908 NEUTRAL PRINCIPLES PECULIAR TO CERTAIN PLANTS. 



potash, and dissolved by the addition of water. On saturating 

 the last solution after filtration, with acetic acid, chlorophyl 

 precipitates pure, in the condition of beautiful green flocks.. 



Chlorophyl forms, when dried, a bluish green mass, not 

 fusible, insoluble in water, but dissolving of a fine green colour 

 in alcohol, ether, concentrated sulphuric and hydrochloric acids, 

 and precipitated from these solutions by water. Its solution in 

 alkali is green, precipitated by acids and not by water. Chlo- 

 rine converts it first into a yellow substance, afterwards into a 

 colourless fatty matter. Chlorophyl is intermediate in its pro- 

 perties between a fat and a resin. Exposed to the light of the 

 sun, it becomes yellow, and is probably then identical with 

 ocanthophyl 3 the colouring matter of yellow leaves in autumn. 



CLASS II. 



CONSTITUENTS OF PARTICULAR PLANTS, OR FAMILIES OF PLANTS. 



PIPERIX. 



Formula, C 34 H 19 NO 6 (Regnault). 



This is a crystallizable principle in both white and black pep- 

 per first observed by M. Oersted; but not the cause of the acri- 

 mony of pepper, which is due to a peculiar soft resin Pepper is 

 exhausted by means of hot alcohol, the solution distilled to the 

 condition of an extract, and that mixed with dilute alkali, by which 

 the acrid resin is taken up, and the piperin left undissolved as a 

 greenish powder, to be purified by repeated crystallization from 

 alcohol. 



Piperin forms rhomboidal prisms, of which the angles are 

 85.40 / and 94.20', colourless, tasteless, inodorous, fusible at 

 212, not volatile. It is scarcely soluble in water, and but 

 slightly soluble in alcohol ; in cold sulphuric acid it dissolves 

 of a deep red colour. 



ASPARAGIN. 



Formula, C 8 H 7 N 2 O 5 -f 2HO. 



A crystallizable substance, first obtained by Vauquelin and 

 Robiquet, in the juice of asparagus ; it exists also in potatoes, 

 liquorice root, and particularly in the root of Althea afficinalis, 



