To 20 or 30cc. of wine is added precipitated and finely powdered bitartrate of potash, the whole well shaken and filtered after standing an hour. To the clear solution is added 2 or 3 drops of a 20 per cent. solution of acetate of potash and the whole allowed to stand twelve hours. The shaking and standing of the solution must take place at as nearly as possible the same temperature. If at the end of this time any considerable precipitate has separated out, the quantitative estimation should be undertaken.

Foreign coloring matters are frequently added to red wines, either to brighten and improve the color obtained from the grapes, or, more frequently, to cover up the effects of previous dilution. These colors may be of vegetable origin, obtained from the various vegetable dyes, or by mixing the juice of other highly colored berries or fruits with the wine; or they may be some of the numerous varieties of aniline dyes obtained from coal-tar. A few examples of the vegetable dyes said to be used may be mentioned as follows: Logwood, cochineal, elderberries, whortleberries, red cabbage, beet-root, mallow, indigo, etc.

4450 - No. 13, pt, 3 ---- 7

Very elaborate and extensive schemes for the detection of these coloring matters have been devised, and chemical literature is full of articles written upon the subject, yet the positive identification of any of the vegetable coloring matters used is only very exceptionally carried out. Most of these schemes are based upon the difference in the color of the precipitates given with various reagents, and the coloring matters of the grape resemble so very closely in their behavior others of vegetable origin, and the variations in the amount of tannin present has so great an influence upon the character of the precipitate, that definite conclusions are well-nigh impossible.

The Berlin commission rejects all methods for the detection of vegetable coloring matters as not being capable of yielding positive proof, and gives only methods for the detection of coal-tar colors. The Paris Laboratory, on the other hand, gives a very elaborate scheme for the de-tection of both vegetable and aniline colors, designed to cover all substances likely to be used for such purposes. This scheme is based chiefly upon Gautier's and the French authorities claim that with it a chemist who is expert by long experience can detect the coloration of a wine by either vegetable or mineral foreign matters, though he may not perhaps be able in all cases to identify the particular coloring matter used. These schemes can only be referred to here, as I consider that their value is not sufficient to justify their reproduction.

The detection of aniline coloring matters can be made with tolerable certainty. The following method is essentially that given by the German commission, and originally devised, I believe, by Konig. Two samples of 100cc. each of wine are taken, and shaken up with about 30cc. of ether, after one has been rendered alkaline by the addition of 5cc. of ammonia. After separation has taken place, about 20cc. of the clear ethereal solution from each test are poured off (not filtered) and evaporated spontaneously in porcelain dishes in which are placed threads of pure white wool, about 5 cm. in length. With wines which are free from aniline colors, the wool, with the residue of the ammoniacal solution, remains of a perfectly white color, and the thread in the solution which was not treated with ammonia will be of a brownish color. The presence of fuchsine is readily detected, however; for out of the perfectly colorless ammoniacal ether solution a bright red color will appear as it evaporates, and becomes fixed upon the woolen thread. Those varieties of aniline dyes, which are more readily taken up by ether from acid solutions than from alkaline will be detected by the red coloring of the wool in the ether from the sample which received no addition of ammonia.

The coloring matter may also be extracted by means of amyl alcohol, which color will be discharged from the solvent by ammonia if the aniline dye used be of an acid nature, in which case the amyl alcohol will dissolve little coloring matter from the wine in presence of ammonia.

The diseases of wine may be considered in the light of an adulteration, as it is a fraud to offer wines for sale as pure wines which have undergone a change which alters their composition and renders them unfit for use. The researches of Pasteur on fermentation have shown that nearly all of the diseases of wine are due to the development in them of microscopical vegetable growths, whose germs are carried in the air. Each disease has its own special organism peculiar to itself, which may be detected by the microscope. These different organisms produce the souring, molding, bittering, cloudiness, blackening, etc, of wine. The best wines are said to be the most subject to these alterations; every year large quantities of the finest wines of Burgundy are spoiled by the disease called bittering (l'amer).

In wines that have become entirely unfit for use through the development of one of these diseases the fact is rendered sufficiently evident by the senses, especially to an expert taster. To detect the first beginning of such alteration, however, is more readily done by means of the microscope in the hands of an expert.