24 Mr. kirwan’s 'Experiments , &c.. on ihefpcclfic Gravities * 
472,5 will require 159,7; therefore, if 10,044 g|> of nitre 
contain 2,629 gr. acid, the quantity of this Spirit of nitre re- 
quifitc to give 1 59,7 will be 613,2 nearly, and 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 
hrfb I (hall mention the caufe of this difference in treating of 
tartar vitriolate, for it cannot be intirely attributed to the dif- 
ference of evaporation. 
3d! y. 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 neglecting 
the quantity of water that certainly enters into the compo.fi tion 
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 difiiiling it in a 
ftrong heat for eighteen hours. After the difHllation there re- 
mained in the retort a fub fiance purely alkaline, amounting to 
10 French dr. and 12 gr. Now 2 French oz, = 944 gr. Troy, 
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 final! a difference may fairly be attributed to the 
lofs in transferring from one veffel to another, weighing, filter- 
ing:, evaporating, &c. 
Mr. lavoisier, in the Paris Memoirs for the year 1776, has 
given us, after Dr. priestley, the analyfis of the nitrous acid. 
In 
