ansmit it to the water. I also suspected that metals were not easily
melted or calcined in inflammable, fixed, or nitrous air, or any kind
of diminished air.[8] None of these kinds of air suffered any change by
this operation; nor was there any precipitation of lime, when charcoal
was heated in any of these kinds of air standing in lime-water. This
furnishes another, and I think a pretty decisive proof, that, in the
precipitation of lime by charcoal, the fixed air does not come from the
charcoal, but from the common air. Otherwise it is hard to assign a
reason, why the same degree of heat (or at least a much greater) should
not expel the fixed air from this substance, though surrounded by these
different kinds of air, and why the fixed air might not be transmitted
through them to the lime-water.

Query. May not water impregnated with phlogiston from calcined metals,
or by any other method, be of some use in medicine? The effect of this
impregnation is exceedingly remarkable; but the principle with which it
is impregnated is volatile, and intirely escapes in a day or two, if the
surface of the water be exposed to the common atmosphere.

It should seem that phlogiston is retained more obstinately by charcoal
than it is by lead or tin; for when any given quantity of air is fully
saturated with phlogiston from charcoal, no heat that I have yet applied
has been able to produce any more effect upon it; whereas, in the same
circumstances, lead and tin may still be calcined, at least be made to
emit a copious fume, in which some part of the phlogiston may be set
loose. The air indeed, can take no more; but the water receives it, and
the sides of the phial also receive an addition of incrustation. This is
a white powdery substance, and well deserves to be examined. I shall
endeavour to do it at my leisure.

Lime-water never became turbid by the calcination of metals over it, the
calx immediately seizing the precipitated fixed air, in preference to
the lime in the water; but the colour, smell, and taste of the water was
always changed and the surface of it became covered with a yellow
pellicle, as before.

When this process was made in quicksilver, the air was diminished only
one fifth; and upon water being admitted to it, no more was absorbed;
which is an effect similar to that of a mixture of nitrous and common
air, which was mentioned before.

The preceding experiments on the calcination of metals suggested to me a
method