C 83 3 



quantities of precipitate afforded by infusions of given 

 weights mixed with solutions of glue or isinglass. 



To make experiments of this kind, an ounce or 

 480 grains of the vegetable substance in coarse pow- 

 der, should be acted upon by half a pint of boiling 

 water. The mixture should be frequently stirred, and 

 suffered to stand 24 hours ; the fluid should then be 

 passed through a fine linen cloth and mixed with an 

 equal quantity of solution of gelatine, made by dissolv- 

 ing glue, jelly, or isinglass in hot water, in the pro- 

 portion of a drachm of glue or isinglass, or six table 

 spoonfuls of jelly, to a pint of water. The precipitate 

 should be collected by passing the mixture of the solu- 

 tion and infusion through folds of blotting paper ; and 

 the paper exposed to the air till its contents are quite 

 dry. If pieces of paper of equal weights are used, in 

 cases in which different vegetable substances are em- 

 ployed, the difference of the weights of the papers 

 when dried, will indicate with tolerable accuracy, the 

 quantities of tannin contained by the substances, and 

 their relative value, for the purposes of manufacture. 

 Four tenths of the increase of weight, in grains, must 

 be taken, which will be in relation to the weights in 

 the table. 



Besides the barks already mentioned, there are a 

 number of others which contain the tanning principle. 

 Few barks indeed are entire free from it. It is like- 

 wise found in the wood and leaves of a number of 

 trees and shrubs, and is one of the most generally dif- 

 fused of the vegetable principles. 



A substance very similar to tannin has been 



