V O L U M E 23, NO. 3, M A R C H 1 9 5 1
541 Ultraviolet Absorption Method. Ethyl alcohol wm used a5 the solvent and absorption measurements were made with a Beckman quartz spectrophotometer. The maximum absorption for benzil in 95% ethyl alcohol occurs a t a wave length of about 260 mp (6). Absorption readings were made a t 260 mp and a slit width of 0.5 mm. The Beer-Lambert law holds only approximately for benzil in 95% ethyl alcohol a t this wave length. For this reason it was necessary to plot a curve of log Io/I versus concentration. The cloth samples were extracted Tith 95’% ethyl alcohol and readings were made on concentrations in the range of 0.003 to 0.015 gram per litrr.
Table 11. Fluorometric Determination of Benzil i n Cloth Containing Various Impregnating Agents Additive Impregnated in 2.5 G. Cloth Sample Agent Weight, g. Sizing Cnknown rnknown Sizing h-m-eonsl -~ -~ 0 05 Naeeonal 0 05 0 05 Span 80 Span 80 0 05 Chlorinated paraffin 0 125 0 125 Chlorinated paraffin 0 013 Polyvinyl alcohol Polyvinyl alcohol 0 013 ~
~~
Benzil Added t o Sample, 1Ig.
0 025 0 025 0 025 0 025 0 025 0 025 0 02.5 0 025 0 025 0 025
Benzil Found, xg. 0 024 0 024 0 023 0 024 0 025 0 024 0 025 0 024 0 021 0 016
DISCUSSION
hlarked changes in the fluorescence of solutions containing the fluorescent compound took place with large changes of pH. Solutions made alkaline with ammonium or potassium hydrovide showed a great decrease in fluorescence. However, under the conditions of the procedure outlined above, only a slight effect due to small amounts of acidity in the alcohol was noted. Neutralization of the alcohol eliminated this difficulty. In all applications of the fluorometric method described hcre, a straight-line curve of Klett photofluorometer readings against milligrams of benzil in concentrations up t o 0.03 mg. per ml. was obtained.
benzil concentration, using known solutions treated as described above, and make the quantitative determination of the unknown by applying the reading obtained. For best results the calibration curve and unknown samples should be run on the same day, because the aminophenols tend to darken on standing. Run a suitable blank under the same conditions with unimpregnated cloth. Tests were run using various fixatives, laundering agents, and emulsifiers which might be used in cloth impregnation studies. Of these materials, chlorinated paraffin gave the least interference and polyvinyl alcohol gave the greatest. In most cases, compensation for interferences could be made by use of suitable blanks. Results, corrected hy use of blanks, of the fluorometric determination of b e n d in the presence of various agents are listed in Table 11. Gravimetric Method. Recoveries of 97 to 98yGwere obtained in the estimation of benzil by a method for the determination of water-insoluble carbonyl compounds by means of 2,4-dinitrophenylhydrazine (6). The method used was essentially the same as described by Iddles et al. u ith the addition of a 2-hour estraction of the cloth sample with 95% ethyl alcohol, followed by the precipitation of the benzil compound from an aliquot portion of the extract.
LITERATURE CITED
Cross, H. F., J . Econ. EntOVIOl., 41, 731-4 (1948). Cross, H. F., and S n y d e r , F. XI., Soap Sanit. Chemicals, 25,No. 2, 135-49 (1949).
Farbenfabriken, fornierly E riedlander, Bayer, and Co., German Patent 57,151 (1891). Goldenson, J., and Sass, S., Office of Technical Services, r.S. Dept. Commerce, Rept. PB 78709 (1947). Iddles, H. A., Lon,, A. W., Rosen, B. D., and Hart, R. T., Im. ENG.CHEM.,h ~ aED., ~ . 11, 102 (1939). International Critical Tables, Vol. V , p . 378, New York, McGraxHill Book Co., 1929. King, W.V., Ani. J . T r o p . M c d . , 28, 487-97 (1948). RECEIVED July
1 , 1950.
Colorimetric Method for Determination of Traces of Carbonyl Compounds GERALD R . LAPPIN, University of .Arizona, Tucson, .4riz., AND
LELAND C . CLARK, Fels Research I n s t i t u t e f o r t h e S t u d y of H u m a n Derelopment, A n t i o c h College, Yellow Springs, Ohio H E addition of a solution of sodium or potassium hydroxide Tto an alcoholic solution of a 2,4-dinitrophenylhydrazone produces a very intense wine-red color, presumably due to the formation of the resonating quinoidal ion I. A similar quinoidal ion
NO?
has been suggested for the colored solution formed when base is added t o the phenylhydrazone of a nitroaromatic aldehyde (1). This color reaction has been made the basis of a very sensitive method for the estimation of ketosteroids in biological extracts ( 2 ) . Herein is reported the extension of the method to the quantitative determination of traces of aldehydes or ketones in water, organic solvents, or organic reaction products. The method is to most useful in the range of carbonyl concentration from
10-8 molar, wherein fern if any other methods give reliable results or are of general application. Absorption spectra were run on alkaline alcoholic solutions of a number of 2,4-dinitrophenylhydrazones. It was found that the position of the maximum as well as the value of E,,, was nrarly independent of the structure of the carbonyl compound (with exceptions noted below) and were independent of the concentration of base as long as a sufficient excess was present. The colors formed were relatively stable, although slow fading over a period of several days was noted. Beer’s law was obeyed in the condetermined for a centration range studied. The value of E,,, large number of compounds averaged 2.72 X lo4 a t 480 mp. Table I gives more exact values for a number of compounds. For actual analysis it was found unnecessary to isolate the phenylhydrazone. If it was prepared in solution, using a n excess of 2,4-dinitrophenylhydrazine,the addition of base converted the excess reagent to a very light yellow substance, the absorption of which was corrected for by using a blank determination. PREPARATION OF R E 4 G E N T S
Carbonyl-Free Methanol. To 500 ml. of C.P. methanol were added about 5 grams of 2,4-dinitrophenylhydrazineand a few
ANALYTICAL CHEMISTRY
542 Table 1. Position and Values of Emax.for Various Compounds \laxiimi~n Coinpniind
1,,p
x
Ema,.
Arrtaldehydz .iretone lcetophenone .iniealdehyde .icetylacetonr .icetthienonr Renraldehyde Biityraldehg.de Cinnamaldehydc Pyrlohexanone Cyclopentanonr 8,R-Dirhlorobenznliteli).lil.
480 480 480
2.71 z.70 .a, 42 2.71 2.72 2.73 2.70 2.69 2.68 2.70
E'iirfiiral
Jig
~
!J-liep
