30 VIVENOIO DEL ROSARIO. 



The fundamental equation is as follows : 



CH 3 - CHO + KHS0 3 -» CH 3 - CH<g^ K 



Since considerable difficulty has been experienced in this laboratory 

 in obtaining accurate results by the official method, probably due in a 

 large measure to the temperature factor, the method of Eipper has been 

 employed to a considerable extent. The following experimental data 

 show that the method gives accurate results. 



EXPERIMENTAL. 



Preparation of the solutions. — Since practically all the aldehyde deter- 

 minations which the commercial analytical chemist has to deal with are 

 in alcoholic beverages, the experiments have been carried out on solutions 

 of aldehyde in 50 per cent alcohol. 



Pure alcoh ol. — Although Vassey 8 says that the purest commercial 

 cologne-spirits is sufficiently pure for use, it always contains some impu- 

 rities. Of these the high-boiling part, i. e., fusel oil, can be removed 

 with considerable ease. The method of Winkler ° as modified by Dunlap, 

 using silver oxide, failed to give an alcohol free from aldehydes. Each 

 100 cubic centimeters of distillate was tested for aldehydes with rosanil- 

 ine-bisulphite solution and the characteristic reaction for aldehydes ob- 

 tained with each portion tested. 



A second method of Girard and Dupre 10 for the purification of alcohol 

 is that recommended by Tollman in his article on whisky. 11 It failed 

 to give satisfactory results in my hands until W. L. Lewis, of the Gov- 

 ernment Laboratory of Chicago, suggested to me to increase the amount 

 of the reageDts used and the length of the time of contact. 



The original method directs that one-thousandth of its weight of pure caustic 

 potash should be added to the alcohol and the whole then warmed for an hour at 

 a temperature near the boiling point, in a flask under a reflux condenser, and then 

 distilled. The alcohol is thus freed from esters and acid. The aldehydes and 

 bases are removed by the addition of 10 grams of metaphenylenediamine hydro- 

 chloride and 1 gram of phosphoric acid (density 1.4531) to each liter of alcohol. 

 The mixture is then warmed under a reflux condenser for one hour at a temperature 

 close to the boiling point and afterwards distilled, the first and last 100 cubic 

 centimeters being rejected. 



By the use of 10 grams of caustic potash instead of 1 gram, and 

 digestion of the solution for one day on a water bath, I secured a more 

 complete saponification of the esters and neutralization of the acids; 

 and by employing, twice the directed amount of metaphenylenediamine 



s Analysis of Potable Spirits. 



'Journ. Am. Chem. Soc. (1906), 28, 397. 



10 Loc cit. 



11 Loc. cit. 



