OBSERVATIONS UPON BLAUD's PILLS. 
57 
the solution is evaporated to dryness and the carbonate is 
then heated to redness. This salt is appreciably pure, and 
should be employed in all pharmaceutic operations, into 
which the carbonate of potassa enters in fixed and determinate 
quantity. We should state, however, that when this salt 
is kept for a long time, although in close vessels, it absorbs 
water, of which from 13 to 15 centiemes are taken up before 
it appears to be moist. This water produces no change in the 
the pills of Blaud, on account of the excess of alkaline car- 
bonate still remaining, but if the same quantity of carbonate 
be always employed, it is better to take that which has been 
recently calcined. These preliminaries established, let us 
proceed to the preparation of the pills. 
It is useless to reduce the two salts separately to fine 
powder, and to mix them by little and little as directed by Dr. 
Blaud. They can be triturated together in an iron mortar, 
but they rapidly become moist, and even liquefy, in conse- 
quence of the solution of the carbonate of potassa in the water 
of crystallization of the sulphate of iron. It is necessary only 
to triturate them until the white particles are no longer seen 
upon the pestle, after which there are several methods of 
finishing the pills. First, this may be done without any ad- 
dition; the trituration is continued for sometime and the mass 
liquefies; then it thickens, and appears ready to solidify, when 
it should be quickly taken out of the mortar and divided into 
pills, which is easily accomplished if there be no delay in the 
operation; if there be, the mass can neither be divided or 
rolled. To remedy this inconvenience, it is again rubbed in 
the mortar with a few drops of water; it then resumes the 
proper consistence, and retains it a sufficient length of time to 
perform the manipulations. 
The pills thus prepared, often exhibit a peculiar phenome- 
non depending upon the second effect of the carbonate of 
potassa upon the sulphate of iron, (the first is to abstract the 
water of crystallization of the sulphate,) which is due to the for- 
mation of a sulphate of potassa and a carbonate of the protoxide 
VOL. V. — NO. 1. 8 
