34 P Mr. Chenevix's Observations and 'Experiment's 
unlike nitrous gas ; but is peculiarly fetid, and may be compared' 
to that which is emitted by brick-kilns* mixed with that of 
nitrous gas. It differs much from oxygenized muriatic acid gas ; 
the latter being, pungent and penetrating, the other heavy and 
oppressive ; and it does not produce, at least in so great a degree, 
the catarrhal symptoms caused by the other. At the bottom of 
this vapour is a bright orange-coloured liquor, which has the 
same smell as the vapour. This is the acid contained in the 
salt ; and I have proved it to be hyperoxygenized muriatic 
acid. But, although the salt from which the acid is disen- 
gaged be pure, the acid itself is never so; because the very 
' act of disengaging it effects its decomposition, and some of it 
is converted into oxygenized muriatic acid. The colour of litmus 
paper, on this account, is generally destroyed by the liquor. I 
say on this account, because I have some reason to believe, from 
having observed this not to be uniformly the case, that hyper- 
oxygenized muriatic acid reddens the vegetable blues. However, 
it must be considered, that the sulphuric acid used to disengage 
the hyperoxygenized muriatic acid is still present; and we can 
draw no certain conclusion, until we have obtained this acid 
free from all other substances. If to this mixture of hyperoxy- 
genized muriate of potash and sulphuric acid; heat be applied, 
an exceedingly violent explosion, with a white and vivid flash, 
takes place, before the liquor has attained the temperature of 
125 of Fahrenheit. In order to obtain this acid, I attempted 
to distil 500 grains, in a glass retort, in a water bath, with 
every precaution against such accidents as I could not but 
in some measure expect; when, almost as soon as I had 
kindled the fire, I saw, in the bottom of the retort, an ex- 
tremely white, vivid, and rapid flash, which was immediately- 
followed by a loud report. The retort was reduced almost to 
