20 Mr. woulfe’s Experiments on 
periments, produced no tartar of vitriol; nor have I been 
able to obtain any from the other clays, which I fubmit- 
ted to the fame trials : fuch were the porcellane clay 
from Cornwall, the porcellane clay from Saxony, Stur- 
bridge clay, fuller’s earth, as alfo the blue argilla from 
Paris, which M. beaume lavs is replete with the acid of 
vitriol (b \ and to that he attributes its property of fetting 
free the acids of fait petre and of lea fait; but of this 
more fully hereafter. 
The tobacco-pipe clay, having been deprived of its 
faline part after the calcination, was as white as chalk, 
and had loft its tenacity^. It increafed in weight gr. 
viii. and the alkaly was not only diminilhed in weight, 
but was alfo combined with a portion of the clay; for, 
on fatur.ating it with diftilled vinegar, a gelatinous fub- 
ftance was feparated. I have often obferved the forma- 
tion of this gelatinous matter on the furface of the Vaux- 
hall ftone bottles, in which I had kept for fome months 
(b) M. beaume, in order to demonflrate the acid of vitriol in the clay, has 
boiled it for a confiderable time with fixed alkaly, and thereby obtained tartar of 
vitriol : had he made ufe of a pure alkaly, I would take upon me to fay, that his 
experiment would have failed. The alkaly he ufed contained already tartar of 
vitriol, which became more manifeh; by long boiling, as a portion of the alkaly 
combines with the clay. 
(c ) Might not this be fubhituted in the room of white lead for painters ufe, 
the white lead having many bad qualities, and being very injurious to fome 
other colours h 
oil 
