82 Detection of Adulterations. 



crystallization, a very white sulphate. By this process M. Tilloy 

 obtained nine grains of sulphate from an ounce of bark ; but the 

 common process, on a large scale, affords a greater proportion. 



Among the frauds committed by the venders of bark, is that of 

 selling the article after having extracted the quinine. The quinine 

 being first removed by sulphuric and hydrochloric acid, and the resi- 

 due washed with very dilute ammonia, the bark is dried, mixed with 

 good specimens, and sold. It is stated by M. Chevallier, that the 

 yellow varieties, after being thus treated with sulphuric acid, assume 

 a brown color approaching that of tobacco ; their taste becomes less 

 bitter* and somewhat saline ; and particles of sulphate of ammonia 

 may be detected by a magnifying glass. The gray varieties also 

 assume a brownish color, and a saline taste. The color of the red 

 bark becomes much more intense, and the saline taste is more devel- 

 oped than in the other varieties. 



Phosphate of Soda. — The mode of preparing this salt as we find 

 it in commerce, renders it extremely difficult to procure it in a state 

 of perfect purity ; and indeed it is not required to be so, when em- 

 ployed as a medicine. It is sometimes, however, largely adulterated 

 with sulphate of soda ; and may contain a portion of free carbonate 

 of soda ; both of which would change its action on the system, and 

 impair its value. The phosphate of soda, when crystallized, should 

 lose by exposure to heat, 61*71 per cent, of water.* Its crystals ef- 

 floresce rather slowly ; while those of the sulphate of soda undergo 

 the same change rapidly. The sulphate is neutral, while the phos- 

 phate gives the syrup of violets a green color.f The phosphate has 

 a faint saline taste, without any bitterness : while the sulphate is very 

 bitter. If we take Thomson's analysis as correct, a solution of 168 

 grains of the crystals will give, when completely precipitated by ni- 

 trate of barytes, 106 grains of phosphate of barytes, which should be 

 entirely soluble in pure nitric acid. Should any portion of the pre- 

 cipitate be insoluble in nitric acid, it may be considered as sulphate 

 of barytes, 118 grains of which indicate 162 grains of crystallized 

 sulphate of soda. Should the precipitate effervesce when dissolving 

 in nitric acid, it may be considered as containing carbonate of soda ; 

 the quantity of which may be determined as follows : Dissolve all 

 the soluble part of the precipitate in nitric acid ; thus obtaining a 



* Thomson says 64.285-f- 



r By care, and on a small ^cale it may be made quite neutral. 



