ESSENTIAL OILS CONTAINING SULPHUR. 901 



water, it is resolved into tribasic camphoric acid, and neutral 

 camphorate of oxide of ethyl, 2EO + C 20 H 14 O 6 . (Malaguti). 



The matter considered as anhydrous camphoric acid, C 10 H 7 O 3 , 

 is obtained pure by crystallizing in alcohol the product of the 

 distillation of camphoric acid. It forms long flat colourless 

 prisms, which are tasteless and insoluble in water. By continued 

 boiling in water this substance is dissolved, and then appears as 

 the hydrated tribasic acid. (Laurent). 



Liquid camphor, C 20 H 16 O ; the elaopten of the oil of cam- 

 phor of commerce. With the same proportions of carbon and 

 hydrogen as solid camphor, it contains only half as much 

 oxygen. The density of the pure oil is 0.9 1 , its boiling point 

 above 212. 



Campholic acid, HO-fC 20 H l7 O 3 . The vapour of camphor 

 is entirely absorbed by a dry mixture of hydrate of potash and 

 lime, between 300 and 400 centig., without the disengagement 

 of any gas, and campholate of potash formed. This acid has 

 the consistence of camphor, is insoluble in water, and easily 

 saturates bases; it is camphor plus 2HO. (Delalande, Ann. 

 de Chim. etc. 3 ser. i. 120.) Campholic acid, distilled with 

 anhydrous phosphoric acid yields a hydrocarbon, C 18 H 16 ,=4 

 volumes of vapour. (Delalande.) 



Camphrone, C 20 H 21 O ; was obtained by M. Fremy, by 

 dropping fragments of camphor into a porcelain tube contain- 

 ing quicklime heated to redness. It is a light oil, boiling at 167, 

 soluble in alcohol and ether but insoluble in water. 



C. ESSENTIAL OILS CONTAINING SULPHUR. 



Volatile oil of mustard, C 8 H 5 NS 2 . Both black and white mus- 

 tard seeds yield a fat oil by expression. The black seed, when 

 distilled with water, gives a remarkable volatile oil, which is not 

 contained in the seed, but is the result of the reciprocal action 

 of water and an albuminous substance in the seed, named 

 myrozine by Bussy, upon another crystallizable principle in it, 

 myronic acid, which is soluble in water, and appears to be an 

 acid, although little is known respecting it. This oil is the 

 cause of the acridity of black mustard. The application of 

 boiling water to the mustard, of alcohol, acids or alkalies, which 

 coagulate the albuminous body, prevent the formation of the 

 volatile oil. 



This volatile oil is colourless, heavier than water, of a pain- 



