occur the residue acts as a n absorbent for silicone, causing lo^ results. After all the n-ater is removed and a taffy-like stage is reached, the benzene containing the silicone portion of the antifoam emulsion is decanted from the residue to a n evaporating dish with filtering to remove solid materials if necessary. The flask and filter are washed three times with fresh benzene and the total benzene extract and n-ashings are combined. The benzene is removed by heating in a hood on a n electric hot plate or steam bath. The residue is dried a t 100' C. for 1 hour and then dissolved with carbon disulfide and diluted to final volume. The snml:le in this stat'e is then submitted for a n infrared analysis. Infrared Determination of Dimethylpslysiloxane. -4portion of the carbon disulfide extract of thc residue is transfcrred to a cell of 0.6-mnt. path h g t h . Thc instrument is d l o w ed t o scan t 11P n-a ve-le ng t h interval from 7 . 5 to 9 iiiicrons a t the normal spcetl setting of approximately 1 micron per mii!utt.. The ;\IezSi hand a t 7.95 microns is used for qiinnt,itative measurement of t'he silicone content. The base line (-i) technique is used for the determination of the absorbance of the band.
Table
1
2 3 4
5
6
II.
Silicone Recovery Study on Pineapple Juice
0.0 3.G 5.4
5.6 6.3 24.3
0.0 3.2 4.4
4.4 5.5
20.2
..
89 82 i9 87
83
Bread. waffles, hydrolyzed vegetable protein. and canned and frozen vegetables nere all examined. I n the biological field. the same general method was used to examine liver, spleen, and kidney of rabbits, animal blood, blood anticoagulant, human blood, human lung. and rabbit feed. I n all cases recovery data equaled or exceeded those obtained in the pineapple juice studies (Table 11). LITERATURE CITED
(1) D ~ K Corning Corp., DOT Corning Annlvtical Method S o . 1.1.6 11956). ( 2 ) Ibib.: So. 4.1.2 (1958). (3) Ibid., No. 4.3.4 (1959). ( 4 ) Heigl, J. J., Bell, h l . F., IVhite, J. V., :%KAL. CHEM. 19,293 (194i). ( 5i Kahler, H. L.. 1x0. ENG. CHEU., XKAL.ED.13,536 (1941). ( 6 ) NrHard. J . A , . Servais. P. C.. Clark. H. rl.,As 4~ CHEX 20, 325 (1948). ( 7 ) Pettj-. G I T , I h d , 28, 250 (1956). ~I
DISCUSSION
From the absorbance, per cent concentration of silicone in the solution can be calculated and this figure is related to the amount of silicone in the original sample. Many vegetable materials that had been processed with silicone antifoaming agents have been examined by this procedure or various modifications of it as the specific sample required. The follou ing materials have been examined by the extraction and infrared technique.
(8 Pozcfsky, A , Grenoble, 11 E., Diwu k. Cosmetzc Inrl 80, 752 (1957). 4 ' 9 Smith, A L RIcHnrd J. il , A N ~ L I
~
C"EM3 1 , l l i - f (1959)
RECEIVEDfor revien February 8. 1960. Accepted April 11. 1960. 11th Annual Pittsburgh Conference on hnalytical Chemittry and Applied Spectroscopy, IIarch 3, 1960.
Detection of Diphenylamine and Its Derivatives in Spot Test An a lysis FRITZ FEIGL and DAVID GOLDSTEIN laboraforio da Produck Mineral, Ministerio da Agriculfura, Rio de Janeiro, Brazil Translated by RALPH
E. OESPER,
University o f Cincinnafi
,The blue color produced by fusion with hydrated oxalic acid can b e used as a specific and sensitive test for diphenylamine and its derivatives. Carbazole derivatives also respond positively. Limits of identification have been determined for 15 compounds of these classes. Spot test analysis amounts are adequate.
A
and sensitive test for oxalic acid ( 4 ) is based on the formation of diphenylamine blue (Aniline Blue) n hen osalic acid is heated to 200" C. m-ith diphenylamine (melting point 83 " C.) : SPECIFIC
This reaction may also be employed for detecting diphenylamine in a sensitive manner. Furthermore, trials mith 25 compounds of this class shon-ed that, with the exception of dipicrylamine and nitrocarbazole derivatives of diphenylamine, they all, including carbazole, behave like the parent compound. Two groups should be distinguished among the derivatives of diphenylamine, according to M hether there is suhstitution in the benzene ring or in the imide group. illembers of the first group nith a n unoccupied para position may be expected to give a reaction analogous to that of diphenylamine. This is not to be excluded in the second group, but a preliminary splitting off of diphenylamine through pyrohydrolysis may also be taken into account. A cleavage of this kind can be accomplished by heating with hydrated oxalic acid, as in the region of 110" to 180" C. the water of hydration lost by the oxalic
acid acts as quasi-superheat>ed wat'er, which then brings about the requisite preliminary splitting off of diphenylamine. This is the reaction picture of a so-called pyrohydrolysis (Z), a type of reaction which has brought about analytically usable cleavages, including some n-hich cannot be accomplished by the wet method ( 5 ) . The assumption that a pyrohydrolytic splitting off of diphenylamine may precede the formation of dipheiiylamine blue, when X-substituted diphenylamine derivatives are fused with oxalic acid, is supported by the findings that fusion of 14''-acebyldiphenylamine or A--nitrosodiphenylamine with osalic acid a t 120' to 150" C. results in the splitting off of acetic or nitrous acids, respectively. These products are readily detected in the gas phase by acid-base indicator paper or with filter paper moistened with Griess reagent. The pyrohydrolyees underlying these cleavages, VOL. 32, NO. 7, JUNE 1960
e
861
+ +
H3CCOT\'(CJ&,)z HzO + CH3COOH (CsHs)?NH (1) O"(CBHs)?
+ HNOi Ht0 + (CEHS)Z" +
(2)
may likewise be brought about by heating the diphenylamine derivatives with the monohydrate of manganous sulfate, which gives off its water of hydration in the range 150" to 200°C. (1)and thus functions as the water donor. The formation of quinoidal blue dyestuffs by fusion with oxalic acid can be employed for the microdetection of diphenylamine and its derivatives. This test is far more reliable than the blue color produced by treating diphenylamine and its derivatives with concentrated sulfuric acid containing alkali nitrate (5). This color reaction fails with acetyldiphenylamine, as-diphenylurea, ethyl-S,N-diphenyl carbamate, and several derivatives of carbazole. I n contrast, these com-
pounds, even in micro amounts, yield blue or blue-green products when fused with oxalic acid. Procedure. A micro test tube is used. A little of the solid or the evaporation residue of a drop of the liquid solution is heated with several centigrams of hydrated oxalic acid in a glycerol bath preheated to 160' C. The temperature is raised t o 180" to 190' C. A positive response is indicated by the development of a blue color within several minutes. The test revealed the following in microgram amounts: diphenylamine (0.5), N-methyldiphenylamine (0.5), N-acetyldiphenylamine (2), phenyl-lnaphthylamine (15), as-diphenylurea (3), 4,4-diphenylsemicarbazole (3), ethyl-N,N-diphenyl carbamate (5), Nphenylanthranilic acid (5), N,N-diphenyl formamide (2.5), Ar,hr-diphenylbenzidine (5), tropaeolin 00 [sodium p - (2 - hydroxy - 1 - naphthy1azo)benzenesulfonate ] (5), 1,l-diphenylhydra-
zine chloride (1.2), carbazole (0.5), N ethyl-4-diethylaminocarbazole (l), A'toluylsulfonecarbazole (1.5), and Nethyl-4-aminocarbazole (1). A positive response was also obtained with: p-nitrosodiphenylamine, 4-methyldiphenylamine, diphenylamine-4-sulfonic acid and its barium salt, 4-hydroxydiphenylamine, and p-butoxydiphenylamine. LITERATURE CITED
( 1 ) Duval, C., "Inorganic Thermogravimetric Analysis," p. 189, Elsevier,
Amsterdam, 1953.
(2) Feigl, Fritz, Angew. Chem. 70, 166
(1958 ).
RECEIVED for review December 28, 1959. Accepted February 18, 1960.
Colorimetric Determination of Secondary Alcohols by Conversion to Ketones FRANK E. CRITCHFIELD and J. A. HUTCHINSON Development Department, Union Carbide Chemicals Co., Division o f Union Carbide Corp., South Charleston, W. Va.
,The colorimetric determination of secondary alcohols in the presence of primary alcohols is based upon the oxidation of the sample with acidic potassium dichromate to form ketones from secondary alcohols. The amount of ketone formed is determined by a 2,4-dinitrophenylhydrazine colorimetric method. Primary alcohols are oxidized by the dichromate reagent to acids and do not interfere. Reaction conditions are presented for the determination of 10 secondary alcohols. Data are presented for the determination of 0.04 to 2.6% 2-propanol in ethanol and 0.4 to 1.8% isopropanolamine in ethanolamine. The method i s also applicable to the determination of ketones in the presence of aldehydes.
T
HE DETERMISATION of low concentrations of secondary alcohols in the presence of primary alcohols is usually difficult. Of the several methods proposed for this determination (3, 5-7) most are applicable to macro concentrations only. The method described here is based upon the selective oxidation of secondary alcohols to ketones using acid
862
ANALYTICAL CHEMISTRY
potassium dichromate. The amount of ketone formed in the reaction is determined by a modification of existing colorimetric 2,4-dinitrophenylh~-drazine methods ( 8 , 4 ) . Therefore, this investigation was primarily concerned with combining the two procedures. DEVELOPMENT
OF
METHOD
Many variables were studied. Because acetone is the oxidation product of 2-propanol, these two compounds were used for all of the preliminary investigations. Dichromate Oxidation of Alcohols. The extent of oxidation of organic compounds with acidic potassium dichromate depends considerably upon the acid strength of the reagent. The reagent of Aguhlon ( I ) , which contains 1.5% potassium dichromate and is approximately 1 2 s in nitric acid, has been used as an oxidizing agent for organic compounds in this laboratory for several years. The reagent is selective in that it will oxidize many secondary alcohols to ketones, aldehydes to acids, and primary alcohols to acids, and will not oxidize carboxylic acids. These generalizations do not hold for many bifunctional compounds.
For example, 1,2-glycols are cleaved regardless of whether the hydroxyls are primary or secondary. Also, oxalic acid and glyoxal are oxidized to carbon dioxide. Because of its selectivity this system was initially chosen for oxidizing secondary alcohols to ketones. However, the Aguhlon reagent was not satisfactory because excess dichromate ion must be reduced before the 2,4-dinitrophenylhydrazine reaction. When a reducing agent is added t o accomplish this, some of the nitric acid is reduced to nitrite ion which decomposes to nitrous oxide in the acid medium. This causes an objectional liberation of a gas and requires excessive reducing agent to react with the potassium dichromate. For this reason sulfuric acid was substituted for nitric acid in the reagent. The normality of the acid x a s not changed appreciably. Reduction of Excess Dichromate Ion. T o determine the amount of ketone formed by the oxidation of a secondary alcohol, the excess potassium dichromate must be reduced. This is necessary because dichromate ion will oxidize 2,4-dinitrophenylhydrazine and methanol used as a solvent.
