2l8 ^ff'Si of Cold on VolalUc Oils. 



between the fingers, like a refin. When placcJ between two capfules of glafs, and es- 

 pofed to the hot wood-aflies, it melted and fublimed in needles. On fufpending tli« 

 operation there remained in the capfule a brown matter, which by cooling cryftallized in a 

 Ariatcd mafs. The needles obtained by fublimation were white and filky, with the tafte 

 and fmell of fennel. On cxpofure to the flame of a candle they liquefied without taking 

 f:re, and by cooling they alTumed a concrete tranfpaient (late. They were infoluble in 

 the nitric acid ; but their folution in alcohol reddened the tindlure of tournfole ; and when 

 fubmitted to evaporation it left a cryftallized matter in filky needles. 



Volatile oil of wormwood, not rectified, and preferved fcveral years in a bottle with the 

 diftillcd water of the fame plant, had depofited a yellowifli matter ; the oil had little fluidity; 

 its colour was of a deep green, and its fmell confiderably pungent; the depofited matter 

 was yellowifh, and emitted the fmell of wormwood ; when applied to the tongue it com- 

 municated the peculiar tafte of the plant ; it adhered to the fingers, like turpentine ; ex- 

 pofure for fome days to the air did not augment its confidence ; when it was afterwards 

 prefented to the flame of a candle, it took fire, and was covered with fmall needles. This 

 matter cryftallized by cooling, and became dry and brittle, like refin. 



The water on which the oil had been preferved very fpeedily reddened the tinclurc of 

 tournfole. 



The volatile oil of fage, diftilled long before, had depofited a concretion which lined the 

 bottom of the bottle in which it was preferved. This concretion was white, and when 

 examined by the magnifier appeared brilliant, cryftallized, and laminated. Before I pro- 

 ceeded to examination I comprefled it between feveral folds of the paper Jofeph, to de- 

 prive it of the oil which might be interpofed between its parts. This concretion, ex- 

 pofed to the air, became dry and friable ; its folution in alcohol became white by the ad- 

 dition of water. Part of the folution, fubje£led to fpontaneous evaporation, left in the 

 capfule a whitifti covering, and fome fmall needles. Expofed to the flame of a candle i: 

 did not take fire, but liquefied, and became firm by cooling, and of a refinous appearance. 

 When placed between two capfules, and fubjefted to a gentle heat, it melted, but only a 

 few particles fublimed. When it was treated comparatively with the camphor of the (hops 

 by the nitric acid, and with the fame degree of heat, the concretion was liquefied, a(rumed 

 the confiftence of turpentine, aiid became much coloured : the camphor, on the contrary, 

 entirely dilTolved in the nitric acid, and was recovered again with its properties by the ad- 

 dition of water. The nitric acid which I heated with the concretion, did not afford the 

 fame refult when treated with a Uke quantity of water. 



From thefe experiments we may conclude, that the concretions obferved in the fever.-J 

 volatile oils, approach ratlier to the nature of refins with a fuperabundance of acid, which 

 form a kind of fait fimilar to the flowers of benzoin * rather than camphor, to which they 



* In 1791, Citizens Dcyeux and Vauquelin informed u5, that the concretions depofiicd by cinnamon-water 

 tud the properties of the acid of benzoin. M. 



That the concijeiions were not camphor, is no doubt afccrtaincd by the different aflion of nitrous acid ; but ho\¥ 

 iix they may agree with tiic acid of benzoin, feems to require further proof. It is generally agreed, from the 

 operiments of LichtcnIleiD and others, that the acidof benzoin is foluble in the vitriolic and nitrous .-icid, 

 and feparable by tlic addition of water, v.iihoui alteration of its properties, aud that it is not readily altered by 

 JigeilioD or abftraftiooof the latter acid. N. 



have 



