C in ] 



To ascertain the primary elements of the dif- 

 ferent vegetable principles, and the proportions in 

 which they are combined, different methods of analy- 

 sis have been adopted. The most simple are their de- 

 composition by heat, or their formation into new pro- 

 ducts by combustion. 



When any vegetable principle is acted on by a 

 strong red heat, its elements become newly arranged. 

 Such of them as are volatile are expelled in the gas- 

 eous form ; and are either condensed as fluids, or re- 

 main permanently elastic. The fixed remainder is 

 either carbonaceous, earthy, saline, alkaline, or metal- 

 lic matter. 



To make correct experiments on the decomposi- 

 tion of vegetable substances by heat, requires a com- 

 plicated apparatus, much time and labour, and all the 

 resources of the philosophical chemist ; but such re- 

 sults as are useful to the agriculturist may be easily 

 obtained. The apparatus necessary, is a green glass 

 retort, attached by cement to a receiver, connected 

 with a tube passing under an inverted jar of known 

 capacity, filled with water.* A given weight of the 

 substance is to be heated to redness in the retort over 

 a charcoal fire ; the receiver is to be kept cool, and 

 the process continued as long as any elastic matter is 

 generated. The condensible fluids will collect in the 

 receiver, and the fixed residuum will be found in the 

 retort. The fluid products of the distillation of vege- 

 table substances are principally water, with some 



* See Fig, 14. 



