C H E M I 
other combuftible bodies. Hence it is that nitrous acid 
•flames with phofphorus, the volatile oils, lome metals, 
&c. upon which nitric acid has comparatively but very 
weak effefts. When nitric acid, more or lefs charged 
with nitrous gas, is put in contail with gold, there are 
two attractions which aft fuddenly and together, that of 
the oxygen of the oxyd of azot for the gold, and that 
of the nitric acid for the oxyd of the gold. And thus, 
by charging nitric acid with nitrous gas, Deyeux contriv¬ 
ed to dilfolve gold therein. 
TJie nitrous vapour is a faturated combination of ni¬ 
tric acid and nitrous gas. Thus, if nitric acid and cop¬ 
per be put together into a bottle, nitrous gas is the pro- 
duft. Pal's this nitrous gas into a fecond bottle contain¬ 
ing concentrated nitric acid, nitrous acid is obtained, 
and a nitrous vapour is difengaged. Draw this nitrous 
vapour through potafh, and colleft the gas difengaged 
thereby, nitrous gas and nitrat of potalh will be produc¬ 
ed in the bottle. Hence alkalis have more attraction for 
the nitric acid than this has for the nitrous oxyd; and 
this is the reafon why nitrits are not formed, but nitrats 
only, with fixed alkalis and the nitrous vapour, any more 
than with the fame bales and with liquid nitrous acid. 
If this nitrous vapour be palfed through concentrated 
fulphuric acid, it is obtained in a cryftallifed form. Work 
as follows :—Put filings of copper into a two-necked bot¬ 
tle ; one opening ferves to pour the nitric acid in order 
to difengage the nitrous gas. From one of the apertures 
goes a tube which is lent into another bottle containing 
concentrated nitric acid; this lait bottle is furnilhed with 
another bent tube which goes under a jar two-thirds filled 
with concentrated fulphuric acid. Then difengage the 
nitrous acid, and it runs into the concentrated nitric 
acid: the nitrous vapour rifes, and, as the fulphuric acid 
feizes upon it, it appears in the form of fmall needled 
cryftals. 
If nitrous vapodrbe mixed with oxygen gas, there will 
be no abforption ; but, if this vapour be put into nitric 
acid, an abforption takes place. Fill a bottle with nitrous 
vapour, and add water boiled, or deprived of air by any 
other means; the nitrous vapour will not mix with the 
water; but with water containing air it will mix. 
_ With refpeft to the four metallic acids, there are many 
circumftances in which metals may be united with oxy¬ 
gen ; yet in general they feem reducible to three. The 
firlt is the contaft of air affifted by caloric ; the fecond is 
by the decompofition of water; the third, by that of acids. 
There are four metallic fubftances capable of being com¬ 
pletely acidified: arl'enic, tungften, molybdena, and 
chrome, lately difeovered by Vauquelin. As we can only 
fpeak of them here as having a name among acids in ge¬ 
neral, we (hall hereafter relate the manner of preparing 
them, and their properties, under the reipeftive heads of 
the/'e metallic fubftances. 
Of MURIATIC ACID. 
This acid exifts abundantly in nature, and is united 
with different bales, principally foda, lime, and magnefia. 
Its conftituent parts are unknown. It is not found alone; 
to obtain it therefore, it will be neceffary to difengage it 
from its combinations. It was formerly called marine 
acid, fpirit of fait, acid of fait, See. The manner of ex- 
trafting it will be {hewn when we treat of muriat of foda. 
Muriatic acid, free from every other fubftance, is al¬ 
ways in the form of a permanent gas, which nothing hi¬ 
therto has been able to render liquid. Muriatic acid 
gas may be obtained, r. By diftillation. 2. By feparating 
the muriat of foda by means of fulphuric acid. 3. If it 
be diffolved and concentrated in cold water, it is difen- 
,gaged by heat, and the gas is collefted under jars with 
mercury. Put fuming muriatic acid into a phial or re¬ 
tort ; to the orifice adapt a bent tube, which is to be 
plunged into the ciftern of the mercmial pneumatic ap¬ 
paratus, under a veffel filled with this metallic fluid. Heat 
the liquid gently, and an aeriform fluid is difengaged, 
Vol. IV. No. 151. 
S T R Yo 2i 7 
which drives the mercury out of the veffel, and takes its 
place. This aeriform fluid is muriatic acid gas. This 
gas is abfolutely colourlels when pure; it is fo cauftic as 
to corrode the lkin, and to caufe intolerable itching; it 
reddens the blue vegetable colours, fuch as fyrup of vio¬ 
lets and tinfture of turnfol; it deltroys animal life, and 
extinguilhes flame. It has been remarked, that the flame 
of the taper, previous to being extinguiftied, grows yel¬ 
low at the dilk towards the upper part. Fourcroy lays 
it is enlarged by the addition of a green or bluilh cir¬ 
cumambient flame, but the caufe of this is not known. 
It is obferved alfo that the flame of the taper, when go¬ 
ing out, turns very white : this is becaufe the water, 
which is difengaged by the combullion of the hydrogen 
and the oxygen of the taper, combines with the gas, and 
thus becomes cloudy and vifible. Light does not feniibly 
change it. Caloric rarefies it, and increafes its elafticity 
prodigioufly. It is heavier than atmofpherical air, in the 
proportion of 173^ to 100, and to dilliiled water as 1250 
to IOOO. 
In contaft with air, it produces white fumes or va¬ 
pours, caufed by the combination of the gas with the- 
humidity of the air; therefore thele vapours are not vi¬ 
fible on high mountains, where the air is very dry. This 
gas melts ice as quickly as if it were thrown upon live 
coals. It eafily diffolves in icy water, but not in warm 
water ; fo that it is neceffary to preferve the muriatic 
acid in water at a very low temperature ; for, if the bot¬ 
tle be not ltrong enough to refill the expanfion of the 
gas at a different temperature from that in which it was 
combined with the water, it burfts the corks, and by its 
vapour fpoils all copper utenlils. 
This gas in general unites rapidly with water, and con- 
ftitutes liquid muriatic acid. Water, at About 12 0 , ab- 
forbs o'30 of its weight; in proportion as the gas unites 
with the water, it loies its elallic fluidity; for the caloric 
which gave it this property is fet at liberty and heats the 
liquor. The lower the temperature, the more the water 
diffolves of it, and vice *uerfa \ fo that water which was 
faturated with it at 6, imbibes at fixty and forae odd de¬ 
grees, and may be deprived of the greater part of this 
acid at 8o°. 
The prefence of the muriatic acid is eafily known, 
wherever it exifts, by its property of decompofmg almoll 
all muriatic fAlts, and elpecially fulphat of filver, with 
which it forms a white precipitate, very heavy, which 
becomes blue in the light; and of giving, with foda, a 
fait of an agreeable tafte known to every one. This acid 
in general diffolves metals and oxyds in whatever ftate 
they may be; for, if they are too much oxydated, the 
muriatic acid takes away the excefs of oxygen andaffumes 
it; and, if the metal is not fufficiently oxydated, the 
water of the acid will be decompoled, and furnilh the 
neceffary oxygen ; fo that, by this reciprocal adlion, the 
oxydation is carried juft to the degree neceffary that the 
diffolution may take place. 
Muriatic acid put into a long tube with concentrated 
fulphuric acid, produces a lively effervefcence, and a. 
gas which fills the whole capacity ot the tube : this gas 
is no other than the muriatic acid, which the fulphuric 
acid has taken up from the water of iolution, and to 
which this laft has given the caloric, which it loft while 
combining with the fulphuric acid. This experiment 
proves, that fulphuric acid has more attraftion for water 
than muriatic acid. _ _ a 
Muriatic acid eafily unites with nitric, and feme inte- 
refting phenomena are produced. It the acids are con¬ 
centrated, a motion is obferved throughout all the liquid ; 
a gas comes over, which produces a brilk effervefcence ; 
the liquor heats, and affumes a red colour more or lefs 
dark. This gas is found to be oxygenated muriatic acid; 
hen mixing nitro-muriatic acid with water, it gives 
tut nitrous gas, and lofes its red colour. 
This acid is formed by the mixture of two parts of 
pure nitric acid and one of concentrated muriatic acid, 
3'K It 
