6 io Mr. woulfe’s Experiments to ascertain 
that lead has a greater affinity with this acid than with 
that of fea-falt; it alfo fhews, that this combination of 
lead with acid of vitriol is infoluble. That moft ex- 
cellent chemift Mr. margraf, in his experiments on the 
Bolognian pbofpborus , has ffiewn how the Bolognian 
ftone and other fuch fpars, as well as the gypfa , are de- 
compofed by fixed alkalies ; but, as it was neceflary to 
employ an excefs of alkaly to decompofe them thoroughly, 
the quantity of neutral fait he thereby obtained could 
not be accurately afcertained, on account of its mixture 
with the alkaly. I fo far availed myfelf of this learned 
che mill’s method; but contrived to remove that incon- 
* „ « 
veniency, in fuch a manner that the excefs of alkaly 
was leparated, and the neutral fait left pure. This con- 
fills in faturating the fait with dillilled vinegar, evapo- 
rating the mixture flowly to drynefs, and diflblving the 
fal diureticus , formed by the combination of the vinegar 
and excefs of alkaly, in rectified fpirit of wine, for this 
lalt is very foluble in it; whereas the combinations of the 
acids of vitriol and of fea-falt, with either vegetable or 
marine alkaly, are no way foluble in this fpirit. 1 mull 
here obferve, that no fixed alkaly is quite free from neu- 
tral fait ; but the pureft is that made with good tartar. 
Two drams of the alkaly, I made ufe of for my experi- 
ments, contained two grains of tartar of vitriol, for which 
I made an allowance in all my experiments. The quan- 
tity of neutral fait in any alkaly may be accurately afcer- 
tained by this method; and I can take upon me to fay, 
that 
