new Method of preparing Pot-afh. 351 
It muft, however, be remarked, that in thus freeing the 
pot-afh from phlogiftic matter, another impurity is ge- 
nerated : for both the action of fire, and the folution in 
water, convert into earth a portion of the alkaline fait. 
3. No quick-lime appears to be contained in this pot- 
afh : for a folution of it, poured from its fediment, re- 
mained clear, though long expofed to the air. Nor did 
it acquire any milkinefs by being blown into from the 
lungs ; but perhaps the addition of this cauftic fubftance 
would increafe its activity and value, when employed in 
foap-boiling and other arts : for the Ruffian pot-afh is 
more pungent to the tafte, faturates a larger proportion 
of acid, and diffolves oils more powerfully than the pure 
alkaline falts. And Dr. home has proved fd) , that thefe 
qualities depend on a large admixture of quick-lime. 
4. It would be worthy of trial, to afcertain whether 
the large purple fediment, which fubfides when this pot- 
afh is lixiviated, might not be applied to the manufacture 
of Pruffian blue; or ufed in the manner recommended 
by Mr. macquer for dying wool and filk. See the Me- 
moirs of the French Academy for the year 1749.^. 
5. The farmer, though he live at a diftance from the 
manufactures in which pot-afh is employed, may yet 
(d) Eflay on Bleaching. Neumann's Chemiflry, by lewis. 
(e) See alfo neuman’s Chemiilry, by lewis, p, 73. 
find 
