Detection of Adulterations^ 73 



To remove every portion of corrosive sublimate from calomel, the 

 latter must be repeatedly washed with large quantities of water, or 

 with a weak solution of hydrochlorate of ammonia. 



Chromate of Lead. — This salt, although not used in medicine, is 

 so valuable in the arts, and the temptation to adulterate it is so strong, 

 that our authors have very judiciously given it a place in their work. 

 Its fine yellow color is so brilliant, that it admits of considerable ad- 

 ditions of foreign matter, without any very notable depreciation of 

 color. The presence of the carbonates of lime and lead is easily 

 detected by the effervescence excited by the action of acids. To 

 determine which of these carbonates is present, we would recom- 

 mend that the hydrochloric solution should be evaporated to dryness, 

 the dry mass washed with water, the solution saturated with am- 

 monia, filtered and then tested with oxalate of ammonia, which will 

 discover lime by a white precipitate. If the paint be mixed with 

 starch, it will afford the usual appearances of vegetable decomposi- 

 tion, when exposed to a low red heat. The sulphate of lime has 

 been employed for the same fraudulent purposes, and with greater 

 success, than the carbonates already mentioned. We shall sometimes 

 succeed in seeing the white particles of this salt, in the yellow mass. 

 When this cannot be accomplished, mix the chromate with one fourth 

 its weight of charcoal, and expose the mixture to a red heat, in a 

 crucible. This will reduce any existing sulphate to a sulphuret, 

 which being thrown into dilute hydrochloric acid, will give the odor 

 of sulphuretted hydrogen. The solution is now to be filtered, satu- 

 rated with ammonia, filtered again, and tested with oxalate of ammo- 

 nia, which will, if lime be present, give the usual precipitate. We 

 would observe, that if this precipitate be very scanty, it probably 

 proceeds from the paper filters, and not from any intentional fraud. 



Copaiva. — It is very difiicult to obtain this article in a state suffi- 

 ciently pure for medical purposes. The chief adulteration is castor 

 oil ; the presence of which may be detected by several processes. 

 M. Henry advises that a drachm of copaiva be boiled with a pint 

 of water, until almost the whole of the water has evaporated. If the 

 copaiva be pure, this process renders it dry and britde ; while, if 

 adulterated with castor oil, it preserves a degree of softness propor- 

 tionate to the degree of impurity. 



M. Blondeau has ascertained that a mixture of four parts of copai- 

 va with one of carbonate (sous-carbonate) of magnesia possesses after 

 standing some hours, the transparency and consistency of a concen- 



VoL. XIX.~No. 1. 10 



