MEANS FOR DETERMINING THE PURITY OF DRUGS, ETC. 107 
ride of calcium plumbago, coal, charcoal in fine powder, bruised 
slate, black oxide of manganese, sulphuret of antiinony, sulphuret of 
lead (galena), iron scales, iodide of sulphur, sand and clay. 
Water has been detected in proportions varying from 5 to 15 
and even 20 per cent, in the commercial iodine. When the quantity 
is unusually large the presence of some deliquescent salt as chloride 
of calcium or magnesium, may be suspected. To detect its pre- 
sence and proportion, first ascertain the absence of fixed impurities 
in the specimen, by heating a portion of it in a capsule. This being 
known, then weigh 100 grains of the iodine and triturate it intimate- 
ly with 200 grains of fused (anhydrous) chloride of calcium, in a 
dry atmosphere, quickly put the mixture in a tarred capsule, and 
heat it to about the temperature of 250o or 300° until all the volatile 
matter has been driven off. Then weigh the capsule and contents, 
yet warm, deduct the tare, and any increase in the weight of 
the chloride may be attributed to water, which is retained by the 
salt at the temperature above stated. 
The Edinburgh Pharm. considers two per cent, of water admis- 
sible, and states that 39 grs. of iodine mixed with 9 gis. of quick 
lime and 3 ounces of water, when heated short of ebullition, 
slowly form a perfect solution, which, if the iodine dots not con- 
tain more than 2 per cent, of water, is colored yellowish or brown- 
ish yellow from excess of iodine, but if more than 2 per cent., 
the solution is colorless. This test merely proves that water is pre- 
sent beyond 2 per cent., and not the real per centage — and further, 
an impure or silicious lime would indicate the absence of water by 
being insufficient to combine with the intended amount of iodine. 
Chloride of Iodine. — Dr. Herzog " considers it remarkable that 
this adulteration has not hitherto been noticed, since in the prepa- 
ration of iodine on the large scale, metallic chlorides, which might 
give rise to the formation of chloride of iodine, are not always 
excluded." This substance gives to iodine a strong disagreeably 
pungent smell, very similar to that of cyanide of iodine. When 
present, it quickly communicates to water, with which the iodine 
has been mixed, a brownish yellow color, and shows by its re- 
action the presence of hydrochloric acid. The quantity of chlo- 
rine is easily detected by converting 100 grs. into iodide and 
chloride, with water and iron filings, precipitating the iron with 
