V O L U M E 2 2 , NO. 10, O C T O B E R 1 9 5 0 .4pparently compounds that react readily with hydrogen chloride prevent the normal color reaction. -4bsorption spectra of the reactions of activated GDH with vitamin A when solvent to reagent ratios of 1:0, 1:5, l : , l , 5:1, and 9 : 1 were employed are presented. The extinction coefficients a t 555 mp were essentially the same in the cases of the 1 : 3, 1 :7, 1 :5, and 1: 3 ratios. As the ratios were increased above 1:3, the absorption a t 555 mp decreased while the absorption a t 337, 353, 372,395, and 422 mp increased and reached maximum values when a 9 : 1 ratio was used. These maxima in and near the ultraviolet resemble to some extent the type absorption spectrum of anhvdro vitamin .4. ACKNOWLEDGMENT
The kindness of F. H. Spedding in making the Cary recording spectrophotometer available is acknowledged. LITERATURE CITED (1) &allen,R. S., Wise, G . H.. 688 (1949).
and Jacobson, N. L., J . Dairy Sci., 32,
(2) Braekkan, 0. R., ANAL.CHEM., 21, 1530 (1949). (3) Chilcote, M.E., Guerrant, X. B.; and Ellenberger, H. A.. Zbid.. 21, 1180 (1949).
1295 Edisbury, J. R., Gillam, A. E., Heilbron, I. AT., and Morton. R. A., Biochem. J . , 26, 1164 (1932). Feinstein. L., J . Bid. Chem., 159, 569 (1945). Hanse, A. R., Conger, T. TV.,Wise, E. C., and Weisblat, D. I., J . A m . Chem. SOC.,70,1253 (1948).
Kelley, B., and Day, H. G., J . Sutrition, 40, 159 (1950). Murley, W. R., Jacobson, S . L., Wise, G. H., and Allen, R. S., J . Dairy Sei., 32, 609 (1949).
Penketh, D. D., Nature, 161,893 (1948). Shantz, E. hl., Cawley, J. D., and Embree, N. D., J . Am. Cheiu. Soc., 65, 901 (1943).
Sobel, -4. E., and Rosenberg, A. A.,
h . 4 ~ . CHEM..21, 1540 (1949). Sobel, .4. E., Sherman, M., Lichtblau, J., Snow, S., and Kramer, B., J . Nutrition, 35, 225 (1948). Sobel, -4. E., and Snow, S. D., J . B i d . Chem., 171,617 (1947). Sobel, .4.E., and Werbin, H., Ax.4~.CHEM.,19, 107 (1947). Sobel, A. E., and Werbin, H., IND.ENG.CHEM.,ANAL.ED., 18, 570 (1946). Sobel, 4 . E., and Werbin, H., J. B i d . Chem., 159, 681 (1945). Squibb, R. L., Cannon, C. Y., and Allen, R. S., J . Dairy Sci., 31, 421 (1948). Zbid,, 32, 565 (1949). Wall, M. E., and Kelley, E. G., ANAL.CHEY.,20, 757 (1948). Yang, S.P., M.S. thesis, Iowa State College, 1949.
RECEIVED March 9, 1950. From a thesis submitted by R. 9. Allen to the Graduate School of Iowa State College for the Ph.D. degree. Journal Paper N o . 5-1761, Iowa Agricultural Experiment Station, Project 814, Ames, Iowa.
Quantitative Analysis of Mixtures of Primary, Secondary, and Tertiary Aromatic Amines SIDNEY SIGGIA, J. GORDON " N A Y AND IRENE R. KERVENSKI Genera1,Aniline & Film Corporation, Easton, Pa. A method has been devised for determining primary, secondary, and tertiary aromatic amines in the presence of each other. The final analyses are acidimetric in nature; however, the sample is first altered in various ways to make the determination of each component possible.
T
HE quantitative analysis of hivtures of amines has been a problem for many years. Wagner, Brown, and Peters ( 5 ) devised a system for determination of primary, seeondary, and tertiary aliphatic amines, but this system could not be applied to aromatic mixtures because of the much weaker basic properties of the aromatic amines. The methods described below utilize the same reactions as those devised by Wagner, Brown, and Peters, but the reaction media and techniques used make possible the utilization of the analysis system for the determination of aromatic amine mixtures. This method is also readily applicable to aliphatic amine systems, but the aliphatic systems are adequately covered by Wagner, Brown, and Peters. RIitchell, Haa kins, and Smith (2) proposed determining tertiary amines by determining first the sum of primary and secondary amines by acetylation, measuring the excess anhydride by aquametric means; the tertiary amine was obtained by determining total base and subtracting the sum of primary and secondary amines. I n aromatic systems the amines involved are so weakly basic that titration of total base for determination of tertiary amines is impossible by ordinary means. Also, the acetylation procedure used for determining primary plus secondary amines cannot be used when alcohols are present with the amines. The procedure has an unnecessary step in the addition of excess water and determination of the water by the Karl Fischer reaction. Simply determining the excess anhydride after acetylation by titration with sodium hydroxide has been found to yield very good results.
Hawkins, Smith, and Mitchell ( 1 ) also devised a procedure for determining primary amines in the presence of secondary and tertiary amines. The sample is reacted with benzaldehyde and the water liberated is determined by the Karl Fischer reaction. This procedure involves the use of hydrogen cyanide, which necessitates special handling and is more time-consuming than the me'thod described below. In the method for determining aromatic amine mixtures which is described in this paper the tertiary amine is determined by adding acetic anhydride directly to a weighed sample. After a short time the acetylated mixture is dissolved in 1 to 1 ethylene glycol-isopropyl alcohol, and the tertiary amine (which is not affected by the anhydride) can be titrated using standard hydrochloric acid. The glycol-isopropyl alcohol solvent is used to accentuate the titration of the tertiary amine, which is a weak base. I t was first proposed by Palit ( 4 ) to make possible the titration of weak bases that could not be accurately determined by titration in aqueous solution. The primary aromatic amine in the mixture is determined by titrating the total base in the sample in the 1 to 1 ethylene glycolisopropyl alcohol solvent. To a separate sample salicylaldehyde is added to remove the primary amine via the Schiff reaction, and the remaining base in the sample is then titrated. The difference between the two titrations will yield the primary amine content. The secondary amine content is determined by taking the titration value after addition of salicylaldehyde: tertiary amine
ANALYTICAL CHEMISTRY
1296
plus secondary amine. B!. suhtracting the valuc ol)tained for the tertiary amine as descrilietl ahove, the amount of secondary :imine ?:in Le determined.
111 of HC1 X -Y grams of sample X 1000 moles of tertiary amines per gram of sample
Calculations. P m m w AMINE REAGENTS
Ethylene glycol-isopropj.1 alcohol mixture, 1 to 1. Standard 1 .\- hydrochloric acid in ethylene glycol-isopropyl alcohol mixture, 06 ml. of concentrated hydrochloric acid diluted to 1 liter with 1 to 1 ethylene glycol-isopropyl alcohol. C.P. scctic anhydride. S:ilicylalclehyde (from liiwlfite aGdition compound). PROCEDURES
Procedure A. Total Amines. A sample containing approxiniatelv 0.02 mole of total amines is accurately weighed in a iveighhg bottle. The contents of the weighing bottle are washed into a 150-ml. beaker with 1 to 1 ethylene glycol-isopropyl alcohol mixture and ethylene glycol-isopropyl alcohol mixture is added until the volume is approximately 50 ml. A p H meter is used to indicate the apparent pH after each addition of acid, as the sample is titrated with 1 -V hydrochloric acid prepared in the ethylene glycol-isopropyl alcohol mixture. The neutralization point is determined by plotting the apparent pH against milliliters of acid. 111.of HC1 X S grams of sample X 1000 moles of total amines per gram of sample
Procedure B. Secondary plus Tertiary Amines. A sample containing approximately 0.02 mole total of secondary and tertiary amines is accurately weighed in a weighing bottle. The contents of the weighing bottle are washed into a 150-ml. beaker with 1 to 1 ethylene glycol-isopropyl alcohol mixture, and ethylene glycol-isopropyl alcohol mixture is added until the volume is approximately 50 ml. Five milliliters of salicylaldehyde are added (more if the amount of primary amine is larger than 0.035 niole). T h r mixture is stirred thoroughly and allowed to stand at room temperature for 0.5 hour. A pH meter is used toindicate the apparent pH after each addition of acid as the sample is titrated with l -Yhydrochloric acid prepared in the ethylene glycolisopropyl alcohol mixture. The neutralization point is determined by plotting apparent pII against milliliters of acid.
JII. of HCI X S grams of sample x 1000 moles of secondary plus tertiary amine per gram of sample Procedure C. Tertiary Amines. A sample which contains approximately 0.02 mole of tertiary amine is accurately weighed in a 20 x 150 mm. test tube and cooled by placing in a beaker of ice. Ten milliliters of acetic anhydride are added slowly while the test tube is swirled. The test tube, and cont,ents are allowed to stand 15 minutes a t room temperature. The contents are quantitatively transferred from the test tube into a 150-ml. beaker by washing with 1 to 1 ethylene glycol-isopropyl alcohol mixture. Ethylene glycol-isopropyl alcohol mixture is added until the volume is approximately 50 ml. A pH meter is used to indicate the apparent pH after each addition of acid as the sample is titrated with l ;\-hydrochloric acid prepared in the ethylene glycolisopropyl alcohol mixture. The neutralization point is determined by plotting the apparent p H against milliliters of acid.
Table 1.
Determination of Primary, Secondary, and Tertiary Amines
Primary, % System Calcd. Found Aniline, ethylaniline, 3 3 . 2 9 3 3 . 0 5 and diethylaniline 74.9.3 7 5 . 4 1 9.70
10.52
Aniline, methylaniline. 3 3 . 3 9 3 2 . 8 6 and dimethylaniline 7 4 . 9 7 7 4 . 5 7 9.77
10.43
Secondary, % Calcd. Found
Tertiary, % Calcd. Found
31.89 12.02 43.30 33.34 12,50 45.13 32.96 45.07
34.79 13.02 47.00 33.24 12.58 45.05
31.87 11.29 42.04 32 61 12.44 45.27 33.78 44.53
I-Saphthylamine, 34.16 33.34 ethyl-I-naphthyl9 . 8 9 10.14 amine. and diethyl1-naphthylamine 1-Naphthylamine, and 4 9 . 9 6 4 9 . 3 8 .. dimethyl-1-nayh18.17 18.92 a ... t tiylamine a Secondary amines of this system could not be obtained.
.
34.90 12.96 47.32 34.00 12.52 45.42
32.88 32.50 45.04 44.74 46.44 75.94
46.59 76.21
+
Moles of total amine - moles of sec. tert. amine gram gram moles of Drimarv amine gram Noles of primary amine X mol. wt. of primary amine X 100 = gram % primary amine SECOXD.4RY
,4>1I?JE
Moles of see. amine gram
+ tert. amine - moles of tert. amine -,
gram moles of sec. amine gram
Moles of see. amine X mol. wt. of sec. amine X 100 = gram % see. amine I
TERTIARY .%MITE IIoles of tert. amine X mol. wt. of tert. amine X 100 = gram % tert. amine D1 SCUS SION
One of the desirable features of this system of analysis is the small number of interferences. First of all, an interference has to be basic. In the determination of tertiary amines, any basic impurity is neutralized by the acetic anhydride and is thus removed. In the primary amine determination, it is the decrease in basicity on addition of salicylaldehyde that is measured. Any basic impurity is figured in both titrations and does not affect the difference. A basic impurity will affect only the determination of the secondary amine. However, if the alkaline impurity is strong enough, it can be determined by a differential titration in the presence of the aromatic amines, which are very weak bases. The secondary amine value can then be corrected. Ammonia present in mixtures of aniline and monoethyl and diethylaniline was handled very satisfactorily by the above technique. It was found impossible to determine N,iV-di-(P-hydroxyethy1)aniline by the tertiary amine procedure. On acetylation, the hydroxyl groups on the molecule were esterified, and this resulted in such a decrease in the basicity of the compound that it was no longer titratable even in the special solvent mixture. Systems containing diphenylamine and triphenylamine could not be determined because these materials are too weakly basic to be titrated. In the determination of secondary plus tertiary amines, the buffering action of the Schiff base formed after the reaction with salicylaldehyde is sometimes strong enough to decrease the sensitivity of the titration curve. I n these cases, it is advisable to make the plotted curve more sensitive by extending the pH scale of the graph over a longer length, so that each division on the graph equals a smaller gH unit. I n this way, the break in the curve is accentuated, and a more accurate reading is made possible. The above procedures provide an easily applicable way of determining primary, secondary, and tertiary amines when all are present in the same sample. Combinations of the above procedures can also be applied to determine mixtures when only two of the three types of amines are present. However, in the letter case, other techniques can sometimes be used which give the analysis for the two components more directly, more accurately, or faster.
1297
V O L U M E 22, NO. 10, O C T O B E R 1 9 5 0 The procedure for tertiary amines described above is the most efficient for these compounds in the presence of primary or secondary amines. The procedure for primary amines as described above is the only known method for determining these compounds in the presence of secondary amines. However, if the mixture to be analyzed consists of a primary and tertiary amine, the primary amine is best determined by the acetylation procedure of Ogg, Porter, and Willits (S), which is faster than the salicylaldehyde method. Alcohols interfere with the acetylation method. The acetylation method is also the best way of determining secondary amines in the presence of tertiary amines; it is more
direct than determining total amines and su1itr:ictiiig the tertiary amine. LITERATURE CITED
(1)
Hawkins, W.,Smith, D. M., and ?&tchell, J., Jr., J . A m . Chrm. Soc., 66, 1062 (1944).
(2) Mitchell, J., Jr., Hawkins,
IT.,and Smith, D. 31..Ibid., 66, 782
(1944). (3) Ogg, C. L.,
Porter, IT. L., and Willits, C. O., ISD. Esc. CHEY., ED..17. 397 (1945). (4) Palit, S., Ibid., 18, 246-51 (1946). (5) Wagner, C. D., Brown, R. H., and Peters, E. D., J . A m . Chein. ;~B.AL.
Soc., 69,2609-14 (194T).
R E C E I V E.Lori1 D Z!, 1950.
Direct Determination of Oxygen in Compounds Containing Carbon, Hydrogen, and Oxygen A Physical-Chemical Technique CHARLES C. HARRIS, DONALD & SMITH, I. A N D JOHN MITCHELL, J R . Polychemicals Department, E. I. du Pont de Nemours & Company, Inc., Wilmington, Del.
A new technique is presented for the direct determination of oxygen in organic compounds, based on the Unterzaucher carbon-reduction procedure. The sample is decomposed in a stream of helium and the pyrolysis products are circulated in a closed system over carbon a t 1100" to 1150' C. until conversion of all the oxygen to carbon monoxide is complete. During circulation, essentially all the hydrogen is removed selectively by diffusion through a heated palladium tube. This procedure permits the use of very large samples, which is of particular value in the analysis of materials of low oxygen content. Using a thermal conductivity bridge, the composition of the resultant helium-carbon monoxide mixture is determined with a sensitivity of 0.209'0 carbon monoxide per mv. The amount of carbon monoxide formed from the oxygen in the sample may be calculated after measurement of the total volume of gas. Because the thermal conductivity measurements are referred to a control cell, tank helium may be used without further purification. By employing continuous recording of bridge potential, a valuable means is provided for following the course of pyrolysis and conversion., Preliminary results on a wide variety of solid and liquid compounds indicate a relative accuracy of 1% or better.
P R U L Y general procedure is not yet available for the direct determination of oxygen in organic compounds. ;1survey of the methods in the literature (1, 2, 4, 7 , 10, 12) leads to the conclusion that the technique of Gnterzaucher (12) is the one most likely to provide the basis for such a procedure. Unterzaucher's technique was based on the decomposition of the sample in a carrier of nitrogen gas and conversion of the products to carbon monoxide and hydrogen by passage over amorphous carbon a t 1100" C. The carbon monoxide was determined by reaction with iodine pentoside followed by titration of the liberated iodine. The aurhors' experience with this method paralleled that of Aluise, Hall, Staats, and Becker (1) in that high variable blanks and irregular behavior for a large number of compounds were found. The excellent paper published by these authors in 1917 described a procedure in which many of the objections to Cnterzaucher's original method (12) were overcome. Recently Dinerstein and Klipp ( 3 )showed that the technique of Aluise and his co-Tvorkers could be extended to the analysis of compounds containing as little as 0.1~57~ oxygen. At these low oxygen contents, the blank may be equivalent to nearly 5070 of the total oxygen found. The magnitude of this blank thus may be considered to set the lower limit of the method.
Kalton, McCulloch, and Smith (13) described a sensitive method for oxygen contents in the range of 0.01 to 6%. Their technique, which also was based on reduction over carbon, employed helium as the carrier gas and used a colorimetric gel for measurement of carbon monoxide. Commenting on the results of unpublished work a t the Sational Bureau of Standards, Walton, McCulloch, and Smith suggested that the blanks previously found in applications of the Unterzaucher technique could be attributed to the iodine pentoside reagent. These authors stated that in their method the blank was reduced to an amount equivnlent to O . O O l ~ ooxygen in a sample. In reporting their resultq, Walton and co-workers indicated a relative accuracy of 2 to
5 %. In the technique described in the present paper, the sample is pyrolyzed in a stream of helium, and the decomposition product? are circulated in a closed system over carbon a t 1100" C. During circulation, hydrogen is removed selectivelv by diffusion through a heated palladium membrane, and the rate of formation of carbon monoxide is follo~wdby recording the change in thermal conductivity of the gas mixture. When conversion and hydrogen removal are complete, as indicated by no further chanqe in bridge potential, the total volume of gaj i q measured
