136 THE ALUMNI JOURNAL 



selected and elaborated the permanganate method. They oxidise in 

 sulphuric acid solution, in the cold, with the powdered salt, and test 

 with morphine-sulphuric acid. The method did not. give satisfaction 

 with distillates from spirits, tinctures, or other aromatic preparations. 



(c) The oxidation with the bichromate-sulphuric acid mixture 

 originated with J. F. Miller (^^). Depending on the concentration of 

 the reagents, temperature, and the duration of treatment, methyl 

 alcohol will be converted into methylal, formaldehyde, or according 

 to Thorpe and Holmes (^''), completely into carbon dioxide and water. 

 A. Trillat (^') says that 0.5 per cent, of methyl alcohol may be de- 

 tected in absolute alcohol by his rather elaborate method, in which 

 five-hour digestion, two distillations, removal of diphenylamine with 

 steam, and a treatment with suspended lead peroxide in acetic acid 

 solution must be made. He modified his method for the treatment of 

 spirits and the method was further modified by J. Wolff (^*). The 

 time of digestion was then shortened to i. hour in the method of 

 E. Voisenet ("), in which the two final fifths of the slowlv distilled 

 liquid are tested with albumin, hydrochloric acid, and nitrous acid. 

 Other aldehydes react, but their color is readily discharged by traces 

 of hydrogen sulphide or sulphur dioxide. L. E. Hinkel (-°) called 

 attention to a rather peculiar phenomenon, namely, that if the bichro- 

 mate mixture be dilute and heat applied, the amount of formaldehyde 

 formed is exceedingly small. He adds that less than 5 per cent, of 

 methyl alcohol cannot be detected with certainty. In his method the 

 last three-fifths of the distillate are tested with a solution of morphine 

 hydrochloride and strong sulphuric acid. 



It was while trying the three most commonly used oxidising agents 

 that difficulties were encountered. A reaction for formaldehyde was 

 often obtained with ethyl alcohol alone or with distillates containing 

 no methyl alcohol. It was not possible to detect small amounts with 

 certainty. The "bichromate" methods were found to be the most re- 

 liable, under certain conditions, though, at best, they are neither sim- 

 ple nor rapid. 



Since the bichromate-sulphuric acid mixture will not only produce 

 methylal and formaldehyde, but will oxidise methyl alcohol com- 

 pletely (^*') to carbon dioxide and water, the use of a weak solution of 

 chromic acid suggested itself. Trials were made with its solutions of 

 varying concentration and without the customary sulphuric acid. The 

 results were encouraging. Digestion at 60° C. was at first practised, 

 but was later found unnecessary. 



