150 Dr. Priestley’s Experiments and Obfervations on 
that an acid had been formed. In all the preceding experi- 
ments the dephlogifticated air had been procured from raan- 
ganefe ; and in all the experiments mentioned in this Paper, 
the inflammable air was from iron by water only. 
A great number of ftrong glafs veflfels having been broken 
in thefe experiments, and fometimes with fome hazard to my- 
felf, and the quantity of air that I was able to decompofe in them 
being frnall, I next procured a copper veffel, which contained 
about thirty-fix ounce meafures of air ; and having now no 
other objecl than difeovering the kind of acid that I had pro- 
cured, 1 made repeated experiments in it ; and after every ten 
or twelve explolions collected all the liquid matter I could 
find ; which, as the air had been previoufly confined by water, 
was pretty confiderable, about equal to the weight of the air. 
The liquor that I procured in this manner was always of a 
deep blue or green, being evidently a folution of copper. But it 
alfo contained a redundant acid, as appeared by its turning the 
juice of litmus red. Befides this blue liquor, there was 
always a quantity of fecmingly abraded copper ; for it was 
perfe&ly and quickly diflolved by volatile alkali, as copper 
very minutely divided would have been. 
* In thefe experiments I ufed, at different times, dephlogifti- 
cated air from manganefe, from red precipitate, and from red 
lead, as the mod unexceptionable of all ; and as it was obli- 
gingly furnifhed me by Mr. Keir, the preparation of it may 
be depended upon. There did not, however, appear to be any 
other difference in the liquors produced by means of thefe kinds 
of dephlogifficated air, except in the fhade of the colour ; that 
from manganefe being of the deepefl blue, and that from red 
lead the lighted: ; and tiiis difference might be accidental. 
By 
