N I T 
N I T 
N I T 
27<J 
with a portion of its oxygen nitrous gas and 
Oxymuriatic gas being evolved. 
It is capable of oxidizing all the metals, 
except gold, platinum, and titanium. It ap- 
pears, from the experiments of Scheffer, 
Bergman, Sage, and 'fillet, that nitric acid is 
capable of dissolving (and consequently of 
oxidizing) a very minute quantity even of 
gold. 
It even sets fire to zinc, bismuth, and tin, 
if it is poured on them in fusion, and to filings 
of iron if thevare perfectly dry. 
Nitric acid combines with alkalies, earths, 
and the oxides of metals, and forms com- 
pounds, which are called nitrats. 
The order of its affinities is as follows : 
Barytes, 
Potass, 
Soda, 
Strontian, 
Lime, 
Magnesia, 
Ammonia, 
Glucina, 
.Alumina, 
Zirconia. 
Nitric acid is one of the most important 
instruments of analysis which the chemist 
possesses ; nor is it of inferior consequence 
when considered in a political or commercial 
view, as it forms one of the most essential 
ingredients of gunpowder. Its nature and 
composition accordingly have long occupied 
the attention of philosophers ; and from their 
experiments it appears, that nitric acid is 
composed of azote and oxygen ; conse- 
quently nitrous gas is also composed of the 
same ingredients. And as nitrous gas absorbs 
oxygen, even from common air, and forms 
with it nitric acid, it is evident that nitric acid 
contains more oxygen than nitrous gas. But 
it is exceedingly difficult to ascertain the 
exact proportions of the component parts of 
this acid. Lavoisier concluded, from his ex- 
periments on the decomposition of nitre by 
charcoal, that nitric acid is composed of one 
S irt of azote and four parts of oxygen. Rut 
avy has shewn that this decomposition is 
more complicated than had been supposed ; 
and that Lavoisier’s experiments by no means 
warrant the conclusion which he drew from 
them. Cavendish, on the other hand, con- 
cluded, from his experiments, that the acid 
which he formed, by combining together 
azote and oxygen by means of electricity, is 
composed of one part of azote and 2.346 of 
oxygen. With this result the late experi- 
ments of Mr. Davy corresponded very 
nearly. He formed his standard acid by 
combining together known quantities of ni- 
trous gas and oxygen. According to him 
100 parts of pure nitric acid are composed 
of 
29.5 azote 
70.5 oxygen 
100 . 0 ; 
or 1 part of azote, and 2.39 of oxygen. 
Nitric acid is seldom in a state of absolute 
purity, holding usually a certain portion of 
nitrous gas in solution. In this state it is dis- 
tinguished by the name of nitrous acid ; a 
compound of considerable importance. See 
Nitrous Acid. 
NITRITES, are salts formed from nitrats, 
saturated with nitrous gas. See Nitrats. 
The existence of these salts was first point- 
ed out by Bergman and Scheele ; the two 
philosophers to whom we are indebted lor 
the first precise notions concerning the dif- 
ference between nitric and nitrous acids. 
They cannot be formed by combining di- 
rectly nitrous acid with the different earthy 
and alkaline bases; nor have any experi- 
ments made to combine nitrous gas with the 
nitrats been attended with success. 
The only method of obtaining these salts 
at present known, is that which was long ago 
pointed out' by Bergman and Scheele. It 
consists in exposing a nitrat to a pretty strong 
heat till a quantity of oxygen gas is disen- 
gaged from it. What remains in the retort 
after this process is a nitrite ; but the length 
of time necessary for producing this change 
has not yet been ascertained with any degree 
of precision. If the heat is applied too long 
the nitrat will be totally’ decomposed, and 
nothing but the base will remain, as happen- 
ed to some of the French chemists on at- 
tempting to repeat the process of Bergman 
and Scheele. 
Nitrite of potass is the only salt formed by 
this process, of which an account has been 
given. Scheele’s process for obtaining it is 
as follows : Fill a small retort with nitre, and 
keep it red-hot for half an hour. ' When it is 
allowed to cool it is found in the state of a 
nitrite. It deliquesces when exposed to the 
air ; and red vapours of nitrous acid are ex- 
haled when any other acid is poured upon it. 
As the nitrites have never been examined 
by chemists, and as it has not even been de- 
termined whether any considerable number 
of the nitrats can be converted into these 
salts, it would be in vain, in the present 
state of our knowledge, to attempt a parti- 
cular description of them. It may, however, 
be considered as exceedingly probable that 
no such salts as the nitrites of ammonia, glu- 
cina, yttria, alumina, and zirconia, exist or 
can lie formed, at least by the process of 
Scheele and Bergman ; for the nitrats with 
these bases are decomposed completely by 
the action of a heat too moderate to hope for 
the previous emission of oxygen gas. 
From the few observations that have been 
made, it may be concluded that the nitrites 
are in general deliquescent, very soluble in 
water, decomposible by heat as well as ni- 
trats ; that their taste is cooling like that of 
the nitrats, but more acrid and nitrous : that 
by exposure to the air they are gradually- 
converted into nitrats by absorbing oxygen ; 
but this change takes place exceedingly 
slowly. 
NITRO-MURIATIC acid. When mu- 
riatic acid is mixed with nitric acid, the mix- 
ture is nitro-muriatie acid, which was for- 
merly known by the name of aqua-regia. 
NITROUS ACID. The liquid at pre- 
sent called nitrous acid by chemists, may be 
formed by causing nitrous gas to pass through 
nitric acid. The gas is absorbed, and the 
acid assumes a yellow colour ; and its spe- 
cific gravity is diminished. It is then deno- 
minated nitrous acid. It is always in this 
state that it is obtained by distilling a mixture 
of sulphuric acid and nitre. The acid of 
commerce is always nitrous acid. The nitric 
and nitrous acids were first distinguished with 
accuracy by Scheele, 
The nature of nitrous acid was first investi- 
gated by Dr. Priestley, who demonstrated, 
by very decisive experiments, that it is a 
compound of nitric acid and nitrous gas. 
This opinion -was embraced, or rather it was 
first fully developed, by Murveau. But the 
theory of Lavoisier, which supposed the dif- 
ference between nitric and nitrous acids to 
depend merely on the first containing a 
greater proportion of oxygen than the se- 
cond, for some time drew the attention of 
chemists from the real nature of nitrous acid. 
Raymond published a dissertation in 1796, to 
demonstrate ihe truth of tlie theory of Priest- 
ley and Morveau ; and the same thing has 
been done still more lately by Messrs. Thom- 
son and Davy. At present it is allowed by 
every one, that nitrous acid is merely nitric 
acid more or less impregnated with nitrons 
gas. 
This being the case, and nitric acid being 
capable of absorbing very different propor- 
tions of nitrous gas, it is evident that there 
must be a great variety of nitrous acids, dif- 
fering from each other in the proportion of 
nitrous gas which they contain ; unless we 
choose to confine the term ni.rous acid to the 
compound formed by saturating nitric acid 
completely with nitrous gas. 
When nitrous gas is placed in contact with 
nitric acid, the acid absorbs it slowly, and 
acquires first a pale-yellow colour, then a 
bright yellow. When a considerable portion 
more of nitrous gas is absorbed, the acid be- 
comes dark orange, then olive, which in- 
creases in intensity with the gas absorbed ; 
then it becomes of a bright green; and, last- 
ly, when fully saturated, it becomes blue- 
green. Its volume and its volatility also in- 
crease with the quantity of gas absorbed ; 
and when fully saturated it assumes the form 
of a dense vapour, of an exceedingly suffo- 
cating odour, and difficultly condensible by 
water. In this state of saturation it is distin- 
guished by Dr. Priestley by the name of ni- 
trous acid vapour. It is of a dark- red colour, 
and passes through water partly without be- 
ing absorbed. The quantity of nitrous gas 
absorbed by nitric acid is very great. Dr. 
Priestley found, that a quantity of acid, equal 
in bulk to four pennyweights of water, ab- 
sorbed 130 ounce measures of gas without 
being saturated. The component parts of 
nitrous acid, of different colours and densities, 
may be seen in the following table, drawn up 
by Mr. Davy, from experiments made by 
him on purpose, with much precision : 
Component 
Parts. 
100 Parts. 
Sp. 
Grav. 
Nitric 
Acid. 
Water. 
Nitrous 
Gas. 
Solid nitric acid 
1.504 
91.55 
8.45 
. 
Yellow nitrous 
1.502 
90.5 
8.3 
2 
Bright yellow 
1.500 
88.94 
8.10 
2.95 
Dark orange 
1.480 
86.84 
7.6 
5.56 
Light olive 
1.479 
86.00 
7.55 
6.45 
Dark olive 
1.478 
85.4 
7.5 
7.1 
Bright green 
1.47G 
84.8 
7.44 
7.76 
Blue green 
1.475 
«4 6 
7.4 
8.00 
The colour of nitrous acid depends, in 
some measure, also on the proportion of wa- 
ter which it contains. When to yellow ni- 
trous acid concentrated, a fourth part by 
weight of water is added, the colour is chan- 
ged to a fine green ; and when equal parts of 
water are added, it becomes blue. Dr, 
