4 S D E-VGISEERI-VG C H E M I S T R Y Vniversity, Kingston. Ontario. n o x Metals Department, Deloro Mining & Reduction Company, Deloro, Ontario. The authors wish hereby t o acknowledge their indebtedness t o these gentlemen, a n d as well t o l f r . R . C. Wilcox, Research Laboratory. Queens UnLrersity, Kingston. Ont., now analyst, T h e Exolon Company Thorold. Ontario. b y whom most of t h e analyses reported in this paper m-ere made. 156
SIXTH
STREET, CAXBRIDGE,hZ.455ACHUSETTS
NOTES UPON OIL TESTING B y ACGUSTUSH. GILL Receired October 21, 1916
I-A
T E S r F O R OILS BY SALTING-OUT T H E I R SOAPS
I t is a well known fact t o t h e commercial soap maker t h a t different soap stocks require varying amounts of salt for t h e “salting o u t ” process. I t occurred t o t h e writer t h a t if this could be made quantitative, i t would form a n additional criterion by which t o judge of t h e purity or genuineness of a n oil. Reference t o t h e literature revealed t h e fact t h a t this principle h a d already been made use of by Carpenter’ for detecting t h e presence of cocoanut a n d palm oils i n soaps. Soap from ordinary oils requires from 8 t o I O cc. of a s a t u r a t e d solution of salt, whereas t h a t from cocoanut oil may require jo cc. T h e procedure is as follows: 2 g. of t h e oil are saponified with j cc. of I O per cent caustic soda, adding alcohol if necessary. Evaporate t o dryness on a water b a t h . dissolve t h e soap in warm water, cool, neutralize with hydrochloric acid. using phenolphthalein as a n indicator, a n d make u p t o jo C C . T i t r a t e I O cc. of this solution with salt solution ( 3 2 0 g. t o t h e liter) i n a bottle after t h e manner of t h e determination of hardness in water until t h e lather obtained just does not persist for five minutes. F r o m t h e HC1 used, a n d this titration with salt, calculate t h e grams of salt necessary t o precipitate t h e soap found from I g. of oil. T h e following results were obtained : T ~ B LI-GRAMS I~ NaCl P E R GRAMOIL Oil I I1 P u r e olive . . . . . . . . . . . . . . . . . 2.2 2.1 11.6 Suspected sample Olive F o o t s ( ? ) , , , , , , , , . , . , , 1 0 . 6 Cottonseed.. . . . . . . . . . . . . . . 8.0 8.6 Linseed . . . . . . . . . . . . . . . . . . . 1 4 . 6 12.9 Oleomargarine.. . . . . . . . . . . . 2.8 2.8 Butter . . . . . . . . . . . . . . . . . . . 1.4 1.2 C o c o a n u t . , . . . . . . . . . . . . . . . . S o end point obtainable.
T h a t something was really wrong with t h e olive foots 11-as evident from t h e f a c t t h a t i n making soap from
t h e m i n a large way, i t h a d t o be “broken” twice a n d t h a t nearly double t h e usual q u a n t i t y of salt was required. 11-.4
TEST FOR GELATIKOUS MATTER I N L I S S E E D OILS
I n determining unsaponifiable matter i n linseed oil, it was noticed t h a t a white, cotton-like-looking cloud formed between t h e soap solution a n d t h e supernatant layer of gasoline. It was further noticed t h a t t h e oils which showed t h e greatest a m o u n t of this cloud or sludge were slowest in drying a n d gave t h e roughest, 1 W. L a n t Carpenter, Allen’s “Commercial (1910), 436
Organic Analysis,”
2
Yol. 9. S o .
2
dullest and least elastic surfaces. particularly in patent leather finishes. T h e procedure is as follows: Saponify I O g of the oil with 2 0 cc. I O per cent caustic soda, b y heating in a 6 in. porcelain dish over a low flame. .idd x a r m water when necessary a n d boil until saponification is complete. Make u p t h e soap solution t o 2 2 5 cc. in a graduate with warm distilled mater. Warm water should be used t o prevent t h e hydrolysis of t h e soap. Pour out 2 5 cc. into a 6 in. test t u b e , seven-eighths t o one inch i n diameter, a d d 8 cc. of 8 6 ” gasoline (from Pennsylvania crude) a n d shake thoroughly. Whirl in a centrifuge a t 1800 r. p. m. for 3 min. by t h e watch a n d observe t h e amount of sludge t h a t forms between t h e layers. Ordinary linseed oil gives a sludge nearly I O nim. i n thickness or more, while a n artist’s oil which had been thoroughly washed with water a n d allowed t o s t a n d a n d settle gaye less t h a n j m m . which is t h e smallest amount ever seen i n a linseed oil. The first linseed oil, on applying t h e “breaking“ test, “broke” a t about 2 9 j 0 C., while t h e artist’s oil did not “break” below 300’ C. Attempts t o remove all t h e sludge b y centrifuging repeatedly ( u p t o nine times i n one instance) with fresh gasoline were unsuccessful. More sludge was found i n t h e ninth t h a n i n t h e first centrifuging. The first time, however, gives comparative results. Xtt e m p t s t o make t h e test quantitative b y collecting a n d weighing on a tared filter were also unsuccessful. I~ASSACHCSETTS INSTITUTE OF TECHXOLOGY, CAMBRIDGE
COLOR TESTS FOR OILS-PALM
OIL
. B y AUGUSTUSH. GILL Received October 21, 1916
The chemist uninitiated in this subject would infer t h a t color tests for different oils rest upon t h e same firm basis as those for copper, iron or chromiumparticularly after hearing testimony i n certain legal cases. P a l m oil is positiT7ely sworn t o - n o t something giving reactions like palm oil-and this. on t h e strength of a single reaction lasting less t h a n t e n seconds! Speaking from a n experience of over t h i r t y years, a n d from extensive a n d careful reading, this is not t h e case-color tests are merely circumstantial evidence. If a color test be obtained, there is a p r o b a b i l i t y t h a t a certain oil is present, b u t no certairtty. Xor can any positive conclusions be drawn from any one test, save t h a t of isolating unsaponifiable oil; one must have t h e evidence of several different tests, each confirming t h e other. Nor can a n y other conclusion be possible. The oils are products of organic life, a n d this is dependent upon conditions of growth, i n t h e case of a vegetable oil, as t o whether t h e season be wet or d r y , warm or cold, t h e fruit be underripe, fully ripe or overripe; a n d in t h e case of a n animal oil, upon t h e feed. A hog fed on corn gives lard of a higher titer test a n d lower iodine value t h a n one fed on mast. Similarly, cows fed upon cotton or sesame cake give milk, t h e f a t of which responds t o t h e same color tests as do
Feb.. 1917
T H E J O U R S d L OF I S D C S T R I A L A S D ESGI&VEERISGC H E M I S T R Y
cotton and sesame oil. T o complicate further matters, we have t h e different varieties of the same fruit: e . g., t h e olive, of which there are 300 different varieties in Italy alone, which yield oils which differ among themselves. Instead of wondering t h a t the chemist cannot do more, t h e marvel is t h a t he does as me11 as he does. T h e color tests upon which come dependence may be placed are few, a n d are as follows: Halphen test for Cottonseed Oil. Becchi test for Cottonseed Oil. Baudouin test for Sesame Oil. Liebermann-Storch test for Rosin Oil. Crampton-Simons test for Palm Oil (until recently). T H E H A L P H E N TE:STis probably t h e best test for cottonseed oil, and one of t h e more clearly marked a n d characteristic color tests. I t is, however, also given b y Kapok oil' (which comes from a related plant) which is used as a n edible oil where the plant is grown -in China, E a s t and West Indies, a n d in Africa. Baobab oil' also responds t o it even more strongly t h a n cottonseed. On the other h a n d , a negative Halphen test is no proof of t h e absence of cottonseed oil, as old rancid oil, one which has been heated t o 2 0 o - 2 2 o 0 , or has been blown, does not give t h e test. Lewkowitsch says:2 " I t should be distinctly understood t h a t color reactions taken b y themselves should not be relied upon as gilring a decisive answer. At best t h e y can be used only as a preliminary test, or as a confirmatory test. T h e ease with which this test can be carried o u t , a n d its apparent reliability, have led t o a n overestimation of this very useful a n d important reaction; so much so t h a t grave errors m a y be committed b y those who assign t o this test an exclusive or even a paramount importance. I t is altogether unjustifiable t o look upon this test, as has been done, as permitting of q u a n t i t a t i r e interpreta.tion." I t is not k n o r n what is t h e cause of t h e reaction. T H E B E C C H I ( O R S I L V E R T I T R A T E TEST)---Here t h e statements contained in t h e literature are r e r y conflicting. Eminent authorities hax-e pronounced both in favor of and against it. I t is, howev-er. t o be noted t h a t absolutely pure lard, t u n g and olive oil are n o t infrequently met with which give t h e t e s t ; consequently its indications cannot be considered as conclusive . The substance which gives the reaction is supposed to be aldehydic i n its nature-this receives some support from the fact t h a t a body of a phenolic nature, Gossypiol, has been discovered in t h e color from cottonseed hulls. T H E CAUOIS-B.AUDOUIS T E S T is probably the most reliable of all the color tests. I t should be noted, h o n ever, t h a t it is also given b y olil-e oils of Bari. Brindisi and Lecce. b u t not b y t h e f a t t y acids obtained from t h e m . Furthermore. certain permissible butter colors respond t o the test. Rancid sesame oil m d some extracted b y chloroform failed t o respond. The subllilliau, campi. v e i i d . , 139 (1901), 80:. "Chem. Technology and Analysi- of Fats, Oil, Ed., 2 (1914), 203.
and \Taxes,"
5th
1.37
stance which gives t h e reaction seems t o be a thick non-crystallizable oil free from nitrogen.' T H E L I E B E R ~ I A K X - S T OTR EC S TH is a reliable test for rosin oil, b u t is not conclusiire, as cholesterol gives t h e same color, which is fugitive. The substance which gives the reaction is unknown. T H E CR.AMPTOK-SI310NS T E S T F O R P h L M OIL-LelYkowitsch, in his last edition. says: "These color tests appear t o t h e author t o be very uncertain." T h e test was published in 1 9 0 j 2 and is carried out b y t h e De9 CC. of partment of Internal Revenue as the filtered fat are placedin a I j cm. tube and ,3 cc. of t h e subsequently described acetic anhydride reagent is added. The t u b e is then vigorously shaken for from j t o I O seconds. T h e color of t h e emulsion should be noted, as a bluishgreencolor is indicative of the presence of palm oil. T h e t u b e is then placed into a centrifuge a n d whirled for from j t o I O seconds at about I j o o t o 2 0 0 0 r. p. m. I t is t h e n taken out a n d noticed t h a t t h e t u b e has t h e appearance of two layers, the acetic anhydride in th,e bottom of the tube as i t was before shaking, and the fats above. T h e color of t h e lower layer a t this point should be noted. light blue is indicative of t h e presence of palm oil. One drop of sulfuric acid, specific gravity I . j 3 >is added t o t h e tube. Previous to the addition of t h e sulfuric acid a t this point t h e analyst should place himself in t h e best light possible in t h e laboratory. An overhead light, such as a skylight, is t h e preferable sort of light in order t o read t h e colors. ,\fter adding a drop of sulfuric acid t h e t u b e is inverted and immediately returned t o its former position: as the drops of t h e acetic anhydride, which formed the lower layer, drop back, the color is noted. The acid has changed this acetic anhydride t o a fairly deep blue. This is proof of the presence of palm oil. It is t o be noted in making this determination t h a t several precautions are necessary: we must have experience, and t h e proper temperature of the fat, pure reagents and speedy manipulation, as t h e color changes so fast t h a t the test has t o be carried o u t from beginning t o end in as short n time as possible. The acetic anhydride reagent is made by adding t o j o cc. of C. P. acetic anhydride. one drop of sulfuric acid. specific gravity 1 . j 3 . Then the mixture is shaken and must s t a n d j minutes before being used, as the reagent should not be used if i t has stood ox-er 30 minutes. Experience has taught tis t h a t t h e reagent is not sensitix-e for use before j minutes standing a n d is not sensitive for use after 30 minutes. The filtered fat previously described is brought t o a temperature of about 3 j o . This point is x-ery necessary because x e have found b y experience t h a t temperatures below this do not work very satisfactorily, or very much above i t . T h e procedure inrolving the use of acetic anhydride has been criticized b y the Association of Official Agricultural Chemists as follows:' Villavecchia and Fabris, J . .So[. Chem. l i ! d , 13 ( 1891), 6 9 . J. A m . Chem. Soc., 2 1 , 270. 3 F r o m court record 19 15. Bryan a n a Gardner, Proc. A . 0. A . C . , 1910, 9 0 ; Bull. 137, U. S . Department of Agriculture. 1
2
138
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 9 ,
KO.2
“ T h e test described is not satisfactory for t h e fol- bisulfide solution was added t o cottonseed oil, t h e lowing reasons: solvent evaporated below 70°, t h e oil tested, a n d i t (I (a) Other oils t h a n palm oil give colors which are gave t h e characteristic blue color, although no palm easily mistaken for t h e palm oil test. oil was present. T h e f a t t y acids from palm oil soap “ ( b ) T h e color produced is not permanent. It solution which h a d been extracted with carbon bichanges a n d fades so rapidly t h a t i t is very difficult sulfide, on t h e other hand, did not give t h e usual blue t o recognize it. color, showing t h a t t h e substance producing i t h a d 1‘ (c) T h e test is not definite, as there is little difference been completely removed b y t h e carbon bisulfide. in t h e color produced when palm oil i s present a n d Carotin, according t o Willstatter a n d Stoll,’,has t h e when i t is absent. formula C40H56, crystallizes either i n rhombohedrons I< ( d ) T h e color produced is changed so much by or plates, with a coppery or blue sheen. It melts at slightly varying t h e a m o u n t or strength of t h e sul- 174’ (corr.), is difficultly soluble i n methyl a n d ethyl furic acid used.” alcohol, acetone a n d petroleum ether, b u t readily T h e authors s t a t e , a n d this has been substantiated dissolves in benzol a n d carbon bisulfide. It i s a n b y numerous others, t h a t similar reactions are given unsaturated body (absorbing halogens) a n d a u t o by mustard a n d sesame oils, a n d t h a t t h e latter can oxidizable. This would account for t h e bleaching be washed out b y alcohol. of palm oil b y light. It dissolves i n concentrated A blue color obtained b y t h e Revenue test, therefore, sulfuric acid with t h e formation of a n indigo-blue could equally well be d u e t o t h e sesame oil, as no color. It is further interesting from the f a c t t h a t requirement of washing with alcohol is mentioned. i t is one of t h e few colored hydrocarbons. F u r t h e r objections to t h e test are, t h a t different T h a t t h e substance extracted from palm oil was chemists, skilled in t h e a r t , get different results a n d really carotin would seem t o be shown b y t h e followhave difficulty in duplicating their own results. This ing tests, being t h e same as employed b y Palmer a n d was shown i n a recent case which came t o t h e writer’s Eckles in their work.* notice; numerous samples ( u p t o 56 in some cases) I-By the absorption spectrum: Tested i n t h e were submitted t o six different chemists, three technical Krhss single-prism spectroscope, according t o t h e men, one a former employee of t h e Revenue Bureau method of Formanek,s t h e readings given below were a n d another Doctor C r a m p t o n himself, three university obtained for t h e e n d towards t h e red of t h e absorption professors, a n d there was practically no agreement band between t h e E a n d F lines. In CS, In alcohol among t h e m . Certainly i t has no claims t o reliability solution solution or t o be classed even with t h e Becchi test. 14.13 Carotin from carrots.. . , , . , , , , . . . 13.64 13.25 14.34 Carotin from palm o i l . . . . . . . . . . . I n addition t o t h e interfering oils, mustard a n d 14.62 Carotin from grass. . . . . . . . . . . . . . 13.43 sesame, i t is interesting t o note t h a t t h e test is sometimes T h e solutions of carotin, from carrots, from palm given b y linseed oil, b u t not b y rosin or rosin oils. oil a n d from grass, s h u t off t h e portion of t h e spectrum I n trying t o ascertain t h e cause of this test a n d of subtoward t h e violet end very sharply, as if a card h a d stances present in oleomargarine a n d likely t o produce been placed between t h e instrument a n d t h e bottle i t , t h e s t a t e m e n t was found i n one of t h e quasicontaining t h e solution. T h e agreement, although scientific papers t h a t t h e yellow color of b u t t e r a n d somewhat divergent mathematically, is regarded as certain animal fats a n d oils was due to carotin;* this satisfactory Phytosterol which might have been exsubstance was prepared b y t h e extraction of dried tracted a t t h e same time gives no absorption speccarrots with carbon bisulfide, a n d some of this solution trum. added t o cottonseed oil. T h e carbon bisulfide was 2-It is not extracted from its petroleum ether evaporated off a t a temperature below 70’ a n d t h e solution b y 80-90 per cent alcohol. resulting oil tested, when i t was found t o give t h e 3-It absorbs bromine, as does carotin. familiar blue color as if palm oil were present. Ap4-It is not adsorbed by precipitated chalk. parently t h e n i t was due t o carotin a n d not exclusively 5-It gives a deep red color in carbon bisulfide solut o palm oil as supposed. tion. T o substantiate this conclusion, a quantity of palm 6-It gives t h e s a m e blue color in acetic acid when oil was saponified with alcoholic sodium hydroxide, treated with sulfuric acid as does carotin from grass leaving a slight excess of alkali; t o ensure t h e absence a n d carotin from carrots. of free palm oil, t h e alcohol was evaporated, a n d t h e Samples of cottonseed oil which gave no test were residual soap dissolved in water a n d shaken o u t with treated with a carbon bisulfide solution of carotin carbon bisulfide; this assumed a deep red color. Both obtained from palm oil, b u t containing no palm oil, soap a n d extract were saved, t h e carbon bisulfide a n d also with a solution of carotin from carrots. T h e distilled off a n d t h e residue again treated with a n portions of carbon bisulfide evaporated off below 70’ excess of sodium hydroxide as before, t o ensure t h e a n d with palm oil were sent t o t w o different chemists, complete removal of a n y palm oil which might possibly a n d both reported t h e m t o contain palm oil. have escaped saponification. T h e resulting soap T h e a m o u n t of carotin obtained was small, as may solution was extracted with carbon bisulfide as before, 1 Willstitter and Stoll, “Untersuchungen uber Chlorophyll.” P. 241. with similar results. Some of this deep red carbon 2 J . Biol. Chcm.. 17 (19141, 190. 1 This statement was undoubtedly based on the work of Palmer and Ecklcn
8
1900.
Spektral-analytischer Nachweis kunstlicher organischer Farbstoffe,
Feb., 1917
T H E J O U R N A L O F I N D U S T R I A L A N D E NGI iV E E RI N G C H E M I S T R Y
be judged from t h e fact t h a t from jooo kilos of fresh carrots ( 4 7 2 kilos dry) Willstatter a n d Er;cherl obtained only 1 2 5 g. of carotin. This is 2 . : ; p a r t s in IOO,OOO. Chemical tests for colors not infrequently have a delicacy of one p a r t i n one billion. T h a t carotin is contained in animal fats a n d oils was abundantly s h m n b y t h e work of Palmer a n d Eckles2 i n t h e dairy laborat,ory of t h e University of Missouri, i n cooperation with t h e U. S. Department of Agriculture. T h e y showed i t to be contained i n b u t t e r f a t a n d t h e body fat obtained from cows, a n d further t h a t i t was not generated b y t h e animal, b u t absorbed from t h e feed, particularly grass. Hence, it is easy t o see why June b u t t e r is so highly colored. This work is confirmed b y t h e D e p a r t m e n t of Internal Revenue3 i n t h a t t h e test similar t o t h a t given b y palm oil would be given b y a n oleomargarine containing 20 per cent of b u t t e r or b y oleo oils. This has been further subs t a n t i a t e d by t h e work of other chemists. I n view of all these facts i t would seem t o be impossible t o prove t h e presence of palm oil b y this test for e x a m p l e i n alone i n a mixture-oleomargarine, which b u t t e r (from 5-16 per cent) a n d oleo oil (45-50 per cent) were present, since all three cont a i n t h e same substance-carotin, t o which t h e characteristic blue color is due. As a result of this work i t would seem t h a t t h e acetic anhydride or acetic acid-sulfuric acid test for palm oil. is n o longer available for use i n connection with oleomargarine for t h e following reasons: I-Unreliability of this particular t e s t , no t w o chemists agreeing upon its interpretation. 11-That t h e test is one for carotin rather t h a n palm oil a n d m a y be given b y b u t t e r , oleo oil or sesame oil-ingredients ordinarily found i n oleomargarine. 111-As applied b y t h e Revenue D e p a r t m e n t , i t is untrustworthy, because interfering oils, as sesame, are not washed out. This communication may be regarded as preliminary, as t h e subject is being further studied. MASSACEIUSETTS INSTITUTE
OF
TECHNOLOGY, CAMBRIDGE
WET COMBUSTION IN THE NITROSITE COMBUSTION METHOD FOR THE DIRECT DETERMINATION OF RUBBER4 By L. G. WESSON A N D E. S K N O R R
I n order t o make more feasible t h e possible use in technical laboratories of t h e nitrosite combustion for t h e direct determination of rubber in rubber goods, we have a t t e m p t e d t h e application of “combustion i n t h e wet way” t o this analytical procedure. T h e “nitrosite combustion” method, as described in a previous publication: is based upon t h e formation of t h e “nitrosite” of rubber b y t h e action of nitrogen oxide gases upon th.e caoutchouc of t h e sample. This is t h e n separated from other substances (fiilers), a n d Willstiitter and Stoll, “Untersuchungen iiber Chlorophyll,” p. 241. 2 J . B i d Chem.. 17 (1914), 190-249 8 Evidence in court. 1915. 4 This article represents thesis work done b y E. S. Knorr in the course for t h e degree of Bachelor of Science in Chemistry from t h e Case School of Applied Science. Read at t h e 53rd Meeting of the American Chemical Society, New York City, September 25-30, 1916. 6 L. G . Wesson, THISJ O U R N A L , 6 (1914), 459. 1
I39
burned in a specially constructed electrically heated combustion tube. T h e special apparatus a n d technique required was a decided obstacle t o t h e general use of this method, even should its reliability be demonstrated, a n d we therefore turned t o “wet combustion” as a n escape from this difficulty. I n t h e course of our experiments, acetone-extracted crude rubber was first used. T h e nitrosite was formed in t h e flask used for t h e combustion, a n d after t h e complete expulsion of t h e rubber solvent (chloroform), t h e combustion followed in a manner quite similar t o those later described. We obtained as dependable values 96.8, 97.0, 97.6, a n d 97.1 per cent C10H16, average 97.1 per c e n t ; theoretical, 97.3 per cent C I O H ~ G . I n t h e regular analytical procedure this simple t r e a t m e n t of t h e nitrosite is not possible since t h e latter must be separated from t h e mineral matter a n d other impurities b y t h e use of some solvent after filtration from t h e chloroform. We first used a solvent acetone, which was added t o t h e d r y nitrosite i n t h e combustion flask. T h e acetone was first evaporated off, t h e n t h e flask was heated I ~ / Z hrs. b y a boiling water b a t h while a current of dry air passed slowly through t h e flask. T h e value now obtained (100.7 per cent) upon combustion, indicated a retention of acetone. A repetition of this experiment with t h e use of only ethyl acetate as solvent gave 96.4, 97.1, a n d 97.0 per cent CloHiG. These figures were more promising. Moreover, t h e ethyl acetate on evaporation left t h e residual nitrosite in a more porous, a n d t h u s more favorable, condition for rapid expulsion of t h e organic solvent t h a n did t h e acetone. E t h y l acetate was therefore adopted a s t h e solvent i n all of t h e analyses of vulcanized rubber. T h e use of acetic ester did not, however, eliminate our troubles with retained solvent, as we found when we next turned t o t h e analysis of compounded rubber samples, instead of t h e raw gum. We believe t h a t this difficulty explains most of t h e erratic results we h a d t o t h e end of our work. We believe t h a t we have now found t h e remedy for this retention of solvent in t h e addition of water, containing a drop of hydrochloric acid, t o t h e nitrosite, a n d subsequent evaporation of this t o dryness, after all solvent has been removed i n t h e ordinary way. I n a sample’ compounded with 35.0 per cent Fine P a r a , using t h e method described, we found 34.7, 34.9, 34.8, a n d 34.2 per cent C10H16, average 34.7 per cent; theoretical, 34.4 per cent C ~ O H ~ G . I n a sample’ compounded with 40.0 per cent plantation rubber, we found 38.9, 39.8, 37.9, 38.1, a n d 37.7 per cent C10HI6, average 38. j per cent; theoretical value, 38.3 per cent CioHi~. PROCEDURE PREPARATION
OF
THE
NITROSITE
FOR
THE
COY-
BusTIoN-After t h e rubber sample has been ground g. in a meat chopper t o pass a 2 0 mesh sieve, a n d of i t extracted 3 hrs. with acetone a n d ‘ / 2 hr. or longer with chloroform, t h e extracted sample is allowed 1
Theee samples were kindly sent us b y the Bureau of Standards
