INDUSTRIAL AND ENGINEERING CHEMISTRY
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(loa) Grove, D. C., J . Assoc. Oficial Agr. Chem., 24, 465 (1941). (11) Hall, J. A., Chem. Rev., 13, 479 (1933). (12) Hall, R. T., Holcomb, J. H., and Griffin, D. B., IND.ENG. CKEM.,ANAL.ED.,12, 187 (1940). (13) Kremers, R. C., J. Biol. Chem., 50, 31 (1922). (14) Mendelsohn, S., J. Am. Pharm. Assoc., 16, 726 (1927). (15) Nelson, E. K . , J. Assoc. Oficial Agr. Chem., 19, 529 (1936). (16) Parry, E. J., “Chemistry of Essential Oils and Artificial Perfumes”, 4th ed., Vols. I and 11. London, Scott, Greenwood & Son, 1922. (17) Poucher, W. A., ”Perfumes, Cosmetics, and Soaps”, 4th ed., Vols. I, 11,and 111,London, Chapman and Hall, 1936. (18) Power and Kleber, Pharm. Rundschau, 12, 157 (1894); through (16) p. 219. (19) Purdue Univ. Agr. Expt. Sta., Bull. 461 (1941).
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(20) Redemann, C. E., and Lucas, H. J . , IKD. ENG.CHEM.,ANAL. ED.,9, 521 (1937). (21) Rutovskii, B. N., and Travain, A. I., Riechstof. I d . , 4, 124 (1929). (22) Schimmel & Co., “Annual Reports on Essential Oils, Synthetic Perfumes, etc.”, 601 West 26th St.,New York, N. Y., (23) Strauss, H.. IV. Congr. interna. plantes medicinales plantes essences, Paris, p. 270 (1931); through Schimmel Report, p. 4 5 (1933). (24) U. S.Pharmacopoeia, 11th Decennial Revision. Easton, Penna., Mack Printing Co., 1936. (25) Wilson, C. O., J.Am. Pharm. Assoc., to be published in 1942. THISmanuscript was prepared in connection with peppermint oil investigations conducted by the P u r d u e Lnirersity Agricultural Experiment Station.
The Komarowslry Color Reaction for Aliphatic Alcohols Limitations and Sensitivity HAROLD W. COLES AND WILLIAM E. TOURNAY, M e l l o n I n s t i t u t e , P i t t s b u r g h , P e n n a .
Limitations of the Komarowsky color reaction for fusel oil and certain precautions to be observed in its quantitative application to fusel oil determination, using p-dimethylaminobenzaldehyde, are pointed out. Means of increasing the test’s sensitivity, so that it can be used on ethanol, are described. The colored solutions obtained as a result of the Komarowsky reaction have been studied with the Coleman spectrophotometer, and photographed on Kodachrome.
the unsaturated hydrocarbon then combining with t h e aldehyde. The authors have not found the reaction to be so simple as this assumption, because pentene-2, even in high concentration, does not produce a color with p-dimethylaminobenzaldehyde on prolonged boiling. If concentrated sulfuric acid is added to this mixture, the color develops only when the acid reaches a definite concentration. The acid is necessary for the reaction. Sirupy phosphoric acid may be substituted for sulfuric acid, but the intensity of the developed color is less. The intensity of the color depends not only on the concentration of the higher alcohols but also on that of the reagent
0
F T H E several methods described in the literature for the determination of fusel oil, a colorimetric method
based on the Komarov-sky (5) reaction seemed to have obvious advantages over all other methods (7), the two most outstanding being rapidity and satisfactory sensitivity of the reaction for most purposes. However, constant progress in the design of rectifying columns has produced a n ethanol in which the higher aliphatic alcohol content collectively is of the order of 1 to 5 parts per 100,000. A re-examination of the colorimetric method of analysis was therefore necessary with a view to increasing its sensitivity, the study being based on Penniman’s ( 7 ) adaptation of the reaction.
Komarowsliy Reaction This reaction involves the interaction of the higher alcohol, concentrated sulfuric acid, and a n appropriate cyclic aldehyde. It is stated (3, 6 ) that the color is given by hydrocarbons of the CnHpnseries except ethylene. I n general, the reaction is shown by higher alcohols of the paraffin series (1, 4,esters of these alcohols, hydroaromatic alcohols, phenols, and ethylene compounds when present as a straight chain ( 2 ) . Polyalcohols, ortho- and para-substituted phenols, alcoholic and phenolic acids, and aromatic derivatives having an ethylene group and carboxyl group on the side chain do not give the test. It has been assumed that the color formation is due to a dehydration of the alcohol by the sulfuric acid,
WAVE LENGTH MILLIMICRONS
FIGURE 1.
SPECTRAL TRANSMITTaNCE
A . 5 grams per 100 liters of isopropyl alcohol B . Same as A , b u t 2 hours later C . 5 grams per 100 liters of isoamyl alcohol D. Same a s C , b u t 24 hours later Reagent, p-dimethylaminobenzaldehyde. Standard, sulfuric acid plus reagent (in ethanol)
January 15, 1942
ANALYTICAL EDITION
aldehyde and sulfuric acid. The color is more intense on heating, shiftstoward greater intensity with time, occum with all alcohols, and can he followed with a spectrophotometer (a Coleman double monochromator spectrophotometer with 7.5 mfi slit and square cells, Figure 1). The colored complexes cannot he extracted from the sulfuric acid with solvents, but they can be adsorbed on fuller's earth t o give hlue zones. The colored layer may be removed and washed with water until most of the acid is removed, and the colored compounds eluted with alcohol or acetone. The solvent may then be reduced in volume and the color intensity determined with a colorimeter. This procedure offers a way of concentrating the colored compounds from minute amounts of the alcohols present in ethanol, thus overcoming tbe inability of the colorimeter to give accurate results with weakly colored solutions.
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The flasks are placed simultaneously in a bath of vigorously boiling water and are transferred after 20 minutes to an ice-water bath. When cold, the solutions are ready for comparison in the colorimeter (100-mm. cups) or spectrophotometer. The de-aldehyding refluxing with silver sulfate (the authors do not find any of the methods suggested for removal of aldehydes from alcohol entirely satisfactory) is carried out in the apparatus shown in Figures 2 and 3, which is an adaptation of a suggestion of Stout and Schuette (8).
R I ~ S Stubing C, which 7s s i m b k r t e d into the copper t6bina st-
...~. .-:uhing, F , whicgpasses through thk wallof the flask, and th& is ~~~~~~~
~~
~~~
washed into the flask with sodium hydroxide from a 5-cc. pipet.
&tensivelvas in the Penniman mocedure.
nto the condenser Penniman has fully discussed the variables controlling the
:olor reaction, stressing the necessity of accurate time intervals in all steps and accurate volume measurements. AU stirring or shaking of the flask (because of possible bubble formation) is avoided after the heating stage, which is carried out in a suitable water bath permitting the simultaneous heating of six flasks under exactly the same conditions. After heating, the flasks are immersed simultaneously in an enameled pan for coolinFIGURE 2. FUSEL OIL APPARATUSIN REFLUXING POSITTON The Komarowsky color complexes, after elution from fuller's earth with alcohol, shorn color changes when the reaction is shifted from an acid pH to a basic pH or vice versa.
Apparatus and Technique Penniman's (7) procedure for the preparation of the sample has been changed in a few respects for the determination of aliphatic alcohols i n fermented mashes.
FIGURE3. FUSELOIL Appxnnrns IA DISTILL.
