24 Mr. kirwan’s Experiments , &c. on the fpecifc Gravities 
47.2.5 will require 159,7; therefore, if 10,044 gr. of nitre 
contain 2,629 gr. acid, the quantity of this Ipirit of nitre re- 
quifite to give 159,7 be 613,2 near ly> a ^d hence the differ- 
ence betwixt us is only about 8 gr. 
2dly. Mr. homberg fays, he found his fait, when evapo- 
rated to drynefs, to weigh 186 gr. more than before ; whereas, 
by my experiment, it fhould weigh but 92,8 gr. more than at 
firft. I fhall mention the caufe of this difference in treating of 
tartar vitriolate, for it cannot be intirely attributed to the dif- 
ference of evaporation. 
3dly. Mr.' homberg infers, that 1 oz. (that is, 472,5 Troy 
gr.) of this fpirit of nitre contains 141 gr. Troy of real 
acid: by my computation it contains but 123,08 gr. of real 
acid. This difference evidently proceeds from his negledling 
the quantity of water that certainly enters into the composition 
of nitre; for he proceeds on this analogy, 621 . 186,6 :: 
472.5 . 141. 
The proportion of fixed alkali I have afligned to nitre is fully 
confirmed by a very curious experiment of Mr. Fontana’s, 
inferted in rozier’s Journal for November 1778. This inge- 
nious' philofopher decompofed 2 oz. of nitre by diftilling it in a 
irrong heat for eighteen hours. After the diftillation there re- 
mained in the retort a lubftance purely alkaline, amounting to 
10 French dr. and 12 gr. Now 2 French oz. = 944 gr. Trov, 
and the alkaline matter amounts to 607 gr. Troy ; and, accord- 
ing to my computation, 944 gr. of nitre fhould contain 625 
of alkali. So fmall a difference may fairly be attributed to the 
lo'fs in transferring from one veffel to another, weighing, filter- 
ing, evaporating, &c. 
Mr. lavoisier, in the Paris Memoirs for the year 1 776, has 
given us, after Dr. priestley, the analyfis of the nitrous acid. 
In 
