lphur without heat. The air is also brought by
electricity to the same state as it is by iron filings and brimstone,
not diminishing common air. If the electric spark be taken in it when it
is confined by water tinged with archil, it is presently changed from
blue to red, and that to a very great degree.

When the iron nails or wires, which I have used to diminish nitrous air,
had done their office, I laid them aside, not suspecting that they could
be of any other philosophical use; but after having lain exposed to the
open air almost a fortnight; having, for some other purpose, put some of
them into a vessel containing common air, standing inverted, and
immersed in water, I was surprized to observe that the air in which they
were confined was diminished. The diminution proceeded so fast, that
the process was completed in about twenty-four hours; for in that time
the air was diminished about one fifth, so that it made no effervescence
with nitrous air, and was, therefore, no doubt, highly noxious, like air
diminished by any other process.

This experiment I have repeated a great number of times, with the same
phials, filled with nails or wires that have been suffered to rust in
nitrous air, but their power of diminishing common air grows less and
less continually. How long it will be before it is quite exhausted I
cannot tell. This diminution of air I conclude must arise from the
phlogiston, either of the nitrous air or the iron, being some way
entangled in the rust, in which the wires were encrusted, and afterwards
getting loose from it.

To the experiments upon iron filings and brimstone in nitrous air, I
must add, that when a pot full of this mixture had absorbed as much as
it could of a jar of nitrous air (which is about three fourths of the
whole) I put fresh nitrous air to it, and it continued to absorb, till
three or four jars full of it disappeared; but the absorption was
exceedingly slow at the last. Also when I drew this pot through the
water, and admitted fresh nitrous air to it, it absorbed another jar
full, and then ceased. But when I scraped off the outer surface of this
mixture, which had been so long exposed to the nitrous air, the
remainder absorbed more of the air.

When I took the top of the mixture which I had scraped off and threw
upon it the focus of a burning-glass, the air in which it was confined
was diminished, and became quite noxious; yet when I endeavoured to get
air from this matter in