V O L U M E 26, NO. 10, O C T O B E R 1 9 5 4 Table I1 (bottom) gives the results obtained on Bureau of Standards cast irons using the catalyst hlonolyzer bulb in the system. The iodometric sulfur-gravimetric carbon method Ivas Equivalent results were obtained with the acidimetric sulfur-gravimetric carbon method.
1661 (7)
Holler, A. C., and Klinkenberg, R., ANAL. CHEM.,23,
(8) Holler, A. C., and Yeager, J. P., F o u n d r y , 72, 83 (1944). (9) Holthaus, c., 2. a ' W W . C'hem., 389 330 (1925). (10) Lindberg Engineering Co., Chicago, Ill., "Instructions for Installation and Ooeration of Lindbere Hieh Freauencv - ComI
LITERATURE CITED
Aites, 'Ar.K., Steel, 125,92 (Dec. 12, 1949). Am. Soc. Testing Materials, "hlethod of Chemical -1nalysis .Metals," p. 129, 1950. Boedanchenko. A. G.. Zaaodskava Lab. 6 . 369 (.1 9 3 3 . ~
~ - - ~ ~
.
~
1696
(1951).
(11) (12) (13)
-
bustion Furnace LI-500-.\." 1950. Misson, G., C h i m i e & I n d u s t r i e , Spec. No. 326 (March 1932). U. S. Steel Corp., "Sampling and Analysis of Carbon and Alloy Steels," p. 309, Reinhold Publishing Corp., New York, 1938. Zaffuto, G., Acti. X congr. intern. chim., 3, 487 (1939).
I
Ibid., 12,119 (i946)-. Burns, B., and Braude, G., Zhur. A n a l . K h i m , 4, 31B (1949). Gerke, F. K., and Kardakova, Z. I., Zavodskaya Lab.. 3, 9 i 7 (1934).
RECEIVED for review Dewniber 28,
1954. Accepted J u n e 28, 1954. Prcsented before the Pittsburgh Confprpnce on hnalytical Chemistry a n d Applied Spectroscopy. J l a r c h 1953.
Ultraviolet Absorption Spectra of the Hydrolysis Products of Diethyl Barbituric Acid G. R. JACKSON, JR., J. R. WESCHLER, and R. L. DANNLEY Department o f Chemistry, Western Reserve University, Cleveland, Ohio
The ultraviolet absorption spectra of the various hydrolysis ,products of diethyl barbituric acid are given.
I
N T H E course of an investigation of the effect of p H and temperature upon the hydrolysis of diethyl barbituric acid (barbital), the ultraviolet spectra of the possible hydrolysis products were determined t o ascertain whether these products interfere uith the quantitative determination of barbital b y the spectrophotometric method of Goldbauni ( 4 ) . EXPERIMENTAL
a-Ethyl butyramide was prepared in 60% yield by adding, drop by drop, 10 grams of a-ethylbutyrylchloride(EastmanWh1te Label) to 5 ml. of concentrated ammonium hydroxide which was cooled in a salt-ice bath. The addition of the acid chloride was regulated so that none of the mist of ammonium chloride escaped from the flask. After shnding 48 hours, the white solid which formed was removed by filtration, washed with water, and recrystallized from an ethyl alcohol-water mixture; white needles, melting point 102' to 105' C.; literature melting point, 105" C. ( 3 ) . a-Ethylbutyric Acid (Eastman White Label) was redistilled and the fraction boiling at 193" t o 194' C. was collected. Urea (hlerck reagent grade) was recrystallized from hot alcohol; melting point, 132' to 133' C. Diethyl Malonic Acid. .4 mixture of 25 grams of diethyl diethyl malonate (Eastman White Label), 25 grams of potassium hydroxide, 40 ml. of water, and 25 ml. of ethyl alcohol was refluxed for 20 hours. The solution was washed with ether to remove unchanged ester, made acid to Congo red, and extracted with ether. The ether extract was washed with water and then dried over anhydrous sodium sulfate. The ether was evaporated and the residue was cooled in ice. h white solid formed which was washed with ligroin, filtered, and recrystallized from chloroform; 4 0 3 yield, melting point, 126" C.; literature melting point, 125 to 127" C. ( 1 ) . a-Ethylbutyrylurea, prepared according to the procedure of Stoughton (j),had a melting point of 207' (literature melting point, 207") when recrystallized from an ethyl alcohol-water mixture. Diethyl malonuric acid, prepared according to the procedure of Fischer and Dilthey (Z), had a melting point of 162" C. (literature melting point, 162') when recrystallized from warm water . PROCEDURE FQR ULTRAVIOLET SPECTRA DETERMINATION
The same general method w&s used in making up the solutions of urea, a-ethylbutyric acid, a-ethylbutyramide, and diethyl
malonic acid. The amount of material calculated to be given upon complete hydrolysis of 0.5 gram of barbital to that product, was weighed out and diluted to 100 ml. with cold water. Two 1-ml. samples were pipetted and diluted to 50 ml., one with 0.45A' sodium hydroxide and the other with a borate-sodium hydroxide buffer of pH 10.3. Because of the insolubilitv of a-ethvlbutvrvlurea and diethvl malonuric acid in water, so1;tions !veri preparkd and the concehtrations determined as follows. -4 saturated solution of the compound was prepared by stirring 0.5 gram of the compound in 100 ml. of water for 0.5 hour. The resulting mixture was then filtered and the samples werc pipetted from the filtrate and diluted in the same manner as above. In addition another 1-ml. sample was taken, placed in a weighed evaporating dish, covered, allowed to evaporate, and weighed to determine the weight of compound in 1 ml. of solution. The solubility of a-ethylbutyrylurea was 0.0006 gram per ml. and that of diethyl malonuric acid was 0.0016 gram per ml. The ultraviolet absorption spectra of the compounds were determined on a Beckman Nodel DU spectrophotometer. RESULTS
The ultraviolet spectra of the various hydrolysis products show that all of the products give an optical density not over 0.03 unit except a-ethylbutyrylurea and diethyl malonuric acid. The latter products show considerable absorption a t the shorter wave lengths in very alkaline solution (0.45.V sodium hydroxide). However, a t 260 mp, the wave length a t which the concentration of barbital is determined in Goldbaum's method ( 4 ) , the ahsorp-
Table I.
h
230 235 240 245 250 255 260 2G5 270 275 280 285 290 295 300
Absorbances of a-Ethylbutyrylurea (12 y per M I . ) and Diethyl Malonuric Acid (32 y per Ml.) =-Et h ylbu t yrylii rea. PH 0.45-4' 10.3 NaOH
0.008 0,006 0.006
0.266 0.185 0.108 o.oci0 0.035 0.026 0.022 0.021 0.019 0.018 0,019 0,019
0.006 0.006
0,019 0.019 0,019
0.023 0.019 0,015 0.008 0.006 0.006 0.006
0.006
O.OOR
O.OOG
Diethyl Malonuric Acid 0.45.v PH XaOH 10.3 0.074 0.858 0.680 0.066 0.474 0.057 0.2R2 0.044 0.031 0.173 0.023 0.108 0.071 0,018 0,056 0.015 0.046 0.014 0.014 0.041 0,039 0.014 0.036 0.014 0.034 0.012 0.010 0.030 0 028 0.010
A N A L Y T I C A L CHEMISTRY
1662
tion is small. If a solution of barbital containing 15 y per ml. (final concentration after dilution according to Goldbaum's method) has been completely hydrolyzed t o the eethylbutyrylurea, the absorption would indicate the presence of 3% of the original weight of barbital. Likewise, if the barbital were completely bydrolyBed to diethyl malonuric acid the absorption would indicate the presence of 6% of the original weight of barbital. The results obtained indicate that the method for determining. barbital concentration may be used for following the rate of hydrolysis of barbital provided that a 5% accuracy is satisfactory.
ACKNOWLEDGMENT
The authors express their appreciation to the Research C o p . for the grant which made this research poasihle. LITERATURE CITED
(1) Daimler. C.,Ann.. 249, 181 (1888). (2) Fisoher. E., m d Diltheu, H., Ibid., 335, 362 (1904). (3) Freund. M.,and Herrrnan, P.,Ber., 23, 189 (1890). . , 1604 (1952).
