INDUSTRIAL AND ENGINEERIKG CHEhIISTRY
8Q
VOL. 12, NO. 2
Gelation time Taries with viscosity or degree of bodying as well as with the temperature a t which the oil is bodied. Critical livering curves for both zinc oxide and peacock blue with bodied linseed oils were plotted, and these curves also appear to hold for bodied oiticica and fish oils.
Literature Cited (1) Brown, W. B., and Farmer, E. H., Biochem. J., 29, 631-9 (1935). (2) Gardner, H. -4.Jr., Paint Varnish Production
M g r . , KO. 6, 16, 18, 30 (1936). (3) Kappelmeier, C. P. A , , Fettchem. limschau. 42 146-52 (1935). (4) McKinney, R. S., and Jamieson, G. S., Oil &. SOUP,13, NO. 1. 10-11 (1936).
f5) \
viscosfTY-
Mattiello. J.. and Work. L. T.. Xatl. Paint. Varnish and Lacquer Assoc., Sci. Sect., Circ.
502 (March, 1936). (6) Morrell, R. S., and Davis, W. R., J . Oil Colour Chem. Assoc., 19, No. 195, 359-62 (1936). (7) Sorenson, S. O., Schumann, C. J., Sehumann, J. H . , and Mattiello, J., IKD.ESG.CHEW,30,
P O / S P S
FIGURE 4. LIVERING TENDENCIES OF OIL
the cases studied, was 2 2 . i Doises, and the time required to reach this viscosity at 6620 F: (350" c.)was minutes.
,
211-16 (1938).
(8) F o r k , L. T., Swan, C., Wasmuth, A., and Mattiello, J., Ibid., 28, 1022 (1936). PRESENTED before t h e Division of Paint and Varnish Chemistry a t the Y i t h Meeting of the American Chemiral Society, Baltimore, hld. ~
Determination of Pyrethrin I Linearity of Results by Mercury Reduction Method D. A. HOLADAI-
~ V J. D
J . T. GRAHA\I. Food and Drug Administration, Washington, D. C.
ILCOXON (4) proposed a method for the determination of pyrethrin I, based on the reduction of the mercuric sulfate in DenigPs reagent to the mercurous condition, followed by precipitation as mercurous chloride and titration with potassium iodate. That the reduction of the mercuric sulfate is nonlinear was implied by Wilcoxon when he specified limits of 50 to 70 mg. of pyrethrin I, between which his method should be used. Martin ( 3 ) pointed out that different sized aliquots of the same solution analyzed by Wilcoxon's procedure gave different percentages of pyrethrin I. Holaday ( 2 ) called attention to errors in the Kilcoxon method due to the presence of unsaturated organic compounds that titrate with the iodate solution along with the mercurous chloride. H e proposed a modification in which these unsaturated compounds were removed by washing with alcohol or acetone, followed by chloroform, and this modification has been adopted by the Association of Official Agricultural Chemists as a tentative method (1). The present investigation was undertaken to determine whether this modification was subject to the same nonlinearity. Pyrethrum extract, obtained by extracting the powdered flowers with petroleum ether and evaporating off the solvent, was used for the work. Twenty grams of this extract were dissolved in petroleum ether, the solution was filtered, the petroleum ether was evaporated, and the residue was saponified with alcoholic sodium hydroxide. The alcohol was removed by boiling and the aqueous solution was treated with barium chloride and filtered. Excess barium was precipitated in the filtrate with sulfuric acid, the barium sulfate was filtered off, and the clear filtrate was made slightly alkaline and diluted to 1 liter. From this stock solution aliquots were taken for analysis. Each
1 Pyrethrin I,ny.
FIGURE 1
/25
ANALYTICAL EDITION
FEBRUARY 15, 1940
TABLEI. RELATION BETWEEN VOLUMES OF SOLUTION PYRETHRIN I CONTENT Pyrethrin I Determined cc. Mg 3 20 5 5.9' 10 7.96 15 10.3b 20 13.9b 25 28.2b 50 43.l a 75 100 57,O" 125 71.0b 150 85.8b 114.2' 200 0 Analysis b y J. J. T. Graham. b Analysis by D. A. Holaday. Aliquot
.
Pvrethrin I dalculated Using 100-Cc. Aliquot a s Standard
.4ND
Difference from Standard
'KO.
MQ.
2.9 5.7 8.6 11.4 14.3 28.5 42.8 57.0 71.3 85.5 114.0
10.3 +0.2 -0.7 -1.1 -0.4 -0.3 f0.3 0.0
-0 3 +0.3 +o 2
81
within the range investigated the reduction is linear. The linearity of results obtained by this modification shows that the erroneous values obtained using the original Wilcoxon procedure are not due to compounds other than chrysanthemum monocarboxylic acid reacting to give mercurous sulfate. The interferences are no doubt due to unsaturated organic compounds which absorb iodine during the titration with potassium iodate. These compounds which are precipitated along with the calomel are removed from the precipitate by washing with alcohol or acetone, followed by chloroform. The linearity of the results obtained indicates that the reduction of the Denigss reagent is a clear-cut reaction which is not affected by the quantity of chrysanthemum monocarboxylic acid within the limits of the experiment.
I
aliquot was acidified and analyzed by the Holaday ( 2 ) modification of Wilcoxon's method, except that alcohol was used instead of acetone, The three largest aliquots were extracted three times with petroleum ether, and 15 cc. of Denighs reagent were used in the reduction. The results are given in Table I. The determined pyrethrin content of each aliquot plotted against the volume of the aliquot (Figure 1) shows that
Literature Cited (1) Assoc. Official Agr. Chem., J . Assoc. OficiuZ A g r . Chem., 21, 78 (1938). (2) Holaday, D. A., ISD.ESG.CHEW,Anal. Ed., 10,5 (1938). (3) Martin, J. T., J . Agr. Sci., 28,Part 111, 456-71 (1938). (4) Wilcoxon, Frank, Contrib. Boyce Thompson Inst., 8, No. 3, 176-81 (1936).
Analvsis of Rubber for Certain Diarylamine J
d
and Ketone-Diarylarnine Antioxidants L. H. HOWLAXD
AND
E. J. HART, United States Rubber Company, Passaic,
The technique of semiquantitative anti'oxidant analysis which employs a turpentine oxidation method is described and the results of characteristic analyses are given. The antioxidant effect of BLE (a ketone-diarylamine reaction product) in purified turpentine as measured by the induction period is proportional to the BLE concentration whether added to the turpentine directly or as one of the components of an acetone extract of a rubber mixture. Certain qualitative tests are also given for the detection of antioxidants in a tire tread vulcanizate.
T
HE purpose of this paper is to present methods for the
detection and semiquantitative determination of certain types of antioxidants and anticracking agents in rubber articles. The specific compounds reported on are a ketonediarylamine reaction product (BLE), a ketone-diarylamine modification (BXA), N,N'-diphenyl-p-phenylene diamine (DPPDA) , and dimethylacridan (hereafter referred to as DMA) , but the semiquantitative method developed may be used for the determination of other antioxidants. During the past few years a number of methods have been published by Endoh (2-6) and Shimada (6) on the qualitative detection of antioxidants by color tests. These authors have described a number of color reactions characteristic of commercial antioxidants. These are very useful if the chemical can be isolated from the rubber and then tested. Craig (1) has described a semiquantitative method for the isolation and determination of diarylamine antioxidants by
N. J.
steam distillation from thinly sheeted rubber compounds. I n this method, 30 to 40 grams of' the unvulcanized or vulcanized rubber stock are treated wit,h steam a t 170" to 180' C. for 2.5 to 3 hours and the amine antioxidants isolated from the distillate. The recovery of amine was above 90 per cent for pure gum compounds, and as low as 16 per cent for tread compounds containing 0.5 part of N ,N'-diphenyl-p-phenylenediamine. The semiquantitative method given below for the analysis of BLE, BXA, DPPDA, and DRIA follows, in principle, the one described by Stern and PuFfett ('7) who measured the increase in weight and also the volume of oxygen absorbed by linseed oil containing rubber antioxidants as a function of time. I n these experiments Seoaone appeared to give induction periods proportional to its concentration in the linseed oil. When making semiquantitative antioxidant analyses by the procedure described in this paper, it is sometimes necessary to determine qualitatively what antioxidants are present in the rubber. A qualitative method that functions satisfactorily for the antioxidants under discussion is a color test based on an oxidation procedure. For the detection of the antioxidant present in a rubber stock, about 1 gram of the stock is cut into 2-mm. cubes and gently refluxed with 2 cc. of concentrated acetic acid for 2 minutes. After cooling, the acetic acid solution is decanted, 1 drop of concentrated sulfuric acid is added, and after mixing 2 drops of 30 per cent hydrogen peroxide are added. The colors developed are given in Table I. Experiments have shown that the oxidation of certain unsaturated compounds, such as rubber and turpentine, is autocatalytic in nature and very susceptible to the action of certain added inhibiting ingredients. I n general, antioxidants for rubber are also antioxidants for turpentine, and on this fact is based a method for their semiquantitative de-
