t 

 Proceedings of the Polytechnic Association. 903 



coloring matter of wine is of some interest, as affording means for 

 detecting adulterations and artificial substitutes of wine. 



The Cause of Moisture in Silk. 

 M. Suida gives, in the Paris Cosmos, an account of his experiments 

 for the purpose of ascertaining what causes silk to absorb small 

 quantities of moisture, which, although not readily manifest to the 

 senses, is easily detected by the hygroscope. It is a well known fact 

 that crude silk is very hygroscopic, and some doubt has existed as to 

 whether tlie exterior gum-like varnish of raw silk, or the interior 

 tlbroine, was the chief seat of this great avidity for moisture. The 

 author has taken a certain quantity of one, and the same kind of silk 

 (the avidity for moisture is by no means the same for all kinds of 

 silk), a portion of which had been deprived of its natural gum, while 

 another portion was in its native state. The result of a very carefully 

 instituted series of experiments is, that the fibroine, that is to say, the 

 essential silk fiber itself, and not its tegumentary parts, gum chiefly, 

 are the seat of the hygroscopic properties of raw, non-dyed silk; the 

 process of dyeing altering the fiber, also effects its hygroscopic pro- 

 perties. In 100 parts of natui-al yellow colored silk, according to 

 Mulder^s analysis, there are of fibroine, 53. 3T; gelatine, 20.66; albu- 

 men, 2I:.4:3 ; wax, 1.39 ; and coloring matter, 0.05. In 100 parts of 

 white, native silk, fibroine, 51.04; gelatine, 19.08; albumen, 25.47; 

 wax, 1.11; resinous and fatty matter, 0.30. 



Cyanine. 

 According to M. Morat, the coloring matter of flowers consists, 

 first, of cyanine, or a blue pigment ; second, a pink or rose colored 

 matter, in reality identical with the first, and only altered by an 

 acidity of the juice ; third, two yellow colored matters, xanthine 

 insoluble in water, and xanthine soluble in that liquid. Cyanine is 

 best prepared from the petals of violets or iris flowers; by means of 

 boiling alcohol a blue solution is obtained, which soon turns brown, 

 but is restored to its primative color by being shaken up in contact 

 with air. In order to obtain the coloring matter in a pure state, the 

 alcoholic solution is evaporated to dryness in a water bath, and the 

 residue taken up with water, wherein the blue pigment is soluble, 

 while fatty matter and resins are left behind ; the aqueous solution 

 is precipitated by means of acetate of lead; tlie ensuing green col- 

 ored precipitate is decomposed by sulphuretted hydrogen, filtered 



