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

A n a l y t i c a l

E d i t i o n

Vo l.

5, No. 5

Se p t e m b e r

15, 1933

I n d u s t r i a l

A ND E N G I N E E R I N G

C h e m i s t r y

VOL. 25, CONSECUTIVE NO. 31

Pu b l i s h e d b y t h e Am e r i c a n Ch e m i c a l So c i e t y Ha r r i s o n E . Ho w e, Ed i t o r

Pu b l ic a t i o n Of f i c e: E a s to n , P a .

Ed it o r ia lO r n c i :

R o o m 706, M ills B u ild in g , W a sh in g to n , D . C , Te l e p h o n e: N a tio n a l 0848 Ca b l k: J ie c h e m (W a s h in g to n )

Ad v e r t i s in g De p a r t m e n t: 332 W e st 4 2 n d S t.,

N ew Y o rk , N . Y . Te l e p h o n e: B r y a n t 9-4430

C O N T E N T S

18,200 Copies of This Issue Printed Photom etric Investigation of Nessler Reaction and W itting

M ethod for D eterm ination of Ammonia in Sea W ater . . ... Henry E. Wirth and Rex J . Robinson 293 X -R ay M ethod for Q uantitative Comparison of Crystallite

Orientation in Cellulose F i b e r s ...

... Wayne A . Sisson and George L. Clark 296 Colorimetric D eterm ination of Fluorine . W. D. Armstrong 300 D eterm ination of Pyridine Bases in the'Presence of Ammo­

nia ... F. II. Rhodes and K . R. Younger 302 D eterm ination of T itanium in Plain-Carbon, High-Chro-

mium, and 18 Chromium -8 Nickel S te e l s ...

...Thos. R. Cunningham 305 A Modified S o x h l e t ...

...Thomas R. Liston and William M . Dehn 306 Standardization of K auri B utanol T est for P ain t and Lac­

quer T hinners ...

. . . . L .C . Beard, V. L. Shipp, and IK. E. Spelshouse 307 Effect of C ertain Preservatives on the Determination of

Sucrose by th e Invertase M e t h o d ...

. . . Charles F. Poe, M ary Cooley, and TV. F. W ill 309 Q uantitative Spectrographic Studies of Co-precipitation.

I I ...Louis Waldbauer and E . St. Clair Gantz 311 D eterm ination of Calcium in Lcad-Calcium Alloys of Low

Calcium C ontent. Beverly L. Clarke and Leland A . Wooten 313 Silicon Tetrafluoridc Volatilization . . W , D. Armstrong 315 Adsorption of Alcohol by Fibrous M aterials . R . T . Mease 317 Asbestos in Perm anganate T itr a ti o n s ...

... R, W . Curtis and J , Finkelslein 318 E stim ation of T otal and Bound (D) Gossypol in Cottonseed

M e a l ...F. II. Smith and J . 0 . Halverson 319 Relation of M oisture to E xtraction of Gossypol from Cot­

tonseed M eal w ith E t h e r ...

... ... J . 0 . Halverson and F. H. Smith 320 Preparation of Perm eable E xtraction Thimbles for Labora­

tory F i l t r a t i o n ...F. J . Williams 322 Calibration and S alt E rror of the Antim ony Electrode . ■

...Norman J. King 323 A M ultiple Steam B a th ...

...Warren L. Beuschlein and William M . Dehn 327 T yndallm etric Exam ination of Filtered Liquors . . . . .

... A . B. Cummins and M . S . Badollet 328

Determination of o-Nitrotoluene in Nitrocellulose Powder by the Immersion R e f r a c to m e te r ...

... John A . O’Callaghan and Stanley G. Cook Determ ination of Zirconium in Plain Carbon and Alloy S t e e l s ... Thos. R. Cunningham and R. J . Price Microburet for Potentiom etric M icro an aly sis...

...II. L. Lochte and Anna Hoover W ater of Crystallization in T otal Solids of W ater Analysis . ...V. P.SokolojJ Variable-Control Stillhead for Laboratory Columns. . . .

... S . C. Rothmann Method for D eterm ining the Dustiness of Coal and Coke .

...A . R. Powell and C. C. Russell A Study of Bunsen’s M e t h o d ...

...K. Braddock-Rogers and K . A . Krieger Automatic Pressure Regulators for Vacuum Distillation.

I I ... E .B . Hershberg and E . I I . Huntress A Continuous Air-Lift E xtractor...

... Ray P. Chapman and Louis P . Hammett Use of Glycerol in Io d o m e try ...

...A . T. Bawden and S . K . Dyche Microbomb for D eterm ination of Organic H alogens. . . ,

...Fred E . Beamish Ground-Glass J u n c t io n s ... Harlan L. Baumbaeh New M achine for Laboratory E valuation of Fatigue of

Rubber Compounds Flexed under Compression . . . . ... Leslie V. Cooper A Circulator for Ice W a t e r ...L . L. English A Mechanically O perated B uret . . Carrell II. Whilnah Use of Pum p as Gas S a m p l e r ... Robert C. Lee Determ ination of E thyl Alcohol in Gasoline-Alcohol Mix­

tures Using a Zeiss Immersion R efractom eter...

...F .S . Mortimer and Elmer H . Giese A Simple Autom atic W ater Still . . . . II. B . Gordon An Adjustable Tem perature Regulator . W. George Parks M icroabsorption S p e c t r a ...

...Charles R. Naeser and B. S . H opkins An Air T rap for W ater L i n e s ...

...Leo Lehrman and E k in A . Kabat 333 334 335 336 338 340 342 344 346 347 348 349

330 351 352 354

356 357 357 358 358

S u b s c r ip tio n to i o n m e m b m , I r o n m u A i i a x e E s o i s r a S n r e C b m j s t b t , *7.50 p e r y e a r. F o re ig n p o s ta g e *2.00, e x c e p t to c o u n trie s a c c e p tin g m a il a t A m e ric a n d o m e s tic r a t e , a n d to C a n a d a , 7 5 c e n ts . A n a l y t i c a l F . d i t i o k < 9 , «*»«»•. F o reign p o s ta g e , 50 c e n ts ; C a n a d a , 25 ce n ts . N k w b E d i t i o n o n ly , $1-50. p e r yea^\

a d d re s s , a n d claim s f n o claim s w ill b e i "

b e allo w ed fo r is su e s lo s t a s a r e s u lt 01 msuuiuieiit* uw w w v u « -» » --- — ^ - .__... *

a c c e p te d a s th e re a s o n fo r h o n o rin g a claim . If ch a n g e of a d d re s s im p lies a ch a n g e o f p o s itio n , p le ase in d ic a te its n a tu r e .

F o re ig n p o s ta g e , 50 c e n ts ; C a n a d a , 25 c e n ts . S u b sc rip tio n s, c h a n g e s of

T he Am e r i c a n Ch e m i c a l So c i e t y a l s o p u b l i s h e s the Journal of the American. Chemical Societr a n d Chemical Abstractt.

When analysis controls profit

CENCO-DeKHOTINSKY

L a b o r a t o r y D ^{ryin g} O ^{v en s}

ARE SPECIFIED

T im e and again you w ill find the ex clu siv e u se o f Cenco oven s associated w ith the p rod u ction or p rocessing o f products w hose daily analysis actually controls purchase p rices or sellin g p rices— products w hose analyses are w ritten in to contracts.

It m eans, sim p ly, that carefu l com p arison o f p erform ances reveals the sup erior con trol and d is­

tribution o f tem perature for w h ich Cenco oven s are design ed and built.

A Few M a n u fa c tu re r s W ho Use Cenco O vens in T h e ir L a b o r a to r ie s —

G e n e r a l E le c tr ic Co.

IV e stin g h o u se E le c tr ic &

M fg . Co.

I V e stin g h o u se L a m p C o.

W e s te r n E le c tr ic Co.

L e v e r B r o th e r s

C a m p b e ll S o u p C o m p a n y B . F . G o o d r ic h C o m p a n y D u P o n t R a y o n C o m p a n y G o o d y e a r T ir e & R u b b e r

C o.

F o rd M o to r C o m p a n y A r m o u r a n d C o m p a n y D e vo e a tu l R e y n o ld s C o.,

I n c .

K r a f t - P h o e n i x C h e e s e C o rp .

S t a n d a r d O i l C o . o f I n d ia n a

C u d a h y P a c k in g C o m p a n y M o n t g o m e r y W a r d &

C o m p a n y

J o h n s -M a n v ille C o r p o r a ­ t io n

R e p u b lic R u b b e r C o m ­ p a n y

C h a m p io n S p a r k P lu g C o.

B u c k e y e C o tto n O il C o.

B e ll T e le p h o n e L a b o r a ­ to r ie s

R .C .A . V ic to r C o ., I n c . E a s tm a n K o d a k C o.

P r o c te r & G a m b le C o.

B a k e lite C o r p o r a tio n C a r b id e & C a r b o n C h e m ­

ic a ls C o rp .

E . I . D u P o n t d e I \e m o u r s

& C o.

C o rn P r o d u c ts R e fin in g C o.

C h r y s le r C o r p o r a tio n G r a s s e lli C h e m ic a l C o.

T ex a s G u lf S u lp h u r C o.

D e lc o - R e m y C o r p o r a tio n N a tio n a l C a r b o n C o m ­

p a n y

K i m b e r l y C la r k C o r p o r a ­ tio n

G e n e r a l E le c tr ic X - R a y C o rp .

U n iv e rsa l O il P r o d u c ts C o.

B u c y r u s -E r ie C o m p a n y H u d s o n M o to r C ar C o m ­

p a n y

P a c k a r d E le c tr ic C o m p a n y

C e n c o -D e K lio tin sk y T rip le W all O vens

N o. 9830B N o. 9830C

S h e lf A rea, 282 S q. in . S h e lf A rea, 476 S q . in .

$140.00 $220.00

M a d e f o r E ith e r 110 o r 220 V o lts

W x DO 001 NAT

A s k F or D e s c r ip tiv e F o ld e r o f Cenco O vens, No. 7F

©OMHMhr

L a b o r a t o r y rajfff S u p p l i e - s

^A pparatus C hem icals

N e w Y o r k - B o s t o n - C H I C A G O - T o r o n t o - L o s A n g e le s

P u b lis h e d b y th e A m e ric a n C h e m ic a l S o c ie ty , P u b lic a tio n Office, 2 0 th & N o r th a m p to n S ts ., E a s to n , Pa.

E n te r e d a s seco n d -class m a tte r a t th e P o s t Office a t E a s to n P a ., u n d e r th e a c t o f M a rc h 3, 1879. a s 4 2 tim e s a y e a r. I n d u s tr ia l E d itio n m o n th ly on th e 1 s t; N ew s E d itio n o n th e 1 0 th a n d 2 0 th ; A n a ly tic a l E d itio n b im o n th ly o n th e 1 5 th . A c c e p ta n c e fo r m a ilin g a t sp ecial

r a t e o f p o s ta g e p ro v id e d fo r in S e c tio n 1103, A c t o f O c to b e r 3 , 1917, a u th o r iz e d .J u ly 13, 191S.

September 15, 1933

...

To Give Your Tires More Mileage

Electric

FURNACES

Electrical Heat Possible^The

ments are easy to renew, and of such durability th at when they at last wear out, it serves to remind the chemist of their long life. Literally thousands of Hoskins furnaces are in use, some of them 20 years old, and still going. Catalog 53Y con­

tains information that might be helpful to you. Hoskins Mfg. Co., Detroit, Mich.

HOSKINS

T H IS furnace is used by the Firestone Tire and Rubber Co. of California, to keep tab on the composition of their tire ingredients, to give Fire­

stone users more and more tire mileage. This is a typical use

of Hoskins furnace—helping

to uphold and improve quality

of product. The furnaces also

help the chemist by. giving him

virtually no concern and being

always on the job, when

needed. Their Chromel ele-

A N A L Y T I C A L E D I T I O N Vol. 5, No. 5

RETESTED

K

RETESTED

K

< E X A X >

U5A

T D

K

IMBLE Blue Line Exax Pipettes are made from extra heavy tubing of very uniform bore, automatic-machine- made, carefully selected to eliminate pieces with blisters, stones or streaks.

IM P O R T A N T FEATURES:

1. Designed to deliver contents accurately and at a proper speed.

2. Delivery ends are tapered grad u ally; tips are ground and slightly bevelled.

3. The tops are smoothly finished.

4. Volumetric and other pipettes have joints that are carefully made without constrictions.

5. Expertly calibrated at 2 0 °C to deliver ca ­ pacity by free outflow through tip. No drain age period allowed. W here the small amount rem aining in the tip is to be added this is indicated by a frosted band at the top.

6. A ll calibration lines are deeply acid-etched and filled with a durable blue fused-in glass enamel.

7. An entirely new type of calibration lining for accurate and rapid reading. Short lines for intermediate divisions with encircling lines at the main graduation points.

8. Retested and retempered (strain-free).

V O L U M E T R IC A N D O ST W A LD P IP E T T E S

Size Tolerance Size Tolerance

1 ml. ± 0 .0 1 2 ml. _{1 5} ml. ± 0 .0 6 ml.

2 ml. .012 ml. ₂₀ ml. .06 ml.

3 ml. _.02 ml. ₂₅ ml. .06 ml.

4 ml. .02 ml. ₅₀ ml. .1 0 ml.

5 ml. .02 ml. 100 ml. .1 6 ml.

10 ml. .04 ml. 200 ml. .20 ml.

M E A S U R IN G A N D S E R O L O G IC A L PIPETTES

1/10 ml. ± 0.005 ml.

2/10 ml. .008 ml.

1 ml. _.02 ml.

2 ml. .02 ml.

5 ml. _.04 ml.

10 ml. .06 ml.

25 ml. .10 ml.

KIMBLE

STOCKED BY LEAD ING LABORATORY SUPPLY HOUSES THROUGHOUT THE UNITED STATES A N D C A N A D A

GLASS C O M P A N Y

V I N E L A N D , N E W J E R S E Y .

N E W Y O R K . P H ILA D ELPH IA • B O ST O N • C H IC A G O • DETROIT

Septem ber 15, 1933 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

o Y ^ S ^ 0 0 0 ^ 0 . \ ^ e

A c ° ° a * '®

O "

o ' ^ QrCV x\o O ^ - sv t t ^ e 0 \ \ c * e1 s 9 e C

^ 9 \ * '• '* oW

0^ ei

p V ° ^ V c x V e ^ '

^ ■ " Z V * ° ^ ^

K « ” * (V (

c \ e O ' V v e ° A t ° ' - v , o A ^ 5 C - v - v

C O ^ »

s s s f

1^° sm«!

8

WHEN ORDERING C.P.’s

A Section of the Control Laboratories which guarantee the high quality of Merck’s C. P.'s.

T

HE U nited States P h arm aco p o eia p ro tects the P h a r­

m acist, the P hysician an d th e P ublic, fo r a chem ical can n o t lawfully be labeled “ U .S.P.” unless it strictly conform s to th e stan d ard s o f th a t official b o o k .

T h en th ere are the “ R ecom m ended Specifications fo r A nalyti­

cal R eagent C hem icals” o f the C om m ittee o n G uaranteed R eagents, A m erican C hem ical Society.

W hat o f the chem icals you receive, how ever, w hen you o rd e r

“ C .P .” and do n o t specify M erck? T h e re are n o uniform official stan d ard s fo r C.P. chem icals c o rre sp o n d in g to those p rescrib ed fo r U .S.P. p rep aratio n s o r th o se recom m ended fo r reag en ts. Each m anufacturer has h is o w n stan d ard s, his o w n m ethods o f testing, and his o w n in te rp re ta tio n o f tests.

Even th o u g h chem icals from tw o o r m o re m anufacturers may show the sam e purity o n th e ir labels, th e actual im ­ purity co n ten t may vary w idely due to different m ethods o f analysis.

M erck w as the first m anufacturer in this country to pro d u ce laboratory chem icals co n fo rm in g to definite stan d ard s, and w as also the first m anufacturer to publish m eth o d s o f testin g them . T h ese tests o rig in ally ap p eared in th e 1907 ed itio n o f M erck ’s Index. W ith the g rad u al im pro v em en t in m anu­

facturing p rocesses and m ethods o f testin g , th e quality stan d ­ ards o f M erck’s L aboratory Chem icals have been c o rre sp o n d ­ ingly raised an d the m ethods o f testin g b ro u g h t up to date.

I f you w ant C.P. chem icals co n fo rm in g to definite p u blished stan d ard s and tested by definite pub lish ed tests—

D o n o t specify “ C .P .” only— s p e c ify "C .P . M E R C K "

MERCK & CO. ^I

^{n c}

^.

M a n u f a c tu r in g C h e m is ts

Rahw ay, N . J.

September 15, 1933 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 9

This will

change your ideas

ABOUT FILTER PAPER

IF YOU H AVE NOT RECEIVED A COPY OF THE NEW 1933 BAKER & ADAMSON CATALO G _ _ _ _ _ _______________ PLACE AN ADDITIONAL CHECK M A R K ... HERE

These are challenging thoughts.

S PE ED plus H IG H E F F I - C IEN C Y in ONE paper, for all needs! . . . Can it be? Experi­

m ent, and convince yourself.

Test B & A F ilter Paper against your usual standards. I t will open your eyes.

Do you cling to the old idea of different papers for fine and coarse precipitates?

Or do you (unknowingly) use a low efficiency paper because speed is im portant? I t ’s all out of date thinking!

Baker & Adamson offers you IN ONE SINGLE GRADE of F IL T E R PA PER

•f H I G H R E T E N T I O N E F F I C I E N C Y - a s close to 100% a s is re q u ir e d in 9 9 % o f q u a n t ita tiv e a n a ly sis, ev e n w ith fine B a riu m S u lp h a te p r e c ip ita te .

S P E E D —t h a t f a r ex ceed s a n y th in g y o u ’ve ev e r e x p e rie n c e d in fine p r e c ip ita te filtr a tio n

—a n d j u s t a s s a tis f a c ­ t o r y in r o u tin e w o rk , o r w ith tro u b le so m e p r e c ip ita te s su c h as I r o n o r A lu m in u m . 2 S T R E N G T H —in a m p le

' m e a s u re for a ll p r a c tic a l r e q u ire m e n ts , p a r t i c u ­ la r ly w h e n th e p a p e r ’s speed is c o n s id e re d .

BAKER & ADAMSON DIVISION

GENERAL CHEMICAL COMPANY

40 Rector Street New York

Send me your F R E E SAMPLE EN V ELO PE of B & A Filter Paper Circles, which I will test for a personal observation of its speed and efficiency.

CELITE ANALYTICAL FILTER AID

Insuring positive clarification . . . at highest flow rates . . .fo r analytical determinations involving filtration

I t h as been one y e a r since Jo h n s- M a n v i l l e a n ­ n o u n ce d th e new C elite A n a ly tic a l F ilte r A id to th e chem ical a n d re­

search la b o ra ­ tories th ro u g h o u t th e c o u n try . T h e re c ep tio n o f th is new purified filter aid , as in d ic a te d b y le tte rs from th e m a n y ch em ists a n d o th e rs w ho h a v e ex am in ed it, has been m o st g ra tify in g a n d has ju stifie d th e decision o f J - M to c o n tin u e to su p p ly it for th o se re q u irin g a filter aid o f ex tre m e p u r ity a n d general su ita b ility for th e difficult filtra tio n s e n c o u n ­ te re d in a n a ly tic a l, rese arch a n d b acteriological w ork.

J - M C elite A n aly tica l F ilte r A id is u n iq u e in th a t it offers th e la b o ra to ry ch e m ist a p re p a re d , re a d y - for - use, d ia to m a ce o u s silica filter aid o f ex tre m e p u rity , in e rtn ess, a n d b e s t filtra tio n c h a ra c te ristic s. C hem ical tr e a t­

m e n t, w ashing, a n d c a lc in atio n h av e , in a d d itio n to fixing th e in te g rity o f th e d ia to m s tr u c tu re (an o u ts ta n d in g fe a tu re o f th e w ell-know n J - M F ilte r A ids—

F ilte r-C e l, S ta n d a rd S uper-C el, a n d H yflo-S uper-C el) elim in a te d c e rta in n a tu ra lly o c c u rrin g sub­

sta n c e s to fit th is p ro d u c t for q u a n tita tiv e uses.

A t th e sam e tim e J - M C elite A n aly tica l F ilte r A id gives th e m o st ra p id filtra tio n ra te s o b ta in ­ able c o in cid e n ta lly w ith b rillia n t c la rity in a w ide v a rie ty o f uses.

I t s o u ts ta n d in g v a lu e is in re-

6 Typical Difficult Filtrations

speeded up a n d c la rified w ith J - M C E L I T E A N A L Y T I C A L

F I L T E R A I D

(1 ) Freshly Precipitated M etastannic A d d in N itric A c id Solution: T h is suspension, w hen filtered th ro u g h N o. 40 W hatm an p ap er eith er w ith o r w ithout suction yields a tu rb id filtrate at a slow rate. W ith a d d itio n o f 1% o f the A nalytical Filter A id a rap id rate is o b tain ed w ith very clear filtrate even w ith no suction.

(2 ) Finely D ivid ed Sulphur in W ater Suspen­

sion: T h e finely divided precipitate o f sulphur form ed w hen h y d ro g en sulphide is ab so rb ed in w ater can n o t readily be rem oved by filtra­

tio n th ro u g h filter paper. W ith ad d itio n of 1% o f A nalytical Filter A id the finely divided su lphur is com pletely rem oved o n a N o . 40 W hatm an p ap er w ithout suction.

(3 ) In the d eterm in atio n o f o r the rem oval o f co llo id al silica the in c o rp o ra tio n o f a m inute quantity o f A nalytical Filter Aid m aterial assists th e filtration.

(4 ) T h e am m onium -phosphom olybdate p re ­ cip itate in th e d eterm in atio n o f p h o sp h o ro u s is difficult to rem ove by o rd in a ry m eans.

T h is filtration is easily accom plished by in ­ c o rp o ra tin g a sm all am ount o f A nalytical F ilter Aid in the sam ple before o r after p re ­ cipitation.

(5 ) C elite A nalytical F ilter A id is particularly effective in assisting the filtration o f any o f the co llo id al m etal sulphides.

(6 ) In the d eterm in atio n o f casein in m ilk C elite A nalytical F ilter A id has p ro v ed to be very helpful.

m o v in g g u m m y , g e la tin o u s, floc- c u le n t o r sem i-colloidal precipi­

ta te s from a n y susp en sio n n o t stro n g ly a lk alin e o r c o n tain in g hy d ro flu o ric acid. M a n y such su spensions w hich will qu ick ly clog a filter p a p e r o r c lo th — or c a n n o t be clarified b y th is m e an s— can re a d ily be filtered a t a good r a te o f flow to yield a b rillia n tly clear filtra te w hen a sm all a m o u n t o f J - M C elite A n a ly tic a l F ilte r A id is ad d e d .

W h e re d e te rm in a tio n o f th e to ta l a m o u n t o f th e su sp en d ed m a tte r is th e m a in o b je c t o f th e filtra tio n , J - M C elite A n aly tic a l F ilte r A id will p ro v e in v a lu a b le ; fo r exam ple, in th e d e te rm in a tio n o f th e a m o u n t o f su sp e n d ed m a t­

te r in sew age effluent w hich o ften c a n n o t be e n tire ly rem o v e d by th e u su a l la b o ra to ry filtra tio n m e th o d s.

I ts u se is also rec o m m en d e d in biological la b o ra to ry o p e ra tio n s in th e filtra tio n o f c u ltu re m ed ia, se ru m s a n d to x in s w here it is m o st im p o r ta n t to in tro d u c e no im p u ritie s in to o rg an ic p re p a ra ­ tio n s. A lso th e filtra tio n o f even th e m o st d elic a te e x tra c ts , p h a r ­ m a ce u tic al so lu tio n s, e tc ., ca n be a c co m p lish e d w ith p e rfe c t free­

d o m from c o n ta m in a tio n .

J - M C elite A n a ly tic a l F ilte r A id will also p ro v e useful in o p e ra tio n s n o t in v o lv in g filtra­

tio n b u t w here it fu n c tio n s, for exam ple, o n ly as a h ig h ly in e rt, p o ro u s m ass to expose a larg e d ry in g surface— as in th e m ois­

tu re d e te rm in a tio n o f n o n -v o la ­ tile, n o n -d ry in g oils, sy ru p s, etc.

P R O C E D U R E . . . T h e u su a l m e th o d o f u sin g J - M C elite A n a ly tic a l F ilte r A id is to a d d fro m 0 .2 % to 2 % o f th e F ilte r A id in w eig h t o f liq u id , s tir in to a u n ifo rm sus­

p ension a n d p o u r o n to th e c lo th o r p a p e r on th e B u c h n e r tu n n e l a p p ly in g a m o d e ra te su c tio n w hile p o u rin g . F iltra tio n s o n th e o rd in a ry fu n n el e v e n w ith o u t su c tio n a re g re a tly fa c ilita te d . T h e filtra te a t first m a y be clo u d y since it is n ecessary to b u ild u p a cak e o f filter

a id on th e c lo th before c larifica tio n becom es effective.

* * * *

O u r filtra tio n e x p e rts will g la d ly give y o u full in fo rm a ­ tio n as to th e m a n y p ra c tic a l a p p lic a tio n s o f th is filter aid in y o u r la b o ra to ry w ork. S im p ly a d d re ss y o u r in q u irie s to Jo h n s-M a n v ille , 22 E a s t 4 0 th a t M a d iso n A v en u e, N ew Y o rk C ity .

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

I n d u s t r i a l

Vo l u m e

5 A N D E N G I N E E R I N G

Se p t e m b e r

15,

N ^{u m b e r}

5 1933

C h e m i s t r y

Pu b l i s h e d b y t h e Am e r i c a n Ch e m i c a l So c i e t y Ha r i u s o.n E . Ho w e, Ed i t o h

Photometric Investigation of Nessler Reaction and W itting Method for Determination

of Ammonia in Sea W ater

H e n r y E . W i r t h a n d R e x J . R o b in s o n , U n iv e rsity o f W a sh in g to n , S e a ttle , W ash .

B

U CH (3), in his spectro- photom etric studies of th e W itting method for the determ ination of free am­

monia in o c e a n w a t e r , found th a t the Nessler reagents were insensitive to concentrations less than 0.05 mg. nitrogen per liter (in d i s t i l l e d w ater). I t was therefore deemed necessary to add a known q u antity of am­

monia if a lesser a m o u n t was originally present. Urbach (7) also has made a photometric in­

vestigation of th e Nessler reagent in distilled water and like Buch found th a t Beer’s law holds, b ut did not try concentrations less than 0.2 mg. per liter— th e region of g r e a t e s t i n t e r e s t to the oceanographer. W attenberg (8), using his direct nesslerization method, did not find this mini­

mum sensitivity in sea w ater and was able to estim ate 0.005 mg.

or less of ammonia nitrogen per

liter. Cooper (4) with W attenberg’s method but a modified reagent was able to distinguish visually between 0.000 and 0.003 mg. T he authors (-5) using an entirely different reagent were unable to determ ine less than 0.02 mg.

I t was believed th a t the inconsistent results previously mentioned were due to the varying sensitivities of the Nessler reagents employed, and in the W itting method to partial adsorption of ammonia during the precipitation of the interfering ions. If adsorption does take place, the W itting method is useless. This is of importance, as this method is otherwise th e b etter for th e determination of ammonia in sea w ater having a large plankton content. Plankton, which is believed to cause a turbidity in the sea water stand­

ards of the W attenberg method, is removed in the f itting procedure by occlusion in th e precipitate of barium sulfate, calcium carbonate, and magnesium hydroxide.

Ap p a r a t u s

The Zeiss Pulfrich (gradation) photom eter was used. In order to obtain significant variation in light absorption in the s m a l l range of ammonia concentra­

tions studied, photom eter tubes approxim ately 30 cm. long and 2.5 cm. in diam eter were con­

structed. The per cent light transm itted by the nesslerized ammonia solutions as compared with d i s t i l l e d water is read directly on the i n s t r u m e n t . Distilled w ater is p r e f e r a b l e as a reference standard since it is a f f e c t e d less by light and oxygen than a standard made of a m m o n i a - f r e e w a t e r p lu s N e s s l e r r e a g e n t as used by U r b a c h . S in c e t h e l i g h t a b s o r p t i o n of t h e N e s s l e r c o l o r is in t h e v i o l e t end of the spectrum, a s U r b a c h has s h o w n , the S-43 f i l t e r p r o ­ vided with the instrum ent was used. This filter has an effective range of 200 to 250 nn and transm its light with an average wave length of 430 w . The general form of the curves was verified by means of the S-47 filter, which has an average wave length of 470 jup. The tubes containing the ammonia and distilled w ater solutions were always inter­

changed to avoid errors owing to unequal illumination of th e two sides of the photometer. Each reading was checked by another observer so th a t a t least four readings were averaged for each sample reported in th e various figures.

Re a g e n t s a n d So l u t i o n s

Nessler reagents were made aceording to the directions given by (A) Ringer and Klingen; (B) R aben; (C) S tandard M ethods of W ater Analysis; and (D) Treadwell. All Four N essler reagents have been prepared an d

the color developed by them at low ammonia concentrations in distilled water an d in sea water has been investigated photometrically.

In distilled water, all fo u r reagents give a definite nonsensitive region, varying between 0.00 to 0.03 and 0.00 to 0.08 mg.

Treadwell’s reagent, in sea water, does not have a nonsensitive region. I t is therefore possible to determine as little as 0.003 mg. of ammonia nitrogen in sea water without resorting to the artifice of adding known amounts of n i­

trogen. The sensitivity of the Treadwell reagent increases with increasing chlorinity. W ith the Treadwell reagent it has been shown that Beer’s law does not a p p ly fo r concentrations of am m onia nitrogen less than 0.02 mg. p er liter.

There is no error due to adsorption in the W itting method fo r the determination o f ammonia in sea water.

293

294 Vol. 5, No. 5 chemicals were freed of ammonia, and ammonia-free w ater

was used a t all times.

Ri n g e ra n d Ku n g e n ( 3 ) . Add slowly ^{3 5} grams of potassium iodide in 1 0 0 ml. of water to 1 6 grams of mercuric chloride in

3 0 0 ml. of water until a permanent precipitate remains. Add

slowly ^{2 0 0} grams of potassium hydroxide in ^{6 0 0} ml. of water to the above solution.

Ra b e n ( 3 ) . Add ^{5 0} grams of potassium iodide in ^{5 0} ml. of boiling water to a boiling solution of ^{2 5} grams of mercuric chloride in 3 0 0 ml. of water. Filter the cooled solution into

3 0 0 ml. of water containing 1 5 0 grams of potassium hydroxide, and then dilute to a liter.

St a n d a r d Me t h o d s o p Wa t e r An a l y s i s (1). To 50 grams of potassium iodide in 35 ml. of cold water add a saturated mercuric chloride solution until a B li g h t precipitate persists.

Add 400 ml. of 9 N potassium hydroxide and dilute to one liter.

T r e a d w e ll (6). Dissolve 115 grams of mercuric iodide and 80 grams of potassium iodide in enough water to make 500 ml.

Ada 500 ml. of 6 N sodium hydroxide.

The concentrations are compared in th e following table:

Ta b l e I. Co n c e n t r a t i o n s o f Va r i o u s Ne s s l e r Re a g e n t s Re a g e n t

R in g e r a n d K lin g e n R a b e n

S ta n d a r d M e th o d s T re a d w e ll

Co n c e n t r a t i o n Hr

(aa KjHgl*?)

0 .0 5 9 M 0 .0 9 2 AT 0 .0 9 M (a p p ro x .) 0 . 2 5 AT

k

I

% it

§

1

I

IQ"O... XT—

1

\ \

i V V \

)0.

^

V \ \

\ \ ^d \ \

Li g h t Ab s o r p t i o n b y Ne s s l e r Co l o r i n Di s t i l l e d Wa t e r

The variation of light absorption in distilled w ater with varying am monia content was first determ ined one hour after nesslerization for each of th e four Nessler reagents (Figure 1). Time of color developm ent was also determined for a concentration of 0.1 mg. am m onia nitrogen per liter (Table II).

Ta b l e II. Ti m e o f De v e l o p m e n t o f Ne s s l e r Co l o r i n Di s t i l l e d Wa t e r Co n t a i n i n g 0.1 m g. Am m o n i a Ni t r o g e n

p e r Li t e r

Pe r m e a b i l i t yi n Pe r Ce n ta f t e r: (T im e in h o u rs)

0 0 . 5 1 2 26 34 50

9 4 . 0 8 4 .0 4 4 .0 3 2 .3 2 3 .0 2 4 .5 22 2

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

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

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

Hy d r o x i d e Co n c e n t r a t i o n

3 . 6 N 2 . 7 N 3 .6 N 3 . 0 N

These reagents were selected because they have all been used in th e determ ination of ammonia in sea water. The reagent of Urbach gives approxim ately the same concentra­

tion as R aben’s when 1 ml. is used per 100 ml. of w ater instead of 2 ml. per 100 ml., as is usual with th e other reagents.

W attenberg (9) suggests the use of a Nessler reagent (at­

tributed by him to Treadwell) which is approxim ately 5 N in sodium hydroxide and 0.2 M in m ercury. T he authors were unable to prepare such a reagent, as a copious pre­

cipitate was obtained when alkali was added.

HILLICRAn or MTROCCN PCX LITER

Fi g u r e 1 . Se n s i t i v i t y o f Ne s s l e r Re a g e n t s ( A , Ri n g e r a n d Ru n g e n;

B, Ra b e n; C , St a n d a r d Me t h o d s;

D, T r e a d w e l l ) i n D i s t i l l e d W a t e r U s i n g “ S - 4 3 ” F i l t e r

Thebarium chloride (200 grams of barium chloride-dihydrate perliter)and sodium hydroxide-sodium bicarbonate (200 grams of sodium hydroxide and 69 grams of sodium bicarbonate per liter) solutions were freed of ammonia by partial evapo­

ration. Ammonia-free sea w ater was prepared by adding half a volume of distilled w ater to sea w ater and evaporating to th e original volume. From this th e desired chlorinities were obtained, either by further evaporation or dilution as the case m ight be.

Re a g e n t

R in g e r a n d K lin g e n R a b e n

S ta n d a r d M e th o d s T re a d w e ll

The Treadwell and Standard M ethods reagents showed practically complete color development a t th e end of 30 minutes, whereas th e development was complete only after 5 and 10 hours in the case of th e Ringer and Klingen, and Raben reagents, respectively. The color intensity was un­

changed for 50 hours, b u t was exposed to th e photom eter light only during readings. Urbach found th a t color started to fade after 30 minutes, b u t his samples were illuminated continuously.

I t m ight be thought th a t all four Nessler reagents would give the same curve if sufficient tim e were allowed for com­

plete color development. This was not th e case. After 24 hours th e form of th e curves remained unchanged, while the nonsensitive region was reduced by only 0.01 mg. in the case of th e Ringer and Klingen and R aben reagents.

I t was thought desirable to compare these results with those in sea w ater which had been diluted with the W itting reagents. To accomplish this the am ount of ammonia actually present in th e distilled w ater was only “ /¡a of th a t indicated on th e graph.

Ac c u r a c y o f Wi t t i n g Me t h o d

To 500 ml. samples of ammonia-free sea w ater (Cl = 14.4 p arts per thousand) 0.000, 0.0025, 0.005, 0.015, 0.025, 0.04, and 0.06 mg. of nitrogen as am monia was added, the sample well shaken, and the interfering ions precipitated with 16 ml. of barium chloride solution and 32 ml. of sodium hydroxide-sodium bicarbonate. After standing one week, the clear supernatant liquid was siphoned, and 125 ml.

portions were nesslerized w ith 2.5 ml. of reagent (Standard M ethods and Treadwell). The color intensity was evaluated by means of th e photom eter after 30 minutes.

A 3500-ml. sample of th e same w ater was treated with proportionate am ounts of barium chloride and sodium hy- hydride-sodium bicarbonate solutions. T he clear liquid was siphoned and sufficient ammonia added to 125-ml.

portions to give the same concentrations as above. The permeabilities are given in Figure 2.

A ttem pts were made to speed th e settling of the precipitate by centrifugalizing, since it is desirable to analyze th e samples immediately, b u t turbidities were always obtained upon nesslerization. E vidently the precipitation is complete only on standing for several days.

If I is the value of th e scale reading (permeability in per cent) and I 0 is the value of I corresponding to zero am ­ monia concentration, then — log I/Io plotted against the ammonia content should give a straight line if Beer’s law holds for these dilutions. This has been done in Figure 3 for the Treadwell reagent, in distilled water, and sea w ater of chlorinities 10.0, 14.4, and 18.0 p arts per thousand. The plotted values for sea w ater were those obtained after first precipitating with barium chloride and sodium hydroxide-

September 15, 1933 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 295 sodium bicarbonate solutions and then adding known quan­

tities of ammonia.

To determine the ammonia content of sea water, the following procedure was used:

To 250 ml. of the sample in a 300-ml. bottle add in suc­

cession 10 ml. of barium chloride solution and 20 nil. of sodium hydroxide-sodium bicarbonate, shaking after each addition. W ith chlorinities less than 17 parts per thousand, smaller quantities of reagents were used (Cl = less than 11.0 p arts per thousand, 5 ml. BaCl2; Cl = 11.0-13.9 parts per thousand, 6.5 ml. BaCl2; Cl = 14.0-16.9 parts per thousand, 8.0 ml. BaGlj, with twice as much NaOH-

Fi g u r e 2 . Ac c u r a c y o f Wi t t i n g Me t h o di n Se a Wa t e r Us i n g " S - 4 3 ” F i l t e r ( C , S t a n d a r d M e t h o d s R e a g e n t ; D, T r e a d w e l l R e a g e n t )

A P r e c ip ita te d b efo re a d d itio n of N H i O P r e c ip ita te d a f t e r a d d itio n of N H j

NaHCOa in each case). This eliminated difficulties en­

countered in obtaining clear solutions on nesslerization, which were believed to be due to too great an excess of re­

agents. A fter standing for a t least 3 days, the supernatant liquid was siphoned and the ammonia determined photo­

metrically.

T his procedure was tested on eighteen samples taken in Hood Canal, April 29 to 30, 1933, and gave excellent results in every case. Three duplicates, which were allowed to stand for 25 days, showed 0.010 mg. more ammonia nitrogen than those tested after 10 days, indicating a probable de­

composition of organic m a tte r in the alkaline solution. This would be the greatest increase normally expected, since these samples "were especially rich in plankton. The necessity of finishing the determ ination as soon as possible after sampling is, however, evident.

Di s c u s s i o n

I t is apparent from Figure 1 th a t the various Nessler reagents have different characteristics a t low ammonia con­

centrations, b u t uniformly show a minimum sensitivity.

The form of the curve depends apparently on the concen­

tratio n of th e constituents in the reagent. As far as results in distilled w ater are concerned, the Standard Methods reagent is preferable, since it has a shorter nonsensitive region. The Treadwell reagent has too great a color of its own, and in addition, samples nesslerized with it always give a precipitate of mercuric iodide on standing. In sea water, however, the Treadwell reagent gives far better results. In th e chlorinities investigated no limiting sensitivity was apparent, b u t there was a very definite change in the log curve (Figure 3) a t N = 0.02 mg. per liter in even- case.

In addition, th e sensitivity of the reagent apparently in­

creases with increasing chlorinity.

The Standard M ethods reagent shows a definite b u t shorter nonsensitive region in sea water, b u t its use is excluded by a turbidity which always appears a t ammonia concentrations of 0.1 mg. nitrogen per liter or higher, which is not th e case with the Treadwell reagent. The Ringer and Klingen and Raben reagents are not applicable, as they develop their color too slowly, usually give a turbidity, and have large nonsensitive regions in sea w ater as «'611 as in distilled water.

Two Nessler reagents which had been prepared for 19 months were also tested, one of which, the Treadwell reagent, was much less sensitive and dependable in distilled water, b u t gave satisfactory results in sea water. The other, a Standard Methods reagent, was slightly more sensitive (distilled water) after standing, b u t was not tested in sea water.

The above Standard Methods reagent was the one used by the authors (5) in the determ ination of ammonia in sea water by the W attenberg method. As the minimum sensi­

tivity for this reagent is 0.02 mg. of nitrogen per liter, the inability of the authors to detect less than this quantity is thus explained. Moreover, it should be noted th a t this minimum sensitivity likewise applies to th e determination of Kjeldahl and albuminoid nitrogen in w ater so th a t a zero blank does not necessarily mean there is no ammonia, but merely th a t 0.02 mg. or less of nitrogen per liter is present.

F i g u r e 3 . A p p l i c a b i l i t y o f B e e r ’s L a w t o N e s s l e r R e a c t i o n U s i n g T r e a d w e l l R e a g e n t a n d S m a l l C o n c e n t r a t i o n s o f A m m o n i a i n D i s ­ t i l l e d W a t e r (D) a n d S e a W a t e r o f V a r y i n g C h l o r i n i t y ( C = 1 0 ,

B *» 1 4 .4 , A = 1 8 P a r t s C J p e r T h o u s a n d )

Figure 2 shows th a t there is no significant adsorption of ammonia on the precipitate, as in m ost cases th e values by th e two methods agree within 0.005 mg. The W itting method can therefore be used in sea w ater w ith little error arising from this source. Furtherm ore, it is possible to obtain an accurate standard curve by addition of known quantities of ammonia to sea water from which th e inter­

fering ions have previously been removed. Figure 2 also shows th a t, w ith th e Treadwell reagent, it is possible to determine directly as little as 0.003 mg. of am monia nitrogen per liter w ithout resort to th e artifice of adding 0.05 mg. of nitrogen to each sample.

I t has been observed by th e authors, and also by B raarud and Klem (¿8) th a t artificial ammonia-free sea w ater as prepared in the above experiments gives a slight color with the Nessler reagent which is not obtained with naturally occurring ammonia-free water. Where possible, therefore, it is desirable to make standards from untreated am m onia-

A N A L Y T I C A L E D I T I O N Vol. 5, No. 5 free sea water, which in the P uget Sound region is m ost ap t

to be found in the surface waters.

Li t e r a t u r e Ci t e d

(1) Am. Pub. Health Assoc. N. Y., Standard Methods of Water Analysis, 7th ed.. 1933.

(2) Braarud, T., and Klein, A., Iivalradets Skrifter Norske Viden- skaps-Akad. Oslo, 1, 50 (1931).

(3) Buch, K., Rapp. proc. verb, reunion, conseil perm, intern, explor.

mer., 53, 36 (1929).

(4) Cooper, L. H. N., J. Marine Biol. Assoc. United Kingdom, 18, No. 2, 719 (1933).

(5) Robinson, R. J., and Wirth, H. E., J. conseil intern, exploration mer. Accepted for publication.

(6) Treadwell and Hall, “Analytical Chemistry,” 6th ed., Vol. I, Wiley, 1927.

(7) Urbach, C., Mikrochemie, 11, 50 (1032).

(8) Wattenberg, H., Ann. der Hydrog. Marit. Meteorol., 59, 95 (1931).

(9) Wattenberg, H., Rapp. proc. verb, reunion, conseil perm, intern.

explor. mer., 53, 108 (1929).

Re c e i v e dJ u ly 3 , 1 9 3 3 .

X -Ray M ethod for Q uantitative Comparison of Crystallite Orientation in Cellulose

Fibers

W a y n e A . S i s s o n 1 a n d G e o r g e L . C l a r k , D e p a rtm e n t o f C h e m istry , U n iv e rs ity o f Illinois, U rb a n a , 111.

T

H AT the orientation of the cellulose structural units varies w id e l y in different fibers and in the same fiber (1, 8) is well known, and its influence upon the physical and chemical properties of th e fiber has been discussed b y many investigators (15, 23), particu­

larly w ith reference to the degree o f m e r c e r i z a t i o n , t e n s i l e s t r e n g t h , classification, elas­

ticity, and dyeing properties of cotton (5, 6 ,19, 81); the swell­

ing, elasticity, tensile strength, ability to take dyes, resistance to e n z y m a t i c decomposition, gloss, creasing resistance, refrac­

tive index, and extension of rayon (3, 5, 7, 9 ,1 1,18,19, 21,22,28);

and th e density, tensile strength, e x p a n s i o n , and shrinkage of wood (1, 17, 82).

The use of x-rays in studying this orientation and differenti­

ating b e t w e e n the v a r i o u s textile fibers, especially rayon,

has been described by Clark (5), M ark (20), and others.

These investigators, however, used a visual m ethod of com­

paring the x-ray patterns which is essentially qualitative in nature. I t is the purpose of this paper to describe briefly an im provem ent over th e visual m ethod, which enables a quantitative comparison to be made, and to point out the possible applications of the method.

T he improved m ethod is based on a comparison, for differ­

en t samples, of the relative intensity distribution along the circle on which th e 002 interference maxima are localized.

Although th e significance of cellulose fiber diagrams has been developed by Polanyi and Weissenberg (26, 27) and the rela­

tion between crystal orientation and sharpness of th e localized maxima is explained in textbooks on x-rays (2, 4), the basis of th e m ethod m ay be explained briefly as follows:

Figure 1 shows typical x-ray p atterns of a cellulose sheet and a bundle of ramie fibers. In both patterns the most intense interference (.4j line) is due to the 002 planes (24).

1 S en io r T e x tile F o u n d a tio n Fellow .

Since these planes are parallel to the long axis of the crystallites (24, 35), each plane a t angle 0 to th e x-ray beam (fulfilling the conditions of the Bragg equation n \ — 2d sin 6) w ill d i f f r a c t x-rays in the limiting case, upon the 002 diffraction ring a t right angles to th e long axis of the crystallite. The diffraction ring registered on th e photographic film is thus a sum m ation of the individual diffractions from all the diffracting crystallites, and a comparison of the intensity dis­

tribution around this ring gives a measure of th e distribution of the crystallites around the pencil of x-rays. F or a complete pic­

ture of the orientation in any sample it is necessary to obtain an x-ray p attern w ith the sample i n c l i n e d a t v a r i o u s a n g l e s to th e x-ray beam. However, for comparing the orientation of different fibers, one p a tte rn taken w i t h t h e x - r a y b e a m perpendicular to th e fiber axis is sufficient. A perfectly uni­

formly intense 002 diffraction ring, such as th a t obtained with th e x-ray beam perpendicular to the cellulose sheet, implies th a t the long axes of the crystallites have a random orienta­

tion in th e plane of th e sheet. If th e intensity is concen­

trated into localized maxima, as is th e case for the x-ray beam perpendicular to the ramie fibers, then the crystallites ap­

proach a parallel arrangem ent along the fiber axis.

Ex p e r i m e n t a l

T he intensity m easurem ents are made on a microdensitome­

te r of the “ photograph wedge” type, the principle of which was first described by H artm an (14) and more recently by Vasil’ev (86). I t is m anufactured by the G aertner Scientific Corporation and involves some novel features. The wedge used is not strictly a photographic wedge b u t a dyed gelatin wedge between glass plates. This is essential in order to give the necessary linear relation between density and scale read­

ings. T o make up for the lack of grain of this type wedge a The relation between orientation of the crystal­

lites or micelles an d various properties of cellulose fibers is poin ted out an d an x-ray method fo r quantitatively comparing the orientation is described. The method is based upon the as­

su m ption that the distribution of the crystallites around the pen cil of x-rays is proportional to the distribution o f in ten sity around the 002 diffraction ring. In ten sity measurements are m ade with a microdensitomeler equipped w ith a rotating stage.

The distribution of the crystallites is calculated from the intensity values an d the orientation is expressed by distribution curves which m a y be differentiated fro m one another by statistical methods. The data obtained m a y be used to stu dy the structure of the fiber or to predict ph ysical an d chemical properties which are anisotropic. T yp ica l data fo r three grades o f cotton are presented to show the sensitiveness of the method.

September 15, 1933 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 297 grain plate is placed a t the focus of the comparison microscope

which makes it unnecessary to defocus the microscope viewing the spectrum line. The shifting of the cube which was pres­

ent in the original H artm an microdensitometer has been eliminated by utilizing a short vertical slit a t the silvered horizontal strip of the dividing surface. The readings, which are read from a scale dividing arbitary units from 0 to

\ 002 / Ring

Equator Line

Cellulose Sheet Ramie Fibers

Fi g u r e 1. X -R ay Pa t t e r n Il l u s t r a t i n g Ra n d o m a n d Pr e­ f e r r e d Or i e n t a t i o n

100, are proportional to the densities and consequently to the logarithm of the reciprocal of th a t portion of the light transm itted. The wedge type is more satisfactory than the registering type of microphotometer (12, 13, 33), since it gives definite, duplicable values for the intensity which may be used as th e basis of calculations. A special calibrated rotating stage was constructed which allows the film to be rotated through 360° with th e microdensitometer focused on the 002 line. The area included in the measurement is about 0.05 nun. wide and 0.8 mm. long, the long dimension being across the diffraction ring and including about one-half to two-thirds the w idth of th e ring. The position of the film in focus may be read directly from the stage. Figure 2 shows the microdensi­

tom eter equipped w ith the rotating stage.

Although the planes which are parallel to the fiber axis diffract on the “ equator line,” a t right angles to the fiber, the equator line will be referred to as the 0° position in order to avoid confusion in this discussion. Readings may be made every 2°, 5°, or 10°, depending upon the accuracy desired.

Fi g u r e 2 . Mi c r o d e n s i t o m e t e r Eq u i p p e d w i t h Ro t a t i n g St a g e

Readings every 5° are satisfactory for most purposes and the num ber of these made in each quadrant will depend also upon the accuracy desired. In order to eliminate errors due to failure to m ount the film and sample perpendicular to the x-ray beam, uneven scattering, or the slightly off-center position of th e film on the stage, readings should be made over a 360° range in every case. A typical data sheet is shown in Table I.

In this table, and also in data given elsewhere, the angles ending in 0 are read in two quadrants and those ending in 5 in opposite quadrants. This gives two readings every 5° which

4 0 38 J i 3 4

IZ

3 0

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Fi g u r e 3 . Ef f e c t o f Ti m e o f Ex p o s u r e o n Me a s u r e d In t e n s i t y Cu r v e s

(X -ra y p h o to g ra p h s r e p r e s e n t tim e s of e x p o s u re c o rre s p o n d in g to c u rv e s )

are averaged. If more accurate d ata are desired four readings for each 5° angle should be averaged.

Ta b l e I . Ty p i c a l Da t a Sh e e t S a m p le 3 5 1 ( c o t t o n ) Re a d in g s ( Qu a d r a n t)

An g l e 1 2 3 4 Av e r a g e Co r r e c t e d %

0 4 2 . 6 4 2 . 0 4 2 . 3 3 4 . 0 1 2 . 0 0

5 4 Ü 8 4 i 18 4 1 . 8 3 3 . 5 1 1 .9 0

10 4 Ü 4 4 Ü 4 4 1 . 4 3 3 . 1 1 1 . 7 0

15 4 0 ! 2 4 1 .0 4 0 . 6 3 2 . 3 1 1 . 4 0

20 3 8 ^ 0 3 8 .*6 3 8 . 3 3 0 . 0 1 0 . 6 0

25 3 5 .*6 3 0 . 4 3 6 . 0 2 7 . 7 9 . 8 0

3 0 3 0 .‘ 0 3 Ô Ï6 3 0 . 3 2 2 . 0 7 . 8 0

35 27'.5 2 8 ^ 6 2 7 . 0 1 8 . 7 6 . 6 3

40 2 1 .6 2 i ! 6 2 1 . 6 1 3 . 3 4 . 7 1

45 1 S .2 1 9 .0 1 8 . 6 1 0 . 3 3 . 6 5

50 1 5 .2 1 3 ^ 8 1 4 . 5 6 . 2 2 . 2 0

55 1 3 .6 1 3 ! 1 3 . 3 5 . 0 1 . 7 7

6 0 1 i 16 1 2 ! 2 1 1 .9 3 . 6 1 . 2 7

6 5 i i ! o 1 i 16 1 1 . 3 2 . 9 1 . 0 3

7 0 1 0 .2 10.' 4 1 0 . 2 1 . 9 0 . 6 7

7 5 1 i 12 li . ’ o ^{1 1 .1 2 . 8 0 . 9 9}

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

8 5 9 . 6 1ÔI2 ^{9 . 9 1 . 6 0 . 5 7}

9 0 1 0 . 0 1 0 . 0 . . . . 1 0 . 0 1 . 7

T o t a l 2 8 2 . 3

~ .. 8 .5 + 8 .0 + 8 .5 + 8 .2 C o r r e c t i o n » --- '--- '--- «■ 8 .3

0 . 6 0

A correction for the scattered radiation m ust be subtracted from the average reading, and this m ay be obtained by reading the intensity on the lightest portion of the film be­

tween the 002 line and the next line of larger diam eter for each quadrant and taking the average as the correction factor.

The corrected readings are then converted to a percentage basis. Representing the data on a percentage basis eliminates the necessity of carefully controlling such experimental variables as time of exposure, intensity of the x-ray beam, thickness of sample, as well as the tem perature and tim e of developing. These factors, however, should be held constant for accurate work.