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PART VI.-ALCOHOL, SPIRITS, LIQUEURS.

ALCOHOL.

§ 228. The term alcohol, in its strict chemical sense, applies only to the neutral compounds of oxygen, carbon, and hydrogen, which, by the action of acids, form ethers. The principal alcohols are enumerated in the following table :—

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Of these ethylic alcohol, wood spirit, and fousel oil are the three of most importance to the analyst.

Ethylic Alcohol, CHO, specific gravity, 0.815 at 0°, 0·79381 at 15.5°; boiling point, 78°3. Absolute alcohol does not dissolve common salt, nor does it give a blue colour when digested with anhydrous sulphate of copper, if perfectly water-free. Filter paper saturated in the following solution-viz., two parts of

citric and one of molybdic acids heated to incipient fusion, and dissolved in 30 to 40 pints of water and dried at 100°, is not bleached when soaked in absolute alcohol; but should water be present, the blue of the paper is entirely discharged. Pure absolute alcohol burns with a white flame, but if water is present with a blue.

There is no cloudy appearance when mixed with water, showing the absence of oily matters. It should be also perfectly neutral to test paper, and leave no residue on evaporation. It must be remembered that, in a commercial sense, "absolute alcohol" is any stronger spirit than can be obtained by ordinary distillation; and, since this is the case, it would be most unwise for any action to be taken under the "Sale of Food and Drugs Act," unless a distinctly fraudulent statement has been made. "Absolute alcohol," as bought over the counters of the chemist, is seldom above from 93 to 95 per cent.

§ 229. Rectified Spirit, as defined by our own pharmacopoeia, should be of specific gravity 0-838; by that of the Netherlands 0.830 to 0.834; of Germany, Switzerland, and Norway, 0.8336; of Austria, 0.838; of France, 0-835 to 0-841. It should be neutral, colourless, volatilising without residue, and free from other alcohols.

Proof Spirit,-a term in constant use for purposes of excise, is a diluted spirit, which was defined by Act of Parliament (58 George III.) to be "such as shall, at the temperature of 100 [51° Fahr.] weigh exactly twelve-thirteenth parts of an equal measure of distilled water." According to Drinkwater it consists of-

Alcohol by weight,
Water by weight,

and its specific gravity at 15°5 is 0.91984.

49.24

50.76

100.00

In the analysis of all spirits (seeing that the terms "proof" and "under proof" are used and known in the trade), the statements of results should always include the percentage of proof spirit.

Spirits weaker than proof are described as U.P., under proof; stronger than proof as O.P., over proof; thus a spirit of 50 U.P. means 50 water and 50 proof spirit, 60 U.P., 60 water and 40 proof spirit. On the other hand, 50 O.P. means that the alcohol is of such a strength, that, to every 100 of the spirit, 50 of water would have to be added to reduce it to proof strength. In all the above the strengths are only good for the normal temperature of 15°.5.

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§230. Excellent tables for the use of analysts have been published both by Mr. Hehner and by Dr. Stevenson. The table on p. 371 will be found, in the absence of the tables mentioned, sufficient for ordinary use; any specific gravity not given can be intercalated by the ordinary rules of arithmetic.

Another method, sometimes called Gröning's, of arriving at the strength of dilute spirits, is based on the fact that the temperature of the vapour is an exact measure of the strength of the alcohol. The bulb of a thermometer is put (on the small scale) into a flask with a bilateral tube, and the temperature of the vapour carefully noted. The following table (XXXIV.) may be used.

The boiling-point is also a useful guide; for within certain limits the boiling-point of alcoholic liquids is not materially altered by admixture with saline and organic matter. A thermometer with a movable scale is employed. Before using it, the thermometer is immersed in boiling distilled water, and the 100° [212° Fahr.] of the scale accurately adjusted to the level of the mercury; it is then ready for an operation of several hours, or even an entire day, if no considerable variations of atmospheric pressure are experienced.

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