Decompofition of dephlogifiicated and inflammable Air. 221 
too great a proportion of dephlogifticated air ; fo the reafon 
why M. Lavoisier and his friends generally produced but 
little acid, .and at laft not at all, muft have been, that the flolv 
combuftion which they made ufe of gave the principle of acidity 
in the dephlogifticated air, and the phlogifton in the inflamma- 
ble air, a better opportunity of efcaping, and forming the phlo- 
gifticated air in their refiduum, of which they have not pub- 
liftied any fatisfa&ory account * ; and it is probable, that the 
weight of thefe elements compared with that of the water 
which forms the balls of the two kinds of air, may be very 
fmall. That excellent philofopher M. Du Luc fuppofes that 
they have even no weight at all. 
M. Lavoisier himfelf, 1 obferve, lays particular ftrefs, (p. 
262.) on the Jlownefs of the combuftion, as if he fufpe&ed it 
to be neceffary to his refult. This circumftarice may alfo 
account for mv want of fuccefs in the attempts that I made to 
repeat his experiment : for whenever I made a ftream of in- 
flammable air to burn in a veffel of dephlogifticated air (which 
I contrived to do by means of a lefs expenfive, but I own a lefs 
accurate, apparatus than his) I always got fome acid, though 
lefs than in my own procefs; but I made a larger and ftronger 
flame than I imagine M. Lavoisier chofe to produce. 
In the courfe of thefe experiments, I found, that when the in- 
flammable air I made ufe of was from turnings of cafl iron , there 
was always a confiderable quantity of fixed air in the refiduum, 
not lefs than one-tenth of a meafure, after the explofion of two 
* Since this was written, Meff. Fotjrcroy, Vauqdelin, and Seguin, have 
publilhed a very particular account of their experiment ; from which it appears, 
that, after the combuftion of the two kinds of air, there was a pretty large refi- 
duum of phlogifticated air, more than was contained in the airs before combuftion. 
See Aimaks de CbimU, for April 179b P’ 35 ’ 
meafures 
