In British Guiana, the wash used for the making of Demerara rum is prepared by diluting molasses with water to a specific gravity of about 1.060. It is rendered slightly acid by the addition of a little sulphuric acid, in quantity sufficient to set free more or less of the combined organic acids, but not enough to leave any free sulphuric acid in the wash. The reason for making the wash acid is to guard against excessive propagation of butyric and lactic acid organisms, and to render it more suitable for active alcoholic fermentation. A little ammonium sulphate is sometimes added to serve as yeast food. Thus in rum of the Demerara type

Fig. 42. - still for direct firing.

With retort, rectifier and condenser. As commonly used in the Colonies for making rum and other strong spirits (Blair, Campbell & McLean, Glasgow).

W. Collingwood Williams1 gives analyses of a number of authentic simples of Jamaica rum, the results being summarised below. The

1er alcohols were determined by the Allen-Marquardt method.

1 J. Soc. Chem. Ind., 1907, 26, 499.

Demerara rum.

W, Collingvvood Williams gives the following analyses of Demerara rum: -

Thus it will be seen that the Demerara type of rum differs notably from the Jamaica variety, and more particularly in its low proportion of esters.

Analyses of Martinique rum are given by Bonis,1 as follows. The first four were considered to be of superior quality, the next two of average grade, and the last three of low quality.

Martinique rum.

The fixed acids ranged from 037 to 0.95 per cent., except in the first sample, which showed 2 2 per cent. It will be noted that in these examples the proportion of higher alcohols is usually greater than that of the esters.

As regards other varieties of rum, J. Sanarens2 gives analyses of a number of authenticated samples, and also the results obtained from six samples of "artificial" rum. The maximum and minimum figures are summarised in the following table: -

1 Ann. Falsif., 1909, 12, 521. 2 Ibid., 1913, 6, 488.

The quality of rum is generally considered to depend largely upon the esters, but the other secondary constituents are also important, especially the acids. According to Williams, the proportion of esters is not an absolute measure of quality; but, generally speaking, the higher-priced rums contain higher proportions of esters. A high proportion of aldehydes is considered by the same writer to have a deleterious effect upon the flavour, nullifying in some degree the influence of the esters.

To detect formic acid in rum, the sample should be made slightly alkaline with sodium hydroxide solution and evaporated to near dryness. The residue is then dissolved in water, transferred to a flask, acidified with phosphoric acid, and distilled. On testing the distillate with ammoniacal solution of silver nitrate, or with mercuric chloride solution, reduction is obtained if formic acid was present in the rum. To distinguish between the free and the combined acid, the sample should be carefully neutralised, the esters distilled off and hydrolysed, and the two portions evaporated and treated as above described.

H. Fincke1 has found that Jamaica rum contains 0 0033 to 0 0050 gram of free formic acid per 100 c.c., and 0 0033 to 0 0044 gram of the acid in the form of esters. That is, there are approximately equal quantities in the two forms. In artificial rums, he found the corresponding quantities to be: - Free, 00027 to 00260; combined, traces to 0 0048. It is suggested that this difference may be an aid in distinguishing between genuine Jamaica rum and artificial rum.

Imitation rum or "Artificial rum" is made on the Continent, chiefly in Germany, and to a small extent in this country for exportation purposes. The Customs authorities distinguish between "rum," "rum from Jamaica," and "imitation rum "; and entries of imported spirits as "rum " are not accepted if the spirit comes from ports in countries where the sugar-cane is not grown, unless satisfactory evidence of its having been manufactured in a cane-growing country is produced.

1 Zeitsch. Nahr. Genussm., 1913, 25, 589.

Imitation rum may not be blended in bond with genuine rum for home consumption, but is allowed to be so mixed for exportation.

The imitation rum is made by flavouring and colouring patent. still neutral spirit, produced from grain, beet, or potatoes, with artificial essences. "Flavoured" Jamaica rum with high ester content is also employed to give some little verisimilitude to the imitation product. An essence much used is prepared by distilling a mixture of starch, alcohol, and crude acetic acid with manganese dioxide and sulphuric acid. The distillate contains formic and acetic esters, with alcohol, free acids, and probably other products of the oxidation; it is coloured with caramel if required, and mixed with silent spirit in the desired proportion.

The following analyses of factitious rum supplied to the West African Colonies were made in the Government Laboratory: -