Mr Davidson on the Adulteration of Fixed Oils. 251 



however unimportant they may be in establishing precise rules 

 for the detection of the very numerous falsifications, they may 

 in some degree contribute to their ultimate improvement. 

 Before describing the experiments which have been made, I 

 shall take notice of the most important facts that are record- 

 ed upon this subject. 



M. Poutet, in 1819, published a memoir upon the falsifica- 

 tion of the oil of olives.* He states, that " the acid nitrate 

 of mercury perfectly solidifies the oil of olives, and leaves 

 fluid and colours yellow-red those of all the oleaginous grains." 

 He directs the acid nitrate of mercury to be prepared by dis- 

 solving without heat, 6 parts of mercury in Ih of nitric acid, 

 sp. gi\ 1.350, 2 drachms of this solution are to be mixed in a 

 phial with three ounces of olive oil, and the mixture is to be 

 agitated every ten minutes for an hour or two. In several 

 hours, varying with the season, it congeals into a yellowish- 

 white mass, and in twenty-four hours is completely solidified, 

 and is more white. When olive oil is adulterated with the 

 oil of any of the oleaginous grains, it does not take a solid mass, 

 but a portion remains liquid, of a yellowish-red or brownish- 

 red colour; and its quantity indicates the proportion of foreign 

 oil. It has since been shewn by M. Boudet that castor oil, 

 and by M. Lescalier, that oil of almonds, are solidified by the 

 acid nitrate of mercury. The presence of castor oil, how- 

 ever, can be determined by another method, which was dis- 

 covered at the same period by M. Planche and M. Rose, 

 viz. its solubility in all proportions, in alcohol of sp. gi". 0.817. 



Roasseau has also pointed out a method for recognising the 

 purity of oil of olives, which is founded upon the property of 

 oil of olives being a better non-conductor of electricity than 

 other vegetable oils. He has demonstrated that its conduct- 

 ing power is G75 times less than any other vegetable oil ; but 

 it must be recollected that the stearine of animal fat is pos- 

 sessed of the same property. M. Felix Boudet published, in 

 1832, a thesis, sheM'ing that the solidification of oils, by the 

 acid nitrate of mercury, is owing to the hyponitrous acid 



* Aimalcsdu Chiiaic ft do Physique, Tomg xii. et Journal do Pliariuacie, 

 Aout Ittrj. 



