84 Detection of Adulterations. 



united ; which last though partially or wholly decomposed, will 

 act upon vegetable blue colors.* We must not attempt to con- 

 vert this hyposulphite to a sulphate, by chlorate of potash, because 

 more sulphuric acid will be formed than the base of the hyposulphite 

 can saturate : and this excess, acting upon the carbonate, will dimin- 

 ish the apparent saturating power of the specimen. 



Sulphate of Magnesia. — This salt is liable to be mixed with sul- 

 phate of soda, which has even been substituted for it. When the 

 latter is the case, the fact is easily discovered, by adding an alkaline 

 carbonate to a solution of the salt; from which, if it be sulphate of 

 soda, no precipitate will occur. When the two salts are mixed, it 

 becomes necessary to ascertain the quantity of magnesia contained 

 in any given weight. For this purpose dry some of the salt by ex- 

 posure to a heat below redness, and dissolve 120 grains of the dried 

 mass in boiling water. Add to the solution a small excess of car- 

 bonate of soda, and continue boiling for some minutes. The pre- 

 cipitate being washed, dried, strongly calcined, and weighed, gives 

 the quantity of magnesia; which should be 40 grains. The quan- 

 tity actually obtained will, however, be somewhat less ; as the alka- 

 line carbonates do not completely precipitate the magnesia. This 

 slight error may be avoided by employing pure potash as the precipi- 

 tant, instead of carbonate of soda. To obtain a more direct proof 

 of the presence and quantity of the sulphate of soda, dissolve a 

 known weight of the salt in water and add a solution of hydrochlo- 

 rateof barytes, in just sufficient quantity to precipitate the whole of 

 the sulphuric acid ; observing to add no more when it ceases to form 

 a precipitate. Filter, wash the precipitate, add the washings to the 

 filtered liquid, and evaporate to dryness. Pour alcohol upon the dry 

 mass. The hydrochlorate of magnesia will be dissolved, while com- 

 mon salt will remain ; very little being taken up by the alcohol, if 

 the latter be pure. Sixty parts of common salt, when dry, indicate 

 seventy-two of dry or one hundred and sixty two of crystallized sul- 

 phate of soda. 



Sulphate of Quinine. — The high price of this article has led to 

 its adulteration with several substances. It should consist of deli- 

 cate, white, silky crystals, having a very bitter taste, and soluble in 

 thirty parts of boiling water, or seven hundred and forty parts of 

 cold water. With potash, soda, and ammonia, it yields a white, 



Pcobably the effect of sulphurous acid. 



