132 AC1PENSER HUSO. 



flat metal pan, with a very little water, and heated just enough to 

 make the parts cohere, when it is dried ; but this is of little value." 



The manufacture of isinglass is carried on during summer only, 

 as frost is said to impair its qualities. It is principally imported 

 from St. Petersburgh, in bales. Four sorts are known in com- 

 merce, viz. long staple, short staple, hook, and leaf. The finest 

 is that which has the longest staple ; it is the thinest, whitest, and 

 most transparent. In London the staple is generally picked in 

 shreds, in which state it is sold ; but as it is frequently adulterated 

 with pieces of bladder, and the dried skins of soles, it should 

 always be purchased in the staple. The fish-skin and pieces of 

 bladder may easily be detected by^heir insolubility in hot Water. 



Isinglass is of a fibrous texture, semi-transparent, and nearly 

 colourless ; its taste is insipid, and it has no smell. It consists of 

 nearly pure gelatin, and is therefore almost entirely soluble in 

 boiling water, forming a pretty firm gelatinous, somewhat opalescent 

 mass. It is soluble in the acids and pure alkalies, but is precipi- 

 tated from its solutions by infusions and decoctions of astringent 

 vegetables, the tannin of which forms with it an insoluble com- 

 pound. The metals in their pure state have no action upon 

 isinglass, but several of the metalic salts precipitate it from its 

 solutions. Alcohol does not dissolve isinglass, but separates it 

 from water, when added to its solution. 



Medical Properties and Uses. — Isinglass dissolved in water 

 or in milk, is sometimes used in medicine as a demulcent, and 

 when rendered grateful by the addition of a little sugar and lemon 

 juice, as a mild nutritive jelly, well adapted to the sick and con- 

 valescent. A solution of this substance in water, with a very 

 small proportion of tincture of benzoin, or of tolu, spread on 

 black silk, is the court-plaister of the shops. But the greatest 

 quantities of isinglass are consumed by wine-merchants and 

 brewers, for fining beer and vinous liquors. 



