Detection of Adulterations. 85 



flocculent precipitate, partially soluble in an excess of alkali. Tar- 

 taric, oxalic, and gallic acids, and tincture of galls, give precipitates 

 soluble ill excess of acid. 



The sulphate of lime artificially crystallized, closely resembles 

 that of quinine, and has been frequently mixed with it. The fraud 

 may be detected by burning the salt in a crucible ; when, if any 

 gypsum be present, it will not be consumed. The quantity lost in 

 burning gives the weight of the pure sulphate, provided no vegetable 

 matter has been added to the mixture. 



Stearine has been used as an adulteration ; but it is easily recog- 

 nized by its insolubility in dilute sulphuric acid, on the surface of 

 which it floats. When the fluid is heated, the stearine assumes the 

 form of transparent drops, which again become opake on cooling. 



The presence of sugar may be discovered, by dissolving the sul- 

 phate in water, and precipitating by carbonate of potash, observing 

 to avoid an excess of the carbonate. The filtered solution being 

 now evaporated sufiiciently, the taste will become evident ; or the 

 evaporation may be carried to dryness, and the sugar dissolved by 

 alcohol. This process, though effectual, seems superfluous. Would 

 it not be suflicient to wash the sulphate with twice its weight of cold 

 water, and evaporate the fluid to dryness ? This should dissolve all 

 the sugar, but a mere atom of sulphate ; surely not enough to mask 

 the sweetness of the mass. The above process is applicable also to 

 sugar of manna (mannite). 



The existence of sulphate of cinchonine in that of quinine, is not 

 so apt to be detected, as the preceding adulterations. To ascertain 

 whether or not it be present, dissolve the salt in very dilute sulphuric 

 acid, and evaporate at intervals, as long as the liquid afibrds crystals 

 of sulphate of quinine. Add to the remaining liquid, which does 

 not crystallize, a httle carbonate of potash ; then treat the resulting 

 precipitate with alcohol, and evaporate slowly. If sulphate of cin- 

 chonine has been present, the alcohol will afford cinchonine in crys- 

 tals having a bitter taste, insoluble in cold water, soluble in alcohol, 

 and restoring, when thus dissolved, the blue color of vegetable matter 

 reddened by acids. 



Super-tartrate of Potash; Bi-tariraie of Potash. — This salt, as 

 found in commerce, always contains a portion of tartrate of lime, 

 which sometimes amounts to six per cent. This is an accidental 

 impurity, and not an adulteration. It has sometimes been intention- 

 ally mixed with marble, and even with pulverized silicious stones. 



