156 OILY OXIDES NOT SAPONIFIABLE. 



It is composed of very minute white filaments, distinguishable 

 only under the microscope. It melts, when heated, to 97, has no 

 acid reaction, and, like cholesterin, becomes red when placed in 

 contact with concentrated sulphuric acid. It does not form an 

 emulsion with cold water, and when the liquid is heated, the se- 

 rolin floats on the surface under the form of a colourless oil. 

 Sulphuric ether dissolves it readily even without the assistance of 

 heat. Alcohol of 0-842 dissolves only a minute trace of it when 

 boiling-hot, and it is not in the least soluble in cold alcohol. It 

 was digested for six hours in potash ley, without being dissolved. 

 Hence, like cholesterin, it seems incapable of forming soap. 

 Acetic and muriatic acids do not act upon it whether they be 

 cold or hot Though long heated in nitric acid, it is not dis- 

 solved ; but it becomes soluble in potash ley, which it colours 

 brown. 



When distilled, it gives out a very characteristic odour, emits 

 ammoniacal vapour, and is partly volatilized. 



SECTION VIII. OF CANTHARIDIN. 



This name has been given to the substance in cantharides or 

 Spanish flies, (Meloe vesicatorius, Lytta vesicatoria, &c.) which 

 occasions a blister when applied to the skin. Its properties were 

 examined by Robiquet in 1810,* and more lately by L. Gmelin. 

 Robiquet obtained it by the following process : 



Cantharides were boiled in water till every thing soluble in that 

 liquid was taken up. The aqueous solution was concentrated to 

 the consistence of a thick syrup, which was repeatedly boiled in 

 alcohol, till that liquid ceased to act upon it The alcoholic so- 

 lution was evaporated to dryness in a gentle heat. The residue 

 was put into a phial with ether, and agitated for a considerable 

 time. After some hours the ether assumed a yellow colour. It 

 was then decanted off", and left to spontaneous evaporation in an 

 open dish. As the ether evaporated, small crystalline plates 

 were deposited mixed with a yellow matter. Alcohol took up 

 the yellow matter, but left the plates. Being dried between folds 

 of blotting-paper, these plates constituted cantharidin in a state 

 of considerable purity. 



Thus obtained, it is in small crystalline plates, resembling mica, 

 which melt, when heated, into a yellow, oleaginous liquid. On 

 cooling, it concretes into a crystalline solid. When heated more 



* Ann. de Chim. Ixxvi. 302. 



