SEP 6 I9U 



GIFT 



Issued July 14, 1911. 



United States Department of Agriculture, 



BUREAU OF CHEMISTRY Circular No. 74. 

 H. W. WILEY, Chief of Bureau. 



DETECTION AND DETERMINATION OF SMALL QUANTI- 

 TIES OF ETHYL AND METHYL ALCOHOL AND OF 

 FORMIC ACID. 



By RAYMOND F. BACON, 



Assistant Chemist, Division of Foods, Bureau of Chemistry. 



The detection and determination of small percentages of ethyl and 

 methyl alcohol and of formic acid are often of considerable importance 

 in food chemistry. Certain methods which appear to be of special 

 value for this purpose are presented in this paper. 



ETHYL ALCOHOL. 



Ethyl alcohol, formed as a result of the action of the yeasts on 

 sugars, is commonly found as a product of spontaneous fermentative 

 changes in food products. Its presence in sufficient quantities in a 

 fruit, a vegetable, or other food product, indicates decomposition at 

 some time in the history of that substance. The mere detection of 

 this alcohol, however, does not give much information as to the 

 soundness of a food product, since traces of ethyl alcohol alone might 

 not indicate a sufficient degree of chemical change in the fruit or 

 vegetable to render it decomposed in the ordinary sense of the word. 

 Further, mere traces of alcohol might have their origin in esters 

 which give the aroma and taste to the fruit, and not be the result of a 

 fermentation of the sugars present. It also appears to be a debatable 

 proposition whether alcohol is not formed in saccharine solutions by 

 many types of plants when kept under anaerobic conditions. 1 



It is evident, therefore, that not only the detection, but also the 

 quantitative determination of alcohol is necessary to prove decompo- 

 sition of the type represented by alcoholic fermentation. The 

 amount of alcohol which may be present in such a decomposed food 





i Stoklasa, Ber. d. chem. Ges., 1903, 36: 622- Chem. Centrbl., 1904, 1: 961. Takahashi, Chem. Centrbl., 

 1902.2:1330. Conheim, Zts. physiol. Chem., 1903, 39: 348. Batteli, Compt. rend., 1902, 137: 1029. Margnan, 

 Coinpt. rend., 1905, 140: 1124. 

 98785 Cir. 7411 



