C 108 ] 



the nature of the acid or alkaline matter may be 

 known by applying the tests described page 97,98,100. 

 If the solid matter be sweet to the taste, it must be 

 supposed to contain sugar ; if bitterish, bitter prin- 

 ciple, or extract ; if astringent, tannin : and if it be 

 nearly insipid, it must be principally gum or mucilage. 

 To separate gum or mucilage from the other princi- 

 ples, alcohol must be boiled upon the solid matter, 

 which will dissolve the sugar and the extract, and 

 leave the mucilage ; the weight of which may be as- 

 certained. . 



To separate sugar and extract, the alcohol must 

 be evaporated till crytals begin to fall down, which are 

 sugar ; but they will generally be coloured by some 

 extract, and can only be purified by repeated solu- 

 tions in alcohol. Extract may be separated from su- 

 gar by dissolving the solid, obtained by evaporation 

 from alcohol, in a small quantity of water, and boiling 

 it for a long while in contact with the air. The ex- 

 tract will gradually fall down in the form of an insolu- 

 ble power, and the sugar will remain in solution. 



If tannin exist in the first solution made by cold 

 water, its separation is easily effected by the* process 

 described page 83. The solution of isinglass must be 

 gradually added, to prevent the existence of an excess 

 of animal jelly in the solution, which might be mista- 

 ken for mucilage. 



When the vegetable substance, the subject of ex- 

 periment, will afford no more principles to cold water ? 

 it must be exposed to boiling water. This will unite 

 to starch if there be any, and may likewise take up 



