The methods used fall chiefly into three main classes.

In one class the alcohols are not separated from the spirit, but are estimated by means of the colour produced through the action of strong sulphuric acid upon them (Girard and Cuniasse; Savalle;, Government Laboratory).

1 Compare L. Ronnet, Ann. Falsif., 1910, 3, 205.

In the second class, the higher alcohols are extracted from the spirit by means of solvents (carbon tetrachloride, carbon disulphide). Their amount is then determined by conversion into the corresponding acids (Allen-Marquardt), or into the nitrites (Beckmann), or the acetates (Bardy).

In the third class, the higher alcohols are also extracted, chloroform being the solvent, but the quantity is deduced from the increase in the volume of the solvent. (The Rose process, different modifications of which are used in France and Germany.)

After describing the several methods in detail we will offer a few general remarks upon them, indicating what appear to be their relative merits or disadvantages.