THE TECHNOLOGIST. [Oct. 1, 1864. 



100 ON CHEMISTRY APPLIED TO THE ARTS. 



buried in the snow on the banks of the Volga for a long period, by 

 which the isinglass is whitened. Pipes, purses, and lumps are bags 

 which have been cleared but not opened ; and a quality called ribbon 

 is made by rolling the bag and cutting it into strips before shipping it 

 to this country. 



I shall now endeavour to explain to you how the beautiful prepara- 

 tions before you, for which I am indebted to the kindness of Mr. James 

 Vickers, are obtained. The leaf bladder is first softened in water, and 

 rolled out, under high pressure, into thin leaves, which may extend to 

 several feet long ; these in their turn are drawn under a number of 

 revolving knives, making 1,000 revolutions per minute, by which 6,000 

 of the well-known fine threads are produced in every minute. This 

 quality is chiefly used for culinary purposes. For commercial uses the 

 purses or lumps, above mentioned, are chefly employed. These are 

 soaked in water for two or three days, cut^ open, certain useless parts 

 removed, further softened, rolled, and cut into various dimensions, 

 according to the requirements of trade, their chief use being the clarifi- 

 cation of beer and other alcoholic fluids, for which gelatine cannot be 

 employed, because it dissolves in water, whilst isinglass merely swells. 

 The result is that the highly-swollen and extended mass, when poured 

 into beer, wine, or other alcoholic fluids, is, on the one hand, contracted 

 by their alcohol, and, on the other hand, it combines with their tannin, 

 forming an insoluble precipitate, which, as it falls through the liquor, 

 carries with it the impurities in suspension, and thus clarifies the fluid. 

 As isinglass is very slow in swelling out in the water, brewers employ 

 an acid fluid for the purpose, but, strange to say, instead of using pure 

 acetic acid, many of them take sour beer, and thus run the great risk of 

 spoiling their sound beer. I have known instances of great losses 

 occurring in this way, acetous fermentation having been thus spread 

 through an entire brewery during the summer months. As a large 

 quantity of gelatine, cut into shreds, in imitation of isinglass, is sold 

 at the present day, it may be useful to know that detection is very easy 

 by the following method : — Place a small quantity in hot water, in 

 which gelatine will readily dissolve, whilst isinglass will do so very 

 slowly. I cannot conclude the examination of this interesting class of 

 substances without drawing your attention to the fact that osseine, 

 gelatine, chondrine, and isinglass present marked differences in their 

 textures and general properties, although their chemical compositions 

 may be considered identical, thus : — 



Osseine. Gelatine. Chondrine. Isinglass. 

 Carbon . : 

 Hydrogen 

 Nitrogen . 

 Oxygen 



Esculent Nests. — I must not omit to mention, in connection with this 



50-4 



50-0 



50-61 



50-56 



65 



65 



658 



6-90 



169 



17-5 



15-44 



17-79 



262 



26-0 



27-37 



24-75 



