358 FOOD AND FOOD ADULTERANTS. 



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, whortle- 

 berries, red cabbage, beet-root, mallow, indigo, &c. 



Very elaborate and extensive schemes for the detection of these col- 

 oring matters have been devised, and chemical literature is full of arti- 

 cles 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 vege- 

 table 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 veg- 

 etable 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 sub- 

 stances 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 lie may 

 not perhaps be able in all cases to identify the particular coloring mat- 

 ter 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 Ger. 

 man commission, and originally devised, I believe, by Konig. Two 

 samples of lOOcc. 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 ammouiacal 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 pres- 

 ence of fuchsine is readily detected, however; for out of the perfectly 

 colorless amraoniacal 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* 



