mo On the Purification 
This first washing is then to be drained off., and fresh 
water, in the proportion of ten parts to a hundred, is to 
foe poured on the saltpetre. 
The mixture is to be stirred, and left to soak for the 
space of an hour : the water is then to be again drained 
off 
Fresh water is to be once more poured on the saltpe- 
tre, in the proportion of five parts to a hundred, which 
water, after stirring, is to be immediately drained off. 
This drained saltpetre is then to be put into a caul- 
dron, containing fifty parts of boiling water to a hundred. 
When the saltpetre is dissolved, the solution ought to 
indicate from sixty-six to sixty-eight degrees, by the 
fese -liqueur. 
The solution is then to be carried to a crystalizing 
vessel, in which, by cooling, about two thirds of the 
saltpetre made use of will be precipitated ; the precipita- 
tion begins in about half an hour, and finishes from four 
to six hours afterwards. But, as it is of importance 
that the saltpetre should be obtained in the form of thin 
needles, because in this form it is more easily dried, it is 
necessary that the liquor in the crystalizing vessel should 
be stirred the whole time the precipitation is forming. 
The stirring is performed by means of a kind of rake, 
which gives a slight motion to the mass of liquor, and 
causes the crystals to be precipitated in the form of thin 
needles. 
As the precipitation takes place, the crystals are to be 
brought to the border of the crystalizing vessel ; to be ta- 
ken up with a skimmer, and put to drain in baskets 
placed, for that purpose, upon frames, in such a manner 
that the water which runs from the crystals, may fall 
again into the crystalizing vessel; or it may be received 
in basons placed under the baskets. 
