A Method for the Determination of Ethyl Alcohol. ∗

Abstract

Ethyl alcohol is either present as such or it may be formed under certain conditions by many plant and animal cells. It is the chief product of carbohydrate metabolism of non-pathogenic as well as pathogenic yeast-like organisms. 1 Smaller quantities have been found in bacterial and mold cultures. It is found also in blood (0.001 to 0.004%) and tissues (0.0007 to 0.0026%) of animals. 2

The usual physical methods are not applicable to the small amounts found in biological materials, and for this reason chemical methods have been proposed and used with a fair degree of success. The methods of Nicloux 3 and Widmark 4 depend upon oxidation of the alcohol by K₂Cr₂O₇ in the presence of strong H₂SO₄. Varying degrees of oxidation are obtained, depending upon the condition.

In the method which we propose the oxidation is carried out in 2 steps by KMnO₄. It is first oxidized by hot alkaline permanganate (almost quantitatively) to oxalic acid. The latter is then completely oxidized on acidification with H₂SO₄. The low final acidity permits a more accurate iodometric determination of residual oxidizing agent.

The sample, previously deproteinized, is pipetted into a 300 cc. Kjeldahl flask. Talcum is added, and the volume is made up to about 150 cc. Eighty to 100 cc. are distilled into another 300 cc. Kjeldahl flask containing about 50 cc. of cold water. An apparatus similar to, but somewhat larger than that recently described by Bok, 5 is satisfactory.