92 
ON PRECIPITATED CARBONATE OF ZINC. 
precipitate washed till the washings no longer give a preci- 
pitate with a solution of chloride of barium ; when oper- 
ating on three pounds of sulphate of zinc, this usually 
requires three days. 
To secure an elegant preparation — it is necessary that 
the sulphate of zinc should be free from iron ; if not pure, 
it should be rendered so by boiling with a carbonate as 
recommended in the Amer. Jour, of Pharmacy, for 1846, 
page 242. When dry, it can be very easily reduced to a 
powder, which resembles in appearance calcined magnesia. 
It was reasonable to suppose that a cerate made with a 
precipitated carbonate of zinc would be more efficacious 
than one made from a dense powder, as the minute division 
of the former would favour its activity, if its efficacy de- 
pend, as I suppose none will deny, upon the extent of sur- 
face exposed to the action of the fatty materials. 
The cerate is prepared according to the formula of the 
United States Pharmacopoeia, substituting the precipitated 
carbonate of zinc for the calamine. It has a white colour 
very slightly tinged with blue, and remains the same in 
appearance for several months. 
It has been employed in all cases where the usual cala- 
mine cerate would have been used, and, in the opinion of 
the surgeon of the institution, with fully equal, if not 
greater advantage. 
U. S. Naval Hospital, N. Y. Station, April lZth, 1847. 
