Mr. Cavennisy’s Experiments on Air. 147 
This is an inftance, that the fuperabundant vitriolic acid may, 
in fome cafes, be better extracted from the bafe it is united to 
by water than by heat. Vitriolated tartar is another inftance; 
for, if vitriolated tartar be mixed with oil of vitriol and expofed 
even to a pretty ftrong red heat, the mafs will be very acid; 
but, if this mafs is diflolved in water, aud evaporated, the crv 
fials will be not fenfibly fo. 
In all probability, the vitriolic acid a&ts in the fame manner in 
the produGtion of dephlogifticated air from alum, as the nitrous 
does in its produétion from nitre ; that is, the watery part comés 
aver firft in the form of dephlogifticated air, leaving the acid 
charged with its phlogifton. Whether this is alfo the cafe 
with regard to green and blue vitriol, or whether in them the 
acid does not rather act in the fame manner as in turbith mine- 
ral, I cannot pretend to fay, but I think the latter more 
likely. | 
There is another way by which dephlogifticated air has been 
found to be produced in great quantities, namely, the growth 
of vegetables expofed to the fun or day-light; the rationale of 
which, in all probability, is, that plants, when affifted by the 
light, deprive part of the water fucked up by their roots of its 
phlogifton, and turn it into dephlogifticated air, while the 
phlogifton unites to, and forms part of, the fubftance of the 
Pern. it 100 
There are many circumftances which fhew, that light has a 
remarkable power in enabling one body to abforb phlogifton 
from another. Mr. Senezier has obferved, that the green 
tinéture procured from the leaves of vegetables by {pirit of wine, 
quickly lofes its colour when expofed to the fun in a bottle’ not 
more than one third part full, but does not do fo in the dark. 
or if the bottle is quite full of the tin@ture, or if the air in it 
’ U2 1S 
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