ON THE IMPURITY OP SOME DRUGS. 183 
white, the residue consisting of heavy white powder, 
which, on being heated on charcoal before the blow-pipe, 
and then digested in acid, gives out the smell of sulpho- 
hydric acid ; and when fused with carbonate of soda and 
digested with water, sulphate of soda is formed and car- 
bonate of barytes remains unacted on. The main con- 
stituent of the commercial calamine is thus, obviously, sul- 
phate of barytes. To ascertain if any zinc was contained 
in the red powder, the acid solution which was boiled upon 
it was mixed with a quantity of caustic ammonia in excess, 
which precipitated the peroxide of iron and alumina. This 
precipitate was filtered, and the ammoniacal liquid which 
passed through the filter was precipitated by oxalate of 
ammonia. The oxalate of lime was thrown on a filter, 
and the washings evaporated to dryness and heated to low 
redness in a platinum capsule. No residue was left; show- 
ing the absence of zinc and magnesia. 
140.11 grains of calamine gave, in one analysis, sulphate 
of barytes and some silica, 128.05 grains ; peroxide of iron 
and alumina, 11.55 grains; water, 0.51 grains; and the re- 
sults of two analyses were as follow : — 
i. 
n. 
Sulphate of barytes, 
88.74 
89.77 
Peroxide of iron and alumina, 
8.01 
5.74 
Carbonate of lime, 
2.90 
4.40 
Water, 
0.35 
0.35 
100. 
100.26 
Dr. Thomson having suggested that the mode in which 
this adulterated article was manufactured was by mixing 
together a portion of the American bole, chalk, and sul- 
phate of barytes, the next object was to examine American 
bole, for the purpose of comparison. The following are the 
results of several analyses of this substance, which is used 
extensively for coloring tooth-powders, &c, by druggists. 
The fourth analysis was made by my brother, Mr. James 
Murdoch : — 
