6-| Mr. kir wan’s Experiments and Obfervations on 
of mercury : and I am Satisfied, from my own trials, that mem 
than 50 grs. would be found unreduced if dephlogifticated ni- 
trous acid had been uled in difiolving the mercury, and the 
folution. performed with iieat and a id rung acid ; but that which 
*Dr. priesxley ufed, being the red or yellow fort, already 
contained much phlogifton, which contributed to the revivifi- 
cation of a larger quantity of mercury than would otherwife 
be found. It is true, that Dr. priestley afterwards revivified 
a great part of what originally remained unreduced ; but this 
happened after it was for fome time expofed to the free air, 
from which the calces of the perfect metals always attract 
phlogifton, as is evident in luna cornua, which blackens on 
•expofure to the air, and hence alio proceed the reductions 
'Operated by Mr. bayen. 
But Dr. pkiestley, to whole luminous experiments chy- 
miftrv is already fo much indebted, has been fo obliging as to 
furnilh me with fome which tend more di refit Jy to elucidate the 
prelent queftion. 
In one experiment lie found that nearly 5 dwts. of minium, 
from whence all its air was extracted, that is, about 118 grs. 
ablorbed 40 oz. meafures of inflammable, that is, 75,8 cubic 
inches 2,65 grs. of phlogifton, and were then reduced : 
*th en ico grs. of minium Ihould require for their reduction 
nearly 2,25 grs. of phlogifton. In another experiment, made 
with more care, he found, that 480 grs. of minium ablorbed 
joB oz. meafures of inflammable air; according to this then 
300 grs. of minium require for their reduction 1,49 grs. of 
phlogifton ; and in two other experiments he found this quan- 
tity ltill lets. Upon which I remark, firft, that the whole of 
the minium was not dephlogifticated ; for, belides that it is 
•never throughout equally calcined, much of it muft have been 
\ reduced 
