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MEANS FOR DETERMINING THE PURITY OF DRUGS, ETC. 3 
ON THE MEANS FOR DETERMINING THE PURITY OF CERTAIN 
CHEMICALS AND DRUGS, AND FOR DETECTING ADULTERA- 
TIONS. 
[The importance of a knowledge of certain and decisive means for deter- 
mining the purity of chemicals and drugs, to the druggist, apothecary, and 
physician, need hardly be averred. Impressed with this belief, the Phila- 
delphia College of Pharmacy entertained the idea of, and appointed a com- 
mittee to prepare, a small book or pamphlet of test directions for general 
circulation, but various circumstances have prevented that committee from 
accomplishing the task, which presents some difficulties and requires a con- 
siderable expenditure of time. It occurred to us that the object of the Col- 
lege might be gained in a less formal manner by contributions published 
from time to time in this Journal under the above head, without reference to 
any alphabetical or systematic order; and if at a future time, the College 
should deem it advisable, the several articles which may have been publish- 
ed can be arranged and republished in a more compact and systematic form. 
It is intended, to make the notices as complete as possible, to give the reasons 
for the test directions when not so obvious as to render it unnecessary, and 
to base them on the notes appended to substances in the Pharmacopoeia 
when these are deemed sufficiently full to justify it. As no claims to origi- 
nality are preferred by the writers of these articles, they will avail themselves 
of all sources of information, and in most instances without giving reference 
to authorities, which would swell the bulk of the articles unnecessarily. The 
Editor in commencing this work hopes that all who feel disposed to contri- 
bute essays towards the end in view, will freely do so. — Editor.] 
Iodide of Potassium. — Pure iodide of potassium is in opaque 
white, or occasionally in transparent colorless crystals, is dissolved 
by its weight of cold water, and is soluble in alcohol. If diluted 
sulphuric acid be added to its solution in starch water, but little if 
any change is at first perceptible, but gradually it assumes a pur- 
plish tint, and finally after some hours becomes blue. The sulphu- 
ric acid decomposes the salt, producing sulphate of potassa, and 
hydriodic acid, which last is gradually decomposed into iodine and 
water by exposure to the air, causing the gradual coloration of the 
starch. If, however, any iodate of potassa is present, the hydriodic 
acid immediately decomposes it, liberating iodine, which instantly 
colors the starch deep blue. Bichloride of platinum causes a 
brownish red color when added to its aqueous solution, without any 
precipitation of chloro-platinate of potassium. When an excess of 
a strong solution of tartaric acid is added to a strong solution of the 
