Rkilly & HiCKiNBOiTOM — Concentration of Alcoholic Liquors. 239 



•repeated distillation. Boiling point, 99'4-99'5°/755 mm. and density 

 0-8114 at 15-5/15°. 



iso-Butyl and iso-Amyl Alcohols were purified by repeated fractionation of 

 the purest commercial alcohols obtainable. The tso-butyl alcohol had a 

 boiling point of 107-8°/758 mm., and density 0-8063 at 15-5/15-5", -while the 

 z'so-amyl alcohol boiled at 130-5°-131'5°/757 mm., and had a density of 

 0-8158 at 15-5/15-5°. 



Estimation of the Alcohols in the clistillcde. 



The alcohol in the distillate was estimated by two methods — {a) by 

 density, using Perkin's modified arrangement of the pyknometer suggested 

 by Sprengel, and calculation from density tables of alcohol and water 

 mixtures ; (b) by oxidation, the method of Benedict being employed. In the 

 oxidation method the analysis was carried out as follows. To a known 

 volume (2 c.c.) of the alcoholic distillate, which had been suitably diluted: 

 20 c.c. of a standard solution of potassium dichromate in sulphuric acid 

 solution was added cautiously. It was found advisable to cool the alcoholic 

 solution duiing the addition of the chromic acid solution. The oxidation was 

 completed by heating the mixture on a vigorously boiling water bath for five 

 minutes. After diluting the acid- oxidation mixture, ferrous ammonium 

 sulphate was added, and the excess of the latter determined by titration with 

 standard dichromate. The difference in the volume of the dichromate used 

 for the blank experiment and the actual determination is a measure of 

 the alcoholic content of the solution. A factor for converting c.c. of 

 dichromate into weight of alcohol had to be determined for each alcohol by 

 preparing solutions of known concentration. It was found that the con- 

 stants for the primary alcohols, excluding methyl alcohol, were proportioned 

 to the molecular weights. This indicates that the oxidation of these alcohols 

 probably proceeds with the formation of the corresponding acid. 



In the treatment of the ?!.-butyl alcohol with the dichromate reagent, an 

 odour resembling that of an ester was observed. By using an insufficiency 

 of the oxidising agent, the odour became more pronounced, due evidently to 

 greater formation of the ester. This reaction between n-butyl alcohol and 

 potassium dichromate and sulphuric acid was studied in some detail (see 

 later). When the alcohols were only partially soluble in water, a determina= 

 tion of the volumes of each layer was used as an alternative method in 

 determining the alcoholic content of the distillate. In the case of 7i-butyl 

 alcohol, by the use of the w-butyl alcohol-water density curve already prepared 



