Formation of Volatile Alkali. -^8 \ 
this arrangement light inflammable air, which is given out 
from water in contact with iron filings, meeting with phlo- 
gifticated air at the inftant of its extrication, combines with it, 
and forms volatile alkali. In order to detect the minute quan- 
tities of volatde alkali, which were thus generated, I fixed to 
the infide of the glafs tube a fmall piece of paper, flained 
with the rind of the blue raddifh. The vegetable blue was 
in twenty-four hours changed to a green colour. As an addi- 
tional proof of the produflion of volatile alkali, I kept in the 
fame tube fome paper, which had been dipped in a folution of 
cupreous nitre, expeffing to fee its colour converted from 
green to blue, by the alkali which was to be produced. The 
green paper became gradually paler, and in a few days the 
blue colour appeared. This experiment affords a very 
fatisfadlory demonftration of the formation of volatile alkali. 
Water and iron filings mixed together yield inflammable air ; 
but if this be given out in contact with phlogifticated air, vola- 
tile alkali is produced. In thefe circumftances a double attrac- 
tion takes place : one part of the water is attracted by the iron ; 
the other is attracted by the phlogifticated air; and the water 
feems by thefe compound affinities to be much more rapidly 
decompofed, than when iron and water are mixed by themlelves. 
Volatile alkali is formed in a very few hours, if nitrous air 
be ufed in dead of the phlogifticated, all other circumftances re- 
maining as in the former experiment. When 1 have made ufe 
of nitrous air not well freed from its acid, bv which the vege- 
table blue colour has been turned red, a fufficient quantity of 
alkali has been generated in twenty-four hours to change it to 
a green. If iron filings and water be expofed to nitrous air 
for a conliderable time, the nitrous air is fo altered that a can- 
dle burns in it with increaled brightnefs, as was obferved by 
Dr. 
