SALT AS A CHEMICAL, THERAPEUTICAL, AND TOXICOLOGICAL AGENT.
As a chemical agent, and from the manufacturing uses to which it is now
put, salt is a most invaluable article from a scientific as well as
from a commercial point of view. I will therefore draw the attention
of my reader to its chemical properties; I will then allude to a few
drugs which are partially derived from salt or the chloride of sodium;
and will cursorily notice one great staple of commerce which owes the
rapidity of manufacture to its sole agency, including some remarks on
it as a poison.
_Chlorine_ gas, which is obtained from the _chloride of sodium_, was
discovered by Scheele in 1777, who named it _dephlogisticated muriatic
acid_. Berthollet in 1785 termed it _oxygenated muriatic acid_. Sir
Humphry Davy called it _chlorine_ (from χλωρὸς, green) on account of
its colour, and it has kept this name ever since. We thus see that salt
is of great use to the chemist, for he not only obtains _chlorine_ gas
from it, but also _hydrochloric acid_, a most useful and efficacious
drug in the treatment of some hepatic diseases. _Chlorine_ also enters
into combination with other chemical substances known as _chlorides_
and _chlorates_, _sub-chlorides_ and _per-chlorides_; for instance, we
have the _chloride of ammonium_ and the _chlorate of potash_; we also
have the _sub-chloride of mercury_, or _calomel_, and the _perchloride
of mercury_, or _corrosive sublimate_, with various others.
According to Pereira, _hydrochloric acid_ was known to Djafar, or
Geber, an Arabian chemist who flourished in the eighth century, and
whom Roger Bacon calls _magister magistrorum_. Everyone is acquainted
with the _chloride of lime_, a substance so generally used for
household and disinfecting purposes, that I need only mention it;
besides this, there are other salts with which _chlorine_ enters into
combination.
Formerly, to bleach cotton it was required to expose the material to
the action of the sun and air, rendering the process long and tedious,
as it took on the average quite six or eight months, and likewise a
large surface of land was necessary for the operation.
Now, owing to _chlorine_ gas, the process is completed in a few hours,
and a comparatively small building is quite sufficient for the purpose;
the fibre is beautifully and permanently whitened, and the manufacturer
experiences the pleasing satisfaction of a more rapid remuneration.
Where would be our delicately white textile fibres were it not for the
abundant and inexhaustible supply of salt? How should we be enabled
to cause vegetable colours to vanish as if touched by the hand of a
magician were it not for the bleaching properties of _chlorine_? And
how should we be able to procure this green-coloured gas which produces
these changes were it not for the _chloride of sodium_?
As a therapeutical agent _chlorine_ possesses some characteristics
peculiar to itself: it is used as a lotion for cancerous growths and
foul ulcers, also for some cutaneous eruptions. It is likewise used
as a vapour-bath; it has also been used in the treatment of chronic
bronchitis and phthisis, and as a gargle in certain morbid conditions
of the mouth. When _chlorine_ is absorbed by the system it is supposed
to possess some antiseptic and alterative action, acting specifically
on the liver.
There is one more fact of a chemical nature in reference to chlorine
which it would be unwise to throw aside, as it possesses some degree of
interest. When the chemist wishes to decompose water, or in other words
to liberate hydrogen from oxygen, he has no better agent to effect
the purpose than this greenish-coloured gas, because it has such a
strong affinity for _hydrogen_, which is one of the most characteristic
properties of _chlorine_. Mix them together, and they combine with
explosive violence if they are exposed to the beams of the sun. By
this process we obtain _hydrochloric acid_ gas, while the _oxygen_ is
liberated.
_Chlorine_ only becomes active when it is associated with moisture;
when dry it is quite inert as regards its bleaching powers, for “when
moist it gradually decomposes the water, combining with its _hydrogen_,
and disengaging its _oxygen_; and it is this _oxygen_, at the moment of
its liberation, which is the really active agent in bleaching.”[28]
Salt, like other inorganic compounds, has been known to act as a poison
when taken in a large quantity, and Dr. Alfred Taylor, the eminent
toxicologist, mentions a case in which a table-spoonful was taken by
mistake for sugar; there was no vomiting or purging, but great pain in
the region of the stomach, with dryness of the fauces, which lasted
several days. Did not the above emanate from so great an authority,
one would feel inclined to question it. Could anyone take such a large
amount and swallow the same without being immediately aware of his
mistake? Surely he would have immediately and spasmodically ejected
it by reason of its extremely pungent character, before it had even
reached the fauces.
Dr. Taylor says that “in a toxicological view it is not easy to
distinguish the effects of common salt in these cases from the
poisonous action of salt of sorrel, or binoxalate of potash, which
it is well known may be taken with impunity in small quantity;” the
symptoms are those of irritant poisoning, causing great pain and
intensely inflaming the stomach and intestines, and in those few cases
which we have on record the vomiting was excessive.
In France, though not hitherto, as far as I am aware, in Great Britain,
several instances have occurred of severe sickness in particular
localities, which have been traced to the adulteration of common salt
with certain deleterious articles. In an investigation conducted by
M. Guibourt some years ago, in consequence of some severe accidents
which were presumed to have been produced apparently by salt in Paris
and at Meaux, oxide of arsenic was detected; and this discovery was
corroborated by MM. Latour and Lefrançois, who ascertained that
the proportion of arsenic was sometimes a quarter of a grain per
ounce. Another peculiar adulteration which was frequent was with the
hydriodate of soda. At a meeting of the Parisian Academy of Medicine,
held in December, 1829, an interesting report was read by MM. Boullay
and Delens, subsequent to the inquiry by M. Sérullas, into the nature
of a sample of salt which occasioned very extensive ravages. In the
year 1829 various epidemic illnesses in several parishes were supposed
to have originated from salt of bad quality, and in one month no less
than 150 people in two parishes were attacked, some with nausea and
pain in the stomach, slimy and bloody purging, some with tension of
the abdomen, puffiness of the face, inflammation of the eyes, and
œdema of the legs; and in some districts of the Marne one-sixth part
of the inhabitants were affected in a similar manner. The salt being
suspected, as it had an unusual odour somewhat like the effluvia of
marsh land, it was analysed by M. Sérullas, and after him by MM.
Boullay and Delens; the experiments of all three indicated the presence
of one hundredth of its weight of hydriodate of soda, besides a small
amount of free iodine. Owing to the discovery of arsenic by other
experts in different samples of suspected salt, M. Sérullas repeated
the analysis, but was unable to detect the slightest trace of that
poison.
“M. Barruel states that he observed the occasional adulteration of salt
with some hydriodate accidentally in 1824, while preparing experiments
for Professor Orfila’s lectures. He also found it in two samples from
different grocers’ shops in Paris. No satisfactory explanation has yet
been given of the source of the adulteration with arsenic; but the
presence of the hydriodate of soda has been traced to the fraudulent
use of impure salt from kelp.”[29]
It will be as well for us to know what pure salt really consists of, to
the composition of which I now draw the reader’s attention:
COMPOSITION OF THE PURE CHLORIDE OF SODIUM.
Atoms. Eq. wt. Per cent. Ure. Longchamps.
Sodium 1 23 39·3 39·98 39·767
Chlorine 1 35·5 60·7 60·02 60·233
— ———— —————— —————— ———————
2 58·5 100·0 100·00 100·000
MM. St. Claire Deville and Fouqué have shown that common salt can be
resolved into its elements by the action of hot steam alone, which
Lussa and other chemists had thought impossible.
Prof. Meyer, of Berne, has lately demonstrated by experiments on
chlorine gas, that the assumption of its elementary character is an
error, and that it is nothing more or less than the oxide of a metal
which he calls _murium_. This discovery opens up an interesting
question for physiological chemists to investigate; for if he is
correct, chlorine is not an element, but is simply the oxide of a
metal.