PHYSICAL anno LITERARY, 233 
In order to know whether an alkali 
would lofe a part of its air, and ac lire a 
degree of caufticity, when expofed, with 
this prec aution, to the action of a ftrong 
fire, | mixed an ounce and a half of falt of 
tartar with three ounces of black lead, a 
fubftance of any the moft unchangeable 
by chymical operations. This mixture 
I expofed, for feveral hours, in a covered 
crucible, to a fire fomewhat {ftronger than 
what is neceflary to keep falt of tartar in 
fufion. When allowed to cool, I found 
at ftill in the form of a loofe powder; and 
taking out one half, I diluted it with wa= 
ter, and by filtration: obtained a ley, 
which, when poured into a folution of 
white marble in aqua fortis, precipitated 
the marble under the form of a weak 
quick-lime: for the turbid mixture gave 
a green colour to the juice of violets, and 
threw up a cruft like that of lime-water: : 
and the precipitated powder collected and. 
mixed with fale ammoniac immediately 
_ yielded the {cent of the volatile alkali, 
Lest it fhould here be fufpected, that 
_ the alkaline qualities of this mixture, and 
Won. II, Gg of 
