V O L U M E 28, NO. 1, J A N U A R Y 1 9 5 6 were then suspended from a trough in a chromatographic jar, saturated Tvith heptane. The moving phase, heptane saturated with phenoxyethanol, n-as added to the trough and the jar was sealed. Twenty hours of development time were found t o be adequate for most separations (see Table I). However, the time can be extended or shortened if necessary. The size of the separated spots was 2 t o 3 cm. in diameter. Inasmuch as the solvent runs off the end of the paper in the time required for most separations, R, values cannot be used for identification of the spots. It is necessary therefore to use standard substances for comparison. Where substances of widely differing mobilities are present in the
133 same mixture, the eluate from the paper can be collected and rechromatographed. LITERATURE CITED
(1) Kirchner, J. G., and Keller, G. J.. J . Am. Chem. SOC.72, 1867
(1950).
( 2 ) Kostir, J. V., and Slavik, K , Coliecfmn Czechoslob. Chem Conrmuns. 15, 17 (1950). (3) Seher, R., and Wettstein, A., Helo. Chim. Acta 35, 276 (191.2,. (4) Rice, R. G., Keller, G. J., and Kirchner, J. G., ANAL. C H E X23, 194 (1951) RECEIYEDfor review August 18, 1955. Accepted October 24, 1955. Investigation supported b y grants from the U. S. Atomic Energy Commission and the Heart Institute of the National Institutes of Health.
Colorimetric Determination of Decaborane Usi Rg N,N-Diethy Inicotinamide DAVID L. HILL, EDWARD I. GIPSON, and JAMES F. HEACOCK Pharmacology Branch, Chemical Corps M e d i c a l Laboratories, Army Chemical Center,
A method for the direct determination of decaborane is based upon the formation of an orange-red solution (maximum absorption 430 to 500 mp) w-ith decaborane and N,N-diethylnicotinamide. Such solutions follow Beer’s law from 20 to 240 y of decaborane per cc. Boric acid, boron salts, protein solutions, diborane, and pentaborane cause no interference with the procedure. The method is applicable to decaborane in aqueous systems as well as in cyclohexane.
I
S C O S S E C T I O S v i t h some biochemical studies with deca-
borane, a convenient method of determining this compound was desired. Because of the known affinity of the boranes for nitrogen (3,4):the possible use for this purpose of the reaction of decaborane with nitrogen heterocyclic compounds vas investigated. Of a variety of such compounds, many gave evidence for reaction with decaborane and two, S-S-diethylnicotinamide and nicotinamide, formed stable orange-red solutions. The color developed with decaborane and S,S-diethylnicotin-
t
o’6
0.4 m
a
0.3
~
370 390 410 430 450 470 490
WAVE LENGTH IN M U Figure 1. Absorption spectrum of solution of N,N-diethylnicotinamide-decaborane adduct in cyclohexane using 100 y of decaborane per cc. Beckman DU spectrophotometer, I-cm. absorption path length
Md.
amide was found applicable t o a quantitative estimation of decaborane. PROCEDURE
Five cubic centimeters of a 25% aqueous solution of L\’,AYdiethj-lnicotinamide were added t o 0.5 cc. of sample containing decaborane. The color development became stabilized in 90 minutes a t room temperature. Readings were taken a t 435 mp using a Beckman DG spectrophotometer. The color reagent may be obtained in this dilution from a number of supply houses under the name of Sikethamide. RESULTS AND DISCUSSION
Solutions of decaborane in cyclohexane n-ere used to determine the absorption curve of the S,AV-diethylnicotinamide-decaborane adduct. As shorn in Figure 1, a broad region of maximum absorption vias obtained b e h e e n 430 and 500 mp. The decaborane used for the standardization curve v-as purified by vacuum sublimation. From a stock solution containing 50 mg. of decaborane in 100 cc. of cyclohexane, dilutions in this solvent were prepared to provide a range of 5 to 200 y per 0.5 CT. of sample used for analysis. Samples containing 10 and 120 y of decaborane gave absorbance values of 0.05 and 0.585>respectively. Within these limits, using five sample concentrations, the concentration of decaborane and the absorbance were rclated linearly. -diethylnicotinamide-decaboraneadduct is nty. Some information of its structure was obtained by comparing its infrared absorption spectrum as a film n-ith that, of a film of decaborane as recorded x i t h a Perkin-Elmer single-beam infrared spectrometer, Model 12 C. Using the frequency assignments determined by Keller and Johnston ( 2 ) ,it appeared that reaction occurred at the B-H B bridge structure of the decaborane molecule, since the absorption bands due to these structures were no longer found in the adduct. Boron compounds not having the bridge structure, such as boric acid and a variety of boron salts, were found to produce no color with the reagent. Although decaborane is insoluble in water, substances such as 1yogelatin or undiluted blood plasma may form stable dispersions of decaborane in loa- concentrations-e.g., 1 mg. per cc. Such dispersions, immediately after preparation, gave readings with the color reagent, corrected for blank values, essentially the same as with equal concentrations of decaborane in cyclohexane. The presence of the proteins did not interfere with color development in the reaction.
A N A L Y T I C A L CHEMISTRY
134 The color reaction with diborane and pentaborane was examined also. S o color was obtained with diborane in the conditions of analysis, probably because of the known ( 5 )rapid rate of hydrolysis of diborane in contact with water. With pentaborane a transitory red color was obtained which almost immediately changed to yellow. Absorption between 430 and 500 nip was negligible in the concentration range used for decaborane. Of these boranes the method thus seems restricted t o decaborane. The reaction of decaborane Tyith N,N-diethylnicotinamide appears to be fundamentally similar to that reported by Hill and Johnston ( 1 ) using quinoline. It has an additional advantage t o
the biochemist, over the quinoline method, in that it is directly applicable to aqueous solutions. LITERATURE CITED
(1) Hill, W. H., and Johnston, hl. S.,. 4 ~ . 4 CHEM. ~. 28, 1300 (1955). (2) Keller, W. E., and Johnston, H. L., J . Ckcrn. Phys. 20, 1749 (1952). (3) Schlesinger, H. I., and Burg, 8.B., Chern. Reus. 31, 1 (1942). (4) Stock, .4.,“Hydrides of Boron and Silicon,” Cornell University Press, Ithaoa, N. Y . , 1933. ( 5 ) Stock, A., and Kuss, E., Ber. 47, 810 (1914). RECEIVED for review September 9. 1955. Bccepted October 13, 1955.
Quantitative Determination of Ethylene Glycol in Water EILEEN R. HESS, CHARLES
B. JORDAN, and HALKEY K. ROSS
Paint and Chemical Laboratory Division, Aberdeen Proving Ground,
A rapid and accurate procedure suitable for large numbers of determinations of ethylene glycol in water has been developed. It is especially useful where greater accuracy than a hydrometer determination is necessary. This procedure can be applied to the determination of glycerol, any vicinal glycol or ketone, ahydroxyaldehyde, ketone, or acid in water, as long as the reaction rates of each substance are within practical limits.
Md.
time which expires from the moment the first drop of acid mixture reaches the sample until the white precipitate appears. A black background will aid in recognizing the appearance of this precipitate. If the precipitate forms in less than 23.5 seconds, dilute a portion of the sample tenfold by volume and repeat the test on this mixture. If the precipitate still forms in less than 23.5 seconds, dilute another portion of the sample one hundredfold by volume and repeat the test on this mixture. I n order t o obtain maximum accuracy, the mixture tested should contain from 0.10 to l . O O ~ oglycol. One of the above dilution ratios will insure this range. NOMOGRAPH
A
RAPID and accurate procedure which utilizes only standard
laboratory equipment has been developed for quantitatively determining ethylene glycol in water. The procedure is hased on the well-known periodate scission of vicinal glycols originally proposed by Malaprade (b), followed by formation of the insoluble silver iodate. The qualitative procedure for the determination of glycols in alkyd resins ( I ) involves the standard reaction, which may be written as follows:
R CHOH
I
R CHOH
A4nomograph has been constructed to facilitate the calculation of glycol percentages. The data obtained on the mixtures containing 0.10 to 1.00% glycol, as shown in Table I, are plotted a8
Table I. Data Establishing Relationship between Ethylene Glycol Concentration and Reaction Time Ethylene Glycol, Weight % 0.0998 0 1995 0 2993 0 3990 0 4988 0 5986 0 6983 0 7981 0 8978 0 9976
+ HI04-+2RCHO + HI03 + HzO “03
I
The test depends on the fact that silver iodate is nearly insoluble in dilute nitric acid, nThereas silver periodate, if formed as such, is soluble. During the investigation of glycol in alkyd resin, it was noted that the amount of nitric acid added in the final glycol determination in the procedure was critical, and that, if the glycol concentrations Tvere varied and the concentration of the acid was held constant, the length of time it took the precipitate to form varied, and this time could be accurately reproduced for each glycol concentration By making use of this information, it was found possible to determine any percentage of ethylene glycol from 0.10 to 100% by standardizing the nitric acid concentration in the test and recording the exact length of time it took for the silver iodate precipitate t o appear. PROCEDURE
Place 2.00 =k 0.01 ml. of the ethylene glycol sample t o be tested in a test tube (22 X l i 5 mm.). Add 2.0 ml. of 0.1N aqueous silver nitrate. Pipet into the test tube 5,O ml. of an acid solution containing 80 ml. of concentrated nitric acid and 4.56 grams of periodic acid (HI04 2H20) per liter of solution. Shake thoroughly. By means of an accurate timer, record the length of
Reaction Time, Seconds (Average of 5 t o 10 Runs) 135 81
i
34 30 27 25
23.5
;:$ \ ‘a 40 20 0
0
I
I
01
0.2
I
I
I
I
I
I
I
0 3 04 0.5 0.6 0.7 0 8 09 \ V i 9b ETHYLENE G L Y C O L
I
I
I
1.0
1.1
C2
Figure 1. Plot of reaction time us. per cent of ethylene glycol by weight
