324 ESSAYS anv OBSERVATIONS 
be a vitriolated tartar, which had appear- 
ed in the form of a powder, becaute there 
was not enough of water im the mixture 
to diffolve it. 
LasTLy, I expofed a few ounces of the 
ley in an open thallow veilel fo long, that 
the alkali loft the whole of its caufticity, 
and feemed entirely reftored to the ftate 
of an ordinary fixed alkali ; but it did not 
however depofite a fingle atom of lime. 
And, to affure myfelf that my cauftic ley 
was not of a fingular kind, I repeated the © 
fame experiments with an ordinary foap- 
ley, and with one made by mixing one 
part of a pure fixed alkaline falt with 
three parts of common ftone-lime frefh 
flaked and fifted; nor could I difcover any 
lime in either. The firft of thefe contain- 
ed a {mall quantity of brimftone, and was 
far from being perfectly cauftic, for it 
made a pretty brifk effervefcence with a- 
cids ; but the laft was fo entirely deprived 
of its air, that it did not diminifh in the 
leaft the tranfparency of lime-water. 
THESE experiments feem therefore to 
fupport the fourth propofition, and to 
fhew 
