This acid, when pure, assumes the form of a limpid fluid, emitting white
fumes of a suffocating odour; its taste is highly acid, and corrosive;
and it is at once distinguished from all other acids, by its tinging the
skin indelibly yellow. When of the specific gravity 1·5 it contains
74·895 per cent of dry acid, (whose ultimate elements are one
proportional of nitrogen, and five of oxygen) the complement 25·105
parts, is water.[322] It is decomposed with violent action by all
combustibles, and when mixed with volatile oils it causes their
inflammation.
From the facility with which this acid undergoes decomposition, it is
rarely found in commerce in a colourless condition; indeed the action of
light is sufficient to impart a tawny tinge to it; when this change has
proceeded to such an extent as to render the acid orange coloured, it is
called _Nitrous acid_, or, in the language of the arts, _aqua fortis_,
although in a chemical point of view, such a nomenclature is incorrect,
for it is nothing more than nitric acid, holding nitrous acid gas
loosely combined.
_Symptoms of Poisoning by Nitric Acid._
This acid has been so frequently swallowed in France, for the purpose of
committing suicide, that it has enabled the pathologists of that country
to afford a very satisfactory account of its operation, and effects. To
_M. Tartra_ we are particularly indebted for a very full and interesting
investigation of the subject, and we shall avail ourselves upon the
present occasion, of the many facts and observations with which his
treatise[323] abounds. In describing the symptoms occasioned by the
ingestion of this acid, _M. Tartra_ establishes four different
gradations, viz. 1. When the death is speedy, for it is never sudden, it
commonly takes place from the _primary_ effects in about twenty-four
hours, varying from six to forty-eight hours. 2. When it proves fatal
from its _secondary_ effects, at different intervals, from fifteen days
to several years. 3. When death does not take place, but the recovery is
imperfect. 4. When a perfect cure is sooner or later obtained. The first
case is illustrated by the following example, which will serve to convey
a very just idea of the progress and intensity of the symptoms. “A man,
driven by distress to commit suicide, under the greatest agitation of
mind, and upon an empty stomach, swallowed, at a draught, two ounces of
concentrated nitric acid. Instantly he was seized with the most
excruciating pains and agitation, and could not lie in bed, but rolled
himself upon the floor. Vomiting came on, accompanied by a general
sensation of coldness, especially in the extremities. Every time he
vomited, the matter effervesced upon the pavement. A solution of soap
and oil was administered to him, and in two hours he was brought to the
hospital, often having vomited, and stopped on the road to drink. On his
arrival, he had emollient drinks, especially linseed tea, in great
abundance. He was in continual agitation, and his countenance was
greatly altered. He now vomited every instant a blackish glairy matter;
he opened his mouth easily, and his tongue was white, with a tinge of
yellow; he complained of acute pains in his mouth, along the œsophagus,
and in his stomach. His belly, slightly tense, could not bear the
slightest pressure, without great torment. The surface of the body was
cold; the pulse small and frequent; he had hiccup, and the respiration
was laborious.
His symptoms increased. He uttered sighs and lamentations; his limbs
became icy; a cold sweat covered his whole body; his pulse was scarcely
perceptible; the pain was constant; still he could rise and make
continual but useless efforts to quench his thirst, and satisfy his
urgent desire to void urine, and go to stool. He continued in this state
during the night; the matters vomited became more clear, and of a yellow
colour. He at last made a few drops of urine. The shocking appearance of
his body already resembled that of a corpse, but he retained his senses,
and was speaking when he expired, nineteen hours after swallowing the
acid.” The burning heat and pains which are commonly the immediate
effects of the ingestion of this acid are very variable in their
intensity and duration, and _M. Tartra_ observes that, in general, they
are not in proportion to the quantity or strength of the acid swallowed.
It often happens that persons who have taken only a small dose, are
seized with the most excruciating and dreadful pains, and some of those
who have swallowed a great quantity, two or three ounces for example,
have had scarcely any suffering, but remained very tranquil. In the
first case, the patients either recover, or survive a long time; in the
second, speedy death is almost always the consequence; thus a young man
of twenty died in twenty hours, without any agitation or signs of acute
pains. On opening the body, the highest degree of disorganization
appeared, perforations of the stomach, and great effusion of its
contents into the abdomen. The second variety of the progress and
termination of poisoning by nitric acid, exhibits, at first, the same
phenomena as the preceding; but less alarming symptoms succeed by
degrees; after some months, the inner membrane of the alimentary canal
detaches itself in portions, the patient falls into a marasmus, and
dies. We are here presented with a case of _consecutive_ poisoning, see
_page_ 147.
The third termination is in imperfect recovery. A slow and progressive
amendment ensures the safety of the patient; but there still remains
some complaint; obscure pains in the throat, and especially in the
epigastric region; habitual constipation, occasional vomiting, and
increased sensibility of the stomach, so that it can only support light
nourishment and bland liquors; in short, they continue invalids during
the rest of their lives; they are subject to repeated and even habitual
indispositions, and sometimes to pain and insupportable heat of the
stomach; but they are able to follow their occupations, and long survive
their poisoning.
The total disappearance of the symptoms produced by swallowing nitric
acid; or complete and absolute recovery without leaving any
consequences, is the last variety of termination.
_Organic lesions discovered on Dissection._
_Tartra_ has furnished us with the following interesting account of the
dissection of those who have died of the primary effects of nitric acid.
The external appearance of the body presents no alteration; every part
is sound and natural, and possesses, in a certain degree, the firmness
and freshness of life. The epidermis of the margins of the lips has
commonly an orange colour, more or less deep. It seems burnt and easily
separates. Sometimes yellow spots are discovered on the hands and other
parts of the body, caused by the contact of the acid. A yellow fluid, in
some cases very abundant, flows from the mouth and nostrils, and the
belly is considerably distended with air. The alimentary canal is
remarkably affected. All the internal membrane of the mouth is burnt,
and has sometimes a white colour, but is more commonly yellow; it is
separate in some places, and adheres in others. The teeth are often
loose, and have a very marked yellow colour at their _crown_. The mucous
membrane of the pharynx exhibits the same change, or is in a state of
inflammation of a dirty red colour. The whole extent of the œsophagus is
lined with a dense mass of a fine yellow colour, dry on its surface,
unctuous and greasy to the touch, and which seems to be formed both of
the mucous membrane, altered in a particular manner, and of the albumen
contained in the viscid fluid which exudes from the membrane of the
œsophagus, solidified by the nitric acid. This lining adheres in very
few points, and is easily detected from the other membranes of the
œsophagus, which are brown and blood-shot. When the stomach is not
perforated, it has commonly a considerable size; externally, its
membranes are slightly and partially inflamed, but very much towards the
pylorus and beginning of the duodenum. Its colour is faded, livid, of a
yellowish green, with large gangrenous spots. It adheres every where to
the neighbouring parts, the diaphragm, liver, spleen, and transverse
arch of the colon, by means of a concrete lymphatic exudation; its
sides, which are thin and yellow in some places, and thick and black in
others, exhibit net-work of dilated blood-vessels filled with black
coagulated blood. Often there are several points of the stomach
dissolved, and ready to burst with the slightest touch; it contains a
great quantity of gas, which has a peculiar smell, resembling that of
bitter almonds; it also very commonly contains a great quantity of
yellow matter, of a pultaceous consistence; the substance of the stomach
is generally swelled in some places, and deeply marked with black,
without being dissolved; this effect is most remarkable at the great
end, into which the acid seems to fall by its weight; the rugæ of the
stomach are very brown, and are reduced to a mucilaginous consistence.
The other parts of the alimentary canal exhibit the same organic
lesions, although the phenomena have less intensity in proportion as the
part is more distant from the stomach.
In those cases where the stomach is found perforated, its bulk is very
small; the holes commonly occur in the large and small extremities;
their form is circular, and their edges thin, and as if dissolved. The
urinary bladder contains no urine, although the patient have not
discharged any.
The appearances upon dissection of those who die of the _secondary_
effects are entirely different from those above described. It would be
difficult to find an example of greater emaciation, more advanced
consumption, or more disgusting form. Nothing is equal to the degree of
withering, and decrepitude of the whole organs; their colour is faded;
the internal cavities do not contain the usual serum; the cellular and
muscular systems are almost annihilated; the bones become dry, as in
persons of advanced age, and break with extraordinary facility; but
these changes are general and secondary, and depend upon local organic
derangement of the alimentary tube. The stomach and whole intestinal
canal are contracted to an extremely small size; the intestines are not
larger than the little finger, sometimes not exceeding a thick writing
quill; their coats are very thick, their cavity almost obliterated, and
containing only a little mucosity. The stomach, which often resembles a
portion of a small intestine, appears sound externally, and only
presents some adhesions to the neighbouring viscera; internally, the
most remarkable change is the contraction of the pylorus, the passage
through which will scarcely admit a probe; and the membranes of the
stomach itself are so thickened and compacted around it, that they have
lost all their natural suppleness. On the internal surface, there are
irregular spots, or rather smooth and red places, which seem to be
covered with a regenerated mucous membrane, less villous than that which
had been destroyed by the action of the acid; these cicatrices are
particularly large and numerous in the great end of the stomach, and
around the circumference of the pylorus.
_Chemical processes by which the presence of Nitric Acid may be
discovered._
If the acid be in any quantity, and without mixture, there cannot exist
any difficulty in demonstrating its presence. If added to copper
filings, there will be a copious disengagement of orange-coloured fumes,
and a nitrate of copper of a blue colour will remain, as the product. If
it be saturated with potass, we shall at once obtain by due evaporation
the well known substance, nitre; this salt will announce its nature by
deflagrating with charcoal or sulphur. This latter test is the one we
must employ for the detection of nitric acid, when mixed with vinegar,
and other liquids. Where the acid has combined with the animal matters
with which it may have come into contact, they must be boiled for an
hour in a solution of pure potass, when the solution will assume a
reddish appearance; this must be filtered, and evaporated in a capsule
of porcelain, when the mass so obtained will leave a residuum of nitrate
of potass.
_Dr. Marcet_, in a paper just published in the _Philosophical
Transactions_,[324] on the composition of sea water, employed a new mode
of assaying the solution for nitric acid, and for which he acknowledges
himself indebted to _Dr. Wollaston_. Having concentrated the _bittern_
in a glass vessel, until it began to deposit solid matter, he added
sulphuric acid and gold leaf, and boiled the mixture; the gold leaf was
not in the least acted upon, nor was any smell of nitric acid perceived;
but on adding the smallest quantity of nitre to the same mixture, the
gold was dissolved, and the smell of _aqua regia_ instantly perceived.
The rationale of the experiment is obvious, gold, although insoluble in
muriatic acid, is instantly dissolved on the addition of nitric acid, in
consequence of the developement of chlorine.