This metal does not exert any influence on the living body; but its
oxide in combination with nitric acid constitutes one of the most
corrosive of all the metallic salts.
LUNAR CAUSTIC. _Nitrate of Silver._
_Lapis Infernalis._
The usual state in which this substance occurs is in that of small
cylinders, having been cast into moulds for the purpose of imparting to
it a form best adapted for the purposes it is designed to answer.
Its action on animal matter is highly caustic, and when introduced in
any considerable quantity into the stomach, will induce death by
corroding the texture with which it may come in contact. At the same
time there is reason to believe that the whole, or part of its
composition, may be absorbed; for we have many instances on record where
the frequent repetition of this metallic salt, in small doses, has
imparted a blue tinge to the skin, which can only be explained on the
supposition that the oxide of the metal has been actually deposited in
the rete mucosum[319].
We are not aware that there is any modern case of poisoning by this
salt[320]. The medical practitioner, however, ought to know, that common
salt, is its true antidote; indeed so completely does it decompose and
separate it from water, that if a saturated solution of nitrate of
silver be filtered through common salt, it may be afterwards drunk with
impunity. _M. Orfila_, by a series of experiments, has shewn that if the
_muriate of soda_ be administered a very short time after the ingestion
of lunar caustic, it will disarm it of its virulence by transforming it
into an insoluble muriate, possessing no power of acting on the animal
œconomy.
_Chemical processes for the detection of Lunar Caustic._
If a small portion of the salt can be procured it may be dissolved in
distilled water, and immediately identified by the following tests.
_a._ _Muriatic acid, or any soluble Muriate_, will precipitate the
muriate of silver, which is white, curdled, very heavy, insoluble in
water, or nitric acid; but soluble in liquor ammoniæ; when exposed to
the air it acquires a black colour.
_b._ _Potass_, _Soda_, and _Lime water_, will occasion a precipitate of
the oxide, of a deep brown colour.
_c._ _Ammonia._ This alkali will form an _ammoniuret of silver_, and in
consequence of the solubility of this new product, little or no
disturbance is occasioned by the test.
_d._ _Arsenite of Potass._ As all re-agents must be considered as
reciprocal in their operation, it is hardly necessary to state that this
is one of the best tests for nitrate of silver. See the history of its
effects at p. 240.
If it should be necessary to discover the nitrate of silver amongst the
fluids vomited, or those contained in the stomach of the deceased, we
are very properly directed by _M. Orfila_ to filter, and then assay by
the appropriate tests; if, however, the different aliments should
disguise the characteristic colour and appearance of these precipitates,
we must proceed to desiccate and calcine them in order to obtain the
silver in a metallic state.