18 
CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. [bull. 167. 
Here no clear and definite fractionation of the water is recognizable, 
at least of such a character as to suggest any other than the ordinary 
formula for calamine. 
Upon boiling powdered calamine with water practically nothing 
went into solution, but by boiling with the solution of sodium car- 
bonate 0.25 per cent of silica was dissolved. After ignition at a red 
heat, only 0.14 per cent of silica became soluble in sodium carbonate, 
and after blasting, only 0.24. In these experiments a very little zinc 
was dissolved also; but there was no evidence that any breaking 
up of the mineral into distinguishable fractions had occurred. In a 
hot 10 per cent solution of caustic soda both the fresh and the ignited 
calamine dissolve almost completely; but boiling with aqueous 
ammonia seems to leave the mineral practically unattacked. All 
experiments aiming to extract a definite fraction of zinc while leaving 
a similar fraction behind resulted negatively. 
By heating with dry ammonium chloride, calamine is vigorously 
attacked, and gains in weight by absorption of chlorine. In two 
experiments the mineral was intimately mixed with three times its 
weight of powdered salammoniac and heated in an air bath for several 
hours to a temperature somewhat over 400°. A large part of the resi- 
due was soluble in water, and the percentage of this portion, together 
with the percentage increase in weight, is given bejow. 
Gain in weight . . 
Soluble in water 
27.60 
53. 23 
II. 
25.78 
67. 13 
A conversion of calamine into the chlorhydrin, Si0 3 (Zn01)> would 
involve a gain in weight of 15.34 per cent. Complete conversion into- 
2ZnCl 2 + Si0 2 implies an increase of #8.14 per cent. The figures given 
lie between these two; and are indefinite also for the reason that there 
was volatilization of zinc chloride. 
In two more experiments the calamine, mingled with three times and 
four times its weight of ammonium chloride, respectively, was heated 
for an hour and a half to bright redness in a combustion tube. The 
zinc chloride which was formed, volatilized, and was collected by suit 
able means for determination. It corresponded to 59.6 and 59.0 per 
cent of the original mineral, calculated as zinc oxide; which indicates 
a nearly complete decomposition of the calamine into 2ZnCl 2 + SiG 2 . 
The residue was mainly silica, with a small part of the zinc, about half 
of the silica being soluble in sodium carbonate solution. Here again 
no definite fractionation of the mineral could be observed. 
Finally the action of dry hydrogen sulphide upon calamine was 
investigated. The mineral was heated to redness in a current of the 
