MEANS FOR DETERMINING THE PURITY OF DRUGS, ETC. 
5 
be present. Bromide of potassium produces no precipitate with 
bichloride of mercury which will indicate this salt when sold as 
iodide. 
Bitartrate of Potassa. Cream of Tartar. — Bitartrate of po- 
tassa has been adulterated with chalk, tartrate of lime, quartz 
sand, clay, saltpetre, alum, sulphate of potassa, chloride of potas- 
sium, flour , andperhaps other substances. Commercial cream of 
tartar generally contains a little tartrate of lime not intended as an 
adulteration. When pure, cream of tartar is soluble in 184 parts 
of cold and 18 of boiling water, and is insoluble in alcohol. When, 
therefore, five grains of it is agitated with two fluid ounces of dis- 
tilled water, there will be a slight crystalline residue after time 
enough has elapsed to saturate the water, if the salt is pure. If the 
solution is complete and quickly effected, the presence of a more 
soluble salt may be suspected, if an opaque residue is left, one or 
more of the insoluble adulterations are present. Any sulphate 
present may be detected by adding nitrate of baryta to the aque- 
ous solution of the suspected cream oftartar, and treating theprecipi- 
tate with nitric acid, when an insoluble sulphate of baryta remains. 
Chloride of potassium is detected by nitrate of silver which pro- 
duces a white flocculent precipitate insoluble in nitric acid. Any 
insoluble matter will be left when the salt is heated in 20 parts of 
water to ebullition, and under such circumstances flour, if present, 
will be indicated by iodine which colors the liquid blue. 
Nitrate of Potassa. — Saltpetre has been adulterated with 
sulphate of potassa, chloride of sodium, and nitrate of soda. — 
Sulphates are detected by nitrate of baryta, which precipitates 
sulphate of baryta insoluble in nitric acid. Chloride of sodium and 
potassium are indicated by nitrate of silver, which forms with them 
chloride of silver insoluble in nitric acid and soluble in solution 
of ammonia. To prove the purity of the nitrate from nitrate of 
soda, weigh 100 grains, add to it 60 grains of sulphuric acid in a 
deep platina or porcelain crucible covered to prevent loss during the 
desiccation of the salt, and keep it at a red heat till it ceases to 
lose weight. The residue should weigh S6 grains. If less than 
this, and chlorides and sulphates are absent, the saltpetre probably 
contains nitrate of soda. 
Bicarbonate of Soda. — Bicarbonate of soda is extensively used 
both in medicine and for culinary purposes in connection with tar- 
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