a new Eudiometer, i i 3 
then muft the increafe of weight of the bottle M, on adding 
the common air, be .oS of a meafure. Let us now fuppofe, 
that the quantity of common air ufed is 1.02 of a meafure, 
then will the diminution, on adding the common air, be 
1.0S x —d or 1. 1016 of a meafure, and confequently the in- 
1.00 L 
breafe of weight of the bottle M will be 1.1016-1.02 or 
.0816 of a meafure, which is very nearly the fame as if the 
Common air ufed had been exactly one meafure. 
In the fecond method of proceeding, or that in which the 
nitrous air is added to the refpirable, I ufe always the fame 
bottle, namely, that which holds three meafures, and ufe al- 
ways one meafure of refpirable air; and in trying common 
air ufe the fame veffel A as in the firft method ; but fur de- 
phlogifticated air I ufe one that holds 32- meafures. 
In trying the experiment I firfb weigh the bottle M without 
•any air in it, and then weigh it again with the refpirable air 
in it, which gives the quantity of refpirable air ufed. I next 
put the nitrous air into the veflel A, and weigh that and the- 
bottle M together, and then having mixed the airs, weigh them 
again, which gives the diminution. 
From what has been juft laid, it appears, that in this me- 
thod of proceeding I ufe a lefs quantity of nitrous air in trying 
the fame kind of refpirable air than in the former; the reafon 
of which is, that the lame quantity of nitrous air goes further 
in phlogifticating a given quantity of refpirable air in this than 
in the former method, as will be (hewn further on. 
In both thefe methods I exprefs the teft of the air by the 
diminution which they fuffer in mixing ; for example, if the 
diminution on mixing them is two meafures and vV-A> I call 
its teft 2.353, and f© on. 
Vol. LXXIII. 
Q 
In 
