si& C H E M 1 
pared, expofe the mixture in the phial to a very gentle 
h.eat; and the're will be eftervefcence amVtlifengagement 
of nitrous gas. This^gas is an elaftic fluid, without co¬ 
lour or fmell, and does not redden tincture of turnfol. 
It is hurtful to relpiration, neither will it maintain com- 
buflion nor. forward vegetation ; yet it is fuppofed to pre¬ 
vent putrefaction. It has more affinity with caloric than 
nitric acid; liencethis property is made ufe of to take 
away the nitrous gas which injures nitric acid. Expofed 
to the action of caloric in a red-hot porcelain tube, it 
undergoes no alteration ; for this body is not decompofed 
by a red heat, while nitric acid by the'fame means un- 
dergoes a total decompoiitioh ; it would feem, from this 
experiment, that it could lofe, at the utmofl, only that 
portion of oxygen which was "fuperfluous in the compo- 
fition of nitrous acid ; but this do£s not appear to be the 
cafe. For this experiment the following apparatus is con- 
ft rafted, as (hewn in the preceding plate, fig. 3. where 
BB is a porcelain tube laid through a furnace ; A, a glafs 
tube, bent like a fyphon, and terminating in a funnel; 
this tube is adjuded to the bottle C, in which fome cop¬ 
per-filings are put, and through the tube the nitric acid 
is to be poured upon them. At the lower extremity of 
the porcelain tube, a tube of fafety with a bulb, is adapt¬ 
ed, which goes under the inverted jar D. The nitrous 
gas is difengaged, and paffes through the hot porcelain 
tube without being decompofed. 
Van Marum affects, that nitrous acid, if the eleftric 
fpark be pafl'ed through it, is reduced to one third of its 
volume; no longer becomes red in atmofpherical air, but 
is converted into azotic gas and nitrous acid. 
Put pure nitrous gas into a tube, and invert it in the 
pneumatic cifter'n, and introducing fome pure oxygen 
gas ; the vapour becomes red; it is nitrous acid that is 
forming, and which is foon difl'olved in the water, fo that 
it rifes in the tube. If the oxygenous and nitrous gafes 
are pure, not a bubble will remain under the jar; care 
mult be taken to introduce the oxygen gas gently, that 
too much may not get in. Caloric from 30 to 35 0 , 
of the thermometer is difengaged during the operation. 
If the oxygen be not pure, the bubble remaining at the 
upper part of the jar is the reiidue of the azot, of the 
hydrogen, or of the carbonic acid gas, &c. which the 
oxygen gas might have contained; for the latter is im¬ 
mediately abforbed by the nitrous gas. 
Lavoifier obferved, that 073 of-nitrous gas would ob- 
forb 0-40 of oxygen gas. The acid refulting from this 
combination is not perfectly white ; it throws up red va¬ 
pours when united with alkalis or lime. But this will 
be fet in a clear light by the following experiments of 
Humboldt. 1. If nitrous gas be combined with oxygen 
over mercury, no more nitric acid in a liquid form will 
be produced, than there was, water in the apparatus. 
The abforption feems very fmall, becaufe the acid con¬ 
tinues dilated in a gafeous date, till the ammoniacal gas 
is precipitated. 2. Mixtures of nitrous, gas and oxygen 
prelent different volumes in tubes than in wide veflels; 
becaufe in the fird, the nitric acid, railed from the fur- 
• face of the water, remains in a gafeous date; this di- 
■ minilhds the quantity in appearance from 2-6 to i-S, and 
even lower. 3. Thefe fame mixtures of nitrous gas and 
oxygen, do not exhibit abforptions of an equal volume 
with the experiments made in atmolphericai air; and 
acids more or leis oxygenated appear in this cafe to be 
formed. The difference is from 3*2 to 2-8. 4. A mixture 
of azotic gas and oxygen gas differs from the atmofphe¬ 
rical air; becaufe the oxygen of the fird is more free, 
and more inclined to combine with a large quantity of 
nitrous,gas. 5. By taking the refiduum, after a mixture 
of equal parts of nitrous gas and atmofpherical air, and 
analyfing it by means of fulphat of iron, it may be found 
cxaftiy what quantity of oxygen is contained in atmof¬ 
pherical air. 6. Nitrous gas, which afts mod uniformly, 
and which is obtained by acids diluted with water, from 
S T R Y. 
17 to 21 0 of Baume’s aerometer, contains from 0-12 to 
0-15 of azot. 
Nitrous gas with aUnofpheric.air .—Under a bell-glafs 
filled with water, 'and inverted on the (held of the pneu¬ 
matic mercurial cidern,' pals one mealure of nitrous gas 
and two of atmofpherical air. ’ The two fluids combine 
quickly, and diminffh prodigioufly. A brilk heat is ex¬ 
cised ; the vyatef aicends in the bell-glafs, and affiorbs 
all the red vapours which arife from the combination of 
thefe aeriform fluids. 
The property of very pure nitrous gas, (that is, de¬ 
prived of azotic gas,) of rapidly abforbing'the oxygen 
of htmofphericnl air, gave PrielHey and Fontana the idea 
of their eudiometer, a word which fignifies a meafure for 
air-, and m fact its delfination is to meafure the oxygen, 
contained m atmofpherical air. The proof conlids in 
employing known quantities of thefe two gafes, and to 
ob'ferve how much is rieceflary to their complete and-re- 
ciprocal faturation 5 the lefs of common air is neceflary 
for faturating the nitrous gas, the more pure is that air, 
and ‘vice ‘verfa. Various inflruments have been contriv¬ 
ed ; thofe or Fontana, Landriani, and Magellan, are the 
mod remarkable. They differ in flrape, but their objeft 
is the fame, namely, to determine the falubrity of at¬ 
mospheric air, or any other, in diderent places. Of the 
mod approved of thefe, a plate and delcription will be 
given. 
Nitrous gas fets phofphorus in a flame; it lofes part of 
its volume, and the refult of the combuflion is azotic gas 
and carbonic acid gas, and fulphurous acid. If a lighted 
coal be plunged into nitrous gas, inflammation takes 
place. The fame elfeft takes place with phofphorus : 
fill a bell-glafs with mercury ; introduce the nitrous gas, 
and the inflammation takes place. Mix hydrogen gas 
with nitrous gas, and bring a lighted taper to the orifice 
of the jar; the hydrogen gas will burn, and a green flame 
will be feen. Shake didilled water and nitrous gas toge¬ 
ther, and nitrat of ammoniac will be formed by ade- 
compofition of the water; the effeft of a double affinity. 
The principle ferving to combuflion exids therefore in 
nitrous gas, fince it promotes the inflammation of certain 
combuflible bodies which have a great affinity with oxy¬ 
gen, as fulphure of potaflr, pyrophorus, phofphorated 
hydrogen gas, iron, &c. 
Nitrous g^s combines with fome acids, and particular¬ 
ly with nitrifc acid, on which it beflows new properties. 
By palling nitrous gas into white concentrated nitric acid, 
it is fird produced yellow, then orange-colour, then very 
dark green. If you fake the orange-coloured nitrous 
acid, and mix it with water, nitrous acid of a green- 
emerald colour is produced : take the dark-green nitrous 
acid, mix it with water, and you' have blue nitrous 
tacid. Prieflley found that 100 parts of nitric acid, of 
the weight of fourteen, abforbed in two days 90-29 of 
nitrous gas: he lays, that, when about leven parts were 
abforbed ; the acid affirmed an orange-colour, a green 
when eighteen parts were taken up, and that, when the 
90-29 were combined, it arole in the form of red va¬ 
pours.—This fucceflion of colours is uniform and con- 
flaiit 5 repeated experiments furniffi the fame refults. 
Of NITROUS ACID. 
It will be feen, from the preceding.experiments, that 
nitric acid when yellow, green, &c. contains lefs oxygen 
than when white; for it is evident, that by combining 
nitrous gas, which has itfelf been already 'deprived of a 
part of this principle, the quantity in the nitric acid 
mud be diminifhed. As by this modification the acid 
acquires frelh properties, modern chemids have given it 
the name nitrous acid, to diflinguifh it from that wherein 
the azot is completely faturated with oxygen. 
Nitric acid, loaded with nitrous oxyd, and confequent- 
ly more deconipofable in that part of its compofitlon, 
produces alfo front the fame caufe, much more effeft upon 
x other 
