78 Production of Isinglass on the Coasts of India. 



This is gelatine, which is very abundantly diffused throughout 

 the animal kingdom. 



Gelatine is familiarly known to every one in the form of animal 

 jelly, and is found in considerable quantity in different parts of 

 a great variety of animals. It is distinguished from other animal 

 substances, which it may resemble by being soluble in hot, or rather 

 boiling water, and forming a transparent and colourless solution, 

 which on cooling becomes a solid tremulous jelly. This contains so 

 large a proportion of water that it readily reliquifies on being warm- 

 ed. Albumen, which, when liquid or in solution, may be mistaken 

 for gelatine, is distinguished from it by becoming solid when ex- 

 posed to heat. This may be witnessed in the boiling of an egg, the 

 white of which consists of albumen, and was of a glairy consistence 

 previous to the application of heat. 



Gelatine, when pure, is transparent and nearly colourless, devoid 

 of both taste and smell, easily preserved when in a dry state, but 

 soon putrifying when moist. It is soluble in the different dilute 

 acids as well as in the fixed alkalies, but the compounds formed with 

 the latter, do not form a permanent lather with soap. A charac- 

 teristic of gelatine is the copious precipitate which is formed from 

 any of its solutions on the addition of tannin, as in the form of a 

 decoction of oak bark, of galls, or of catechu. The precipitate forms 

 a grey ductile mass which smells like tanned leather, with which it 

 is indeed identical in nature.* The extent to which pure gelatine 

 can unite with water, and still become a solid tremulous mass, has 

 been ascertained by the experiments of Dr. Bostock. He found that 



when water contained no more than JL of its weight of Isinglass, it 



100 



still stiffened completely on cooling, and even if it contained only 

 i5o t the solution was evidently gelatinous when cold, though it 

 did not become concrete. " One of the most remarkable properties 

 of gelatine is," as Dr. Prout says, "its ready convertibility into 

 a sort of sugar, by a process similar to that by which starch may be 

 so converted." 



It has been stated that gelatine is very abundantly diffused through 



the animal kingdom. Thus, though not contained in any of the 



* Corrosive sublimate does not precipitate gelatine, and therefore serves to 

 distinguish it i'roui albumen, as both are precipitated by galls and oak-bark. 



