316 MEANS FOR DETERMINING THE PURITY OF DRUGS, ETC. 
Dissolve the sulphate of iron and carbonate of soda, each in 
two pints of the water, filter, and add to each solution two ounces 
of simple syrup. Mix the solutions, and allow the precipitate to 
subside. Pour off the supernatant liquid, and wash the precipi- 
tated carbonate carefully with sweetened water, until the wash- 
ings have no longer a saline taste. Collect the precipitate upon 
a fine muslin strainer, and with gentle pressure express as much of 
the water as possible. Transfer to a porcelain capsule, and add 
gradually the nitric acid, previously diluted with an equal mea- 
sure of water. Mix the sugar with the solution, and dissolve over 
a water bath, stirring from time to time with a glass rod. When 
done, the syrup should be made to measure thirty fluid ounces, by 
the addition of a sufficient quantity of water. 
It does not always happen that the apothecary has on hand an 
acid of known specific gravity, and when this is the case, it will 
answer to add nitric acid diluted with an equal measure of water 
to the carbonate of iron, until dissolved, and the solution posses- 
ses a slightly acid reaction. 
This syrup contains ten grains of dry nitrate of iron, to each 
fluid drachm, and the dose varies from twenty to forty drops. 
MEANS OF DETERMINING THE PURITY OF CERTAIN CHEMICALS 
AND DRUGS, AND FOR DETECTING ADULTERATIONS. 
(Continued from page 106.) 
Carbonate of Potass a, in its medicinal form, is a white granu- 
lar powder, inodorous, and of an acrid alkaline taste, dry and 
not adhering to the sides of the bottle, and an alkaline reaction ; 
very deliquescent, soluble in its own weight of water, insoluble 
in alcohol. At a red heat it loses sixteen per cent, of water, but 
no carbonic acid, and fuses into a transparent liquid. With acid 
it effervesces rapidly. The impurities generally present are chlo- 
ride of potassium, sulphate and silicate of potassa. 
Chloride of potassium is detected by supersaturating a solution 
of the salt with pure nitric acid, and adding nitrate of silver ; a 
