Detection of Adulterations. TSf 



of pure iodide contain 125 grains of iodine. We are now directed 

 to redissolve the solid matter contained in the two retorts, and to 

 test them both with nitrate of silver. The solution derived from the 

 pure iodide will, it is said, give no precipitate ; while that obtained 

 from an iodide containing a chloride, will let fall a copious precipi- 

 tate of chloride of silver. This last does not appear probable to us, 

 because the nitric acid must have previously expelled the chlorine ; 

 and this the more completely in proportion to its excess in quantity.* 



Another process of M. Robiquet consists in dissolving in separate 

 portions of water, equal quantities of pure iodide of potassium, and of 

 the preparation to be examined, and precipitating both by nitrate of 

 silver. The liquid being then decanted, and ammonia added, any 

 chloride of silver present will be dissolved, and the weights of the 

 two precipitates vi^ill differ ; while, if both specimens be pure, the 

 ammonia will dissolve nothing, and the weights of both precipitates 

 will be equal. It is quite unnecessary as Bussy and Boutron-Char- 

 lard have shown, to make two solutions ; as 265 grains of iodide of 

 potassium will give with nitrate of silver, a precipitate insoluble in 

 ammonia, and weighing 235 grains. Any deviation from this weight 

 indicates impurity. 



Lemon Juice. — The mineral acids sometimes added to this sub- 

 stance render it unfit for the preparation of lemonade, by giving 

 it irritating properties very injurious in those inflammations of the 

 digestive organs in which lemonade is so frequently and properly 

 used. The means for detecting these will be stated when we treat 

 of vinegar. A more frequent impurity is verjuice and tartaric acid. 

 To detect these, add to a portion of juice, a tolerably concentrated 

 solution of acetate of potash in moderate quantity. If the suspected 

 impurity exist, small crystals will be formed immediately or gradually 

 which will be found to possess the properties of cream of tartar. If 

 the-juice be pure, no crystals will appear ; as the citrate of potash is 

 very soluble. 



Morphine. — This valuable substance generally contains a portion 

 of narcotine, not intentionally added, but resulting from the processes 



* Thenard says, " Quant a I'acide nitrique, il produit sur tous les hydro-chlorates 

 le meme effet que I'acide hydro-chlorique produit sur les nitrates, c'est-k-dire que, 

 mele en exces avec ces sels, il les decompose ^i I'aide d'une legere chaleur, et qu'il 

 en resulte d'une part un nitrate, et de I'autre de Tacide nitreux et du chlore." 

 Traite de Chimie, Paris, 1S27 ; torn, 3, p. 331. 



