"British compounds" are defined in sec. 3 of the Spirits Act, 1880, as "spirits redistilled or which have had any flavour communicated thereto, or ingredient or material mixed therewith."

For certain fiscal purposes in connection with allowances on exported spirits, these are "deemed to be plain spirits or spirits in the nature of spirits of wine, unless they are proved to the satisfaction of the Commissioners [of Customs and Excise] to have been distinctly altered in character by redistillation with or by the addition of flavouring matter." (Sec. 5 (2) of Finance Act, 1902, as amended by Sec. 8 of the Revenue Act, 1906.)

There are a few other terms commonly used in dealing with spirits which it may be convenient to mention here.

"Enumerated spirits." - For the purposes of the Customs tariff, brandy, rum, imitation rum, and Geneva are classified as "enumerated" spirits. All other imported spirits are classified as " unenumerated "; they may be either sweetened or unsweetened.

Sweetened spirits are described in the revenue regulations as "spirits to which any matter has been added after distillation, which imparts to them the quality of sweetness and produces obscuration to the amount of over 0.6 per cent."

Liqueurs are not defined by statute, but official regulations describe them, solely from the revenue point of view, as "compounded spirits, the ingredients in which interfere with the correct action of the hydrometer." British liqueurs are deemed to include all sweetened or otherwise "obscured " British compounds, including essences and perfumed spirits, of which the true strength cannot be ascertained without distillation.

Tinctures, as used in pharmacy, are properly preparations obtained (1) by macerating or percolating crude drugs with alcohol (e.g., Tincture of Myrrh, B.P.; Tincture of Krameria, B.P.); or (2) by dissolving definite chemical substances or proximate

1 Ann. Chim. Anal., 1916, 21, 50.55.

• principles in alcohol (Tincture of Ferric Chloride; Tincture of Cantharidin); or (3) by dissolving extracts, etc., of drugs with alcohol (Tincture of Indian Hemp). There are, however, other preparations to which the name "tinctures " has been applied with some qualification - namely, "ethereal " tinctures, and "aqueous" or "glycerin' tinctures. The ethereal tinctures are prepared from certain drugs by substituting ether for alcohol. The aqueous or glycerin tinctures are made by using, instead of alcohol, a mixture of glycerin, water, and acetic acid to extract or dissolve the drug.

"Tinctures," for the purposes of drawback under the British fiscal regulations, include not only medicinal articles such as those indicated above, but also flavouring essences and perfumed spirits. Moreover, spirituous toilet vinegars and waters, dentrifices, hair washes and brilliantines, are also for these special purposes deemed to be "perfumed spirits" and are therefore included as tinctures.

Essences, in British usage where spirits are concerned, are alcoholic solutions of flavourings or perfumes, and sometimes of medicinal substances. In France and some other parts of the Continent, "essence" denotes a volatile oil; in the United States spirituous flavourings, etc., are known as "extracts." Examples of essences are the essences of almonds, lemon, peppermint, and vanilla amongst the flavourings; of ambergris, bergamot, and civet in the perfumes; and of camphor, pepsin, and senna amongst the medicinal preparations. The proportion of dissolved oil or other active substance in the essences varies considerably; thus essence of lemon may contain anything between 5 and 30 per cent. of the essential oil of lemon. Many of the "essences" are quite similar to "spirits" of the same substance except as regards the proportion of dissolved ingredient; and even in this respect there is no necessary difference, though the "spirit" is generally the richer in the active ingredient. Examples are essence of cinnamon and spirit of cinnamon; essence of peppermint and spirit of peppermint. The two ' spirits ' are official in the Pharmacopoeia, and contain, as do most of the other B.P. medicinal spirits, 10 per cent. (by volume) of the respective essential oils. The two essences may contain as little as 2 or 3 per cent. of the oils.

In the United States the Association of Official Agricultural Chemists have agreed upon certain standard strengths for extracts (essences) used in flavouring foodstuffs, as follows: -

Ginger essence (extract) is to contain in 100 c.c. the alcohol. soluble matter of 20 grams of ginger.

Tonka essence is to contain 01 per cent. by weight of coumarin and a corresponding proportion of the other soluble matters of tonka beans.

Vanilla essence is to contain in 100 c.c. the soluble matter of 10 grams of vanilla beans.

The analysis of these various essences, perfumes, spirits, and tinctures, so far as the alcohol is concerned, presents no special difficulty, as a rule. The oils, etc., are extracted with petroleum ether by Thorpe and Holmes's method as described in Chap. VI, the alcohol distilled off from the saturated salt solution, and determined as usual.

For the estimation of the essential oils where the larger proportions are present, the following method can generally be employed.1

To 10 c.c. of the essence pipetted into an ordinary Babcock milk-testing bottle are added in the order given 25 c.c. of cold water, 1 c.c. of hydrochloric acid (sp. gr. 12), and 05 c.c. of chloroform. The mouth of the bottle is closed with the thumb, and the bottle vigorously shaken for not less than a minute. In this way all the oil is dissolved out by the chloroform. The bottle is now whirled in the centrifuge for one and a half to two minutes, and the resulting clear supernatant liquid is removed to within 3 or 4 c.c. by means of a glass tube of small bore connected with an aspirator. To the residue, 1 c.c. of ether is added, and the contents of the bottle well shaken. The bottle held at a slight angle is then placed up to the neck in a boiling water. or steam-bath, in which it is kept for exactly one minute, a gentle rotatory movement being meanwhile imparted to it. The ether present serves to sweep out all traces of the chloroform, when thus treated. Finally, the bottle is cooled, water added to bring the separated oil into the graduated neck, and the volume of the oil observed after centrifuging for half a minute, the reading being taken at the highest part of the meniscus. With the heavier oils, such as wintergreen, diluted sulphuric acid (1:2) is better than water for separating the oil. In this case shaking should be avoided and the temperature kept below 25°.

1 C. D. Howard, J. Amer. Chem. Soc, 1908, 30, 608.