Mr. Majfey on Saltpetre 219 
In the firft place, becaufe the wood-afhes ufed 
by the faltpetre • makers, in large towns, are 
generally the refufe of other trades, and contain 
little or no fixt alkali. Thofe that are ufed by 
the faltpetre makers in Paris are of this fort, and 
often afford, upon elixiviation, only a little 
Glauber’s fait, Tartar of vitriol, and above all, 
large quantities of marine fait, of which the tar¬ 
tar of vitriol alone contains any fixt vegetable 
alkali, that can furnifh. the bafis of faltpetre, 
or be of any ufe in decompofing the nitre with 
an earthy bafis. 
Secondly, wood-afhes taking up one third of 
the room in the veffels, in which the lixivium is 
made, there is, of courfe, lefs room for the earth, 
and the faltpetre mult confequently be lefs in 
proportion. 
Thirdly, wood-afhes, being very porous, ab- 
forb a large quantity of water, which they 
obftinately retain, and this water holds a quan¬ 
tity of faltpetre in folution, which is a clear lofs 
in proportion to the quantity of water they 
contain. 
Fourthly, wood-afhes bear a very confiderable 
price in mod parts of France, and we are certain 
this price is fuperior to that of pot-afh, con- 
Hdering the portion of fixt alkali that they re- 
fpe&ively contain. 
Fifthly, thefe afhes are commonly impregnated 
with many grofs parts, and much dirt and filth, 
that 
