 .6 0 3 0 31

32 33 34 35 36 37 38

W eight of W eight M iscib ility

Hydro­ of Volum e Tem pera­

carbon A niline0 R atio ture

Gram Gram ° C.

0 .0 4 1 5 0.1 1 2 1 0 .5 5 2 6 7 .5

0 .0 4 9 5 0 .1 2 3 8 0 .5 9 7 6 7 .8 0 .0 5 4 2 0 .0 9 1 5 0 .8 8 3 7 0 .0

0 .0 6 1 5 0 .0 9 1 7 1 .0 0 7 0 .7

0 .0 6 5 2 0.0 8 9 1 1 .0 9 7 0 .7

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

0 .0 7 6 9 0 .0 8 8 8 1.2 9 7 0 .3

0 .0 7 9 6 0 .0 7 7 2 1 .5 4 6 9 .7

0 .0 4 9 9 0 .1 4 9 2 0 .5 8 7 7 5 .5 0 .0 4 7 3 0 .1 2 7 7 0 .6 5 0 7 7 .7 0 .0 4 8 5 0 .1 0 7 6 0 .7 9 1 8 0 .4 0 .0 5 9 3 0 .1 1 2 8 0 .9 2 3 8 2 .4 0 .0 5 3 8 0 .1 0 0 8 0 .9 3 7 • 8 2 .8

0 .0 6 7 4 0 .1 0 5 9 1 .1 2 8 3 .8

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

0 .0 9 1 7 0 .1 3 4 5 1 .2 0 8 3 .8

0 .0 7 2 9 0 .0 9 7 6 1.31 8 4 .1

0 .0 9 5 4 0 .0 9 3 3 1 .7 9 8 3 . G

0 .0 3 9 8 0 .1 1 5 7 0 .6 2 4 9 2 .7 0 .0 4 5 2 0 .1 1 6 2 0 .7 0 7 9 8 .3 0 .0 5 2 8 0 .1 1 3 7 0 .8 4 3 1 0 3 .6 0 .0 5 5 4 0 .0 9 9 9 1 .0 1 1 0 7 .8 0 .0 5 6 3 0 .0 9 4 6 1 .0 8 1 0 8 .6 0 .0 6 4 4 0 .1 0 6 1 1 .1 0 1 0 8 .8 0 .0 7 9 5 0 .1 2 2 5 1 .1 8 1 0 9 .0 0 .0 7 4 0 0 .1 0 3 4 1 .3 0 1 0 8 .8

0 .0 6 6 9 0 .0 9 2 5 1 .31 10 8 .9

0 .1 1 4 7 0 .1 0 1 7 2 .0 4 1 0 2 .9 0 .0 5 2 9 0 .1 2 0 3 0 .7 4 8 1 1 .8

0.0 4 8 9 0.1 0 1 1 0 .8 2 2 1 3 .2

0.0 5 3 1 0 .0 9 8 6 0 .9 1 5 1 4 .2

0 .0 7 2 5 0.1 1 7 1 1 .0 5 1 4 .9

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

0 .0 7 4 0 0.1 0 7 1 1 .1 7 1 5 .5

0 .0 6 9 2 0 .0 9 7 8 1 .2 0 15 .4

0 .0 6 9 3 0 .0 9 3 3 1 .2 6 1 5 .6

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

0 .1 0 0 9 0 .0 8 9 2 1 .9 2 1 5 .5

« A niline, d 60° F ./4 ° C., 1 .0 2 5 2 .

D is c u s s io n

The miscibility data developed are tabulated in Table II.

The derived critical solution temperatures and aniline points recorded in Table I were obtained by graphing miscibility temperatures vs. the volume ratios of hydrocarbon to aniline.

n-Heptane was used with this procedure for comparison with other results, an aniline point of 70.6° C. and a critical solu­

tion tem perature of 70.8° C. being obtained. The literature records values for the aniline point and critical solution tem ­ peratures of n-heptane varying from 68° C. (10) to 71° C. (6).

The effect of water in raising the miscibility tem perature has already been mentioned, b u t it is not believed th a t this ex­

planation is applicable to these results in view of the precau­

tions taken in this study. The values for the three butane hydrocarbons appear to be generally consistent with the other data as shown by Figure 1.

S u m m a r y

A method for the determination of the miscibility tempera­

tures for mixtures of volatile hydrocarbons and aniline is pre­

sented. The aniline points of n-butane, isobutane, and iso-