112 
ON HYDRASTIS CANADENSIS. 
excess preventing the appearance of the precipitate, or redissolving 
after formation. 
Sulphate of Iron. — Pure sulphate of iron is in the form of trans- 
lucent rhombic crystals of a pale bluish green. In dry air it efflo- 
resces and becomes covered with a white powder, but the air being 
moist the color verges more or less on yellowish-brown. It is 
freely soluble in water, but insoluble in alcohol and strong sul- 
phuric acid. Heated moderately it dissolves in its water of crys- 
tallization, nearly all of which gradually evaporates and leaves a 
white powder. At a higher temperature sulphurous acid is evolved 
and a subsesquisulphate formed, and finally at a red heat it 
loses all its acid, leaving a residue, the sesquioxide. The impuri- 
ties generally found in green vitriol are sesquisulphate of iron, sul- 
phate of copper and sulphate of zinc. Sesquisulphate of iron is 
indicated by the grass green hue of the salt, the depth of color in- 
creasing with amount of sesquioxide. When dissolved in water 
previously boiled to drive off dissolved oxygen, pure sulphate gives 
a white precipitate with ferrocyanuret of potassium, while the pre- 
sence of a sesquisalt causes a greenish hue in proportion to the 
amount present. Sulphate of copper is detected by solution in 
water, adding an excess of solution of ammonia and filtering, when 
if this salt be present the nitrate will possess a smalt blue color, 
Sulphate of zinc is detected by the same means, and driving off the 
excess of ammonia by heat, when, if this salt be present, white 
flocculi of oxide of zinc appear. Sulphate of iron may be readily 
deprived of the first two impurities by agitating its solution with, 
or filtration through iron filings. 
ON HYDRASTIS CANADENSIS. 
By Alfred A. B. Durand. 
(An Inaugural Essay.) 
Hydrastis Canadensis. 
Golden seal. Yellow root. Orange root. Yellow puccoon. 
The Hydrastis Canadensis w r as known to the aborgines of North 
America, both as a medicine and as a dye. It is still used in 
