CHAPTER VIII.
OF POISONING WITH NITRATE OF POTASS.
The nitrate of potass [nitre, saltpetre, sal-prunelle], is a dangerous poison. It has been often mistaken for the saline laxatives, especially the sulphate of soda, and has thus been the source of fatal accidents.
Section I.—Of the Chemical Tests for Nitrate of Potass.
It exists in commerce and the arts in two forms, fused and crystallized. The fused nitre [sal-prunelle] is sold in little button-shaped masses, spheres of the size of musket-balls, or larger circular cakes, of a snow-white tint. The crystallized salt [sal-petre] is sold in whitish, sulcated crystals, which are often regular and large. They are six-sided prisms, more or lest flattened, and terminated by two converging planes. In both forms nitre has a peculiar, cool, but sharp taste.
Its chemical properties are characteristic. In the solid form, it animates the combustion of burning fuel, and yields nitrous fumes when heated with strong sulphuric acid. In solution it is precipitated yellow by the chloride of platinum, and yields, when not greatly diluted, a crystalline precipitate with perchloric acid. The crude salt of commerce contains chloride of sodium; and hence the odour disengaged by sulphuric acid may be mixed with that of chlorine or hydrochloric acid gas. When mixed with any vegetable or animal infusion by which it is coloured, crystals may sometimes be easily procured in a state of sufficient purity by filtration and evaporation. But if not, then the same process must be resorted to with that formerly recommended for nitric acid (p. [143]), the first step of neutralization with potass being of course dispensed with.—A process nearly the same with this has been suggested by M. Kramer of Milan. He proposes to free the liquid in part of animal matter by adding acetate of lead, transmitting sulphuretted-hydrogen through the filtered fluid to remove any excess of lead, boiling the fluid after another filtration, and then proceeding with acetate of silver to remove chlorides, as in the process I have adopted. In this way he found nitre even in the blood.[[447]]
Section II.—Of the Action of Nitrate of Potass and its Symptoms in Man.
This substance forms an exception to the general law formerly laid down with regard to the effect of chemical neutralization on the local irritants. Both its acid and its alkali are simple irritants; yet the compound salt, though certainly much inferior in power, is still energetic. Nay, the experiment of Orfila and the particulars of some recently published cases tend even to prove, that the action of its alkali and acid is materially altered in kind by their combination with one another; for, besides inflaming the part to which it is applied, nitre has at times produced symptoms of a secondary disorder of the brain and nerves.
The experiments of Orfila upon dogs show that on these animals it has a twofold action, the one irritating, the other narcotic. He found that an ounce and a half killed a dog in ninety minutes when the gullet was tied, and a drachm another in twenty-nine hours: that death was preceded by giddiness, slight convulsions, dilated pupil, insensibility and palsy; that after death the stomach was externally livid, internally reddish-black, and the heart filled in its left cavities with florid blood; that when the gullet was not tied the animals recovered after several attacks of vomiting, and general indisposition for twenty-four hours; and that when the salt was applied externally to a wound it excited violent inflammation, passing on to gangrene, but without any symptom which indicated a remote or indirect operation.[[448]] Mr. Blake found that this salt, when injected into the veins of a dog in the dose of fifteen grains dissolved in twenty-four parts of water, causes sudden depression and arrestment of the action of the heart, and death in less than a minute; but that, like other salts of potash, it has no influence on the capillaries of the lungs, though a powerful effect in obstructing the systemic capillary system.[[449]]—When taken in the ordinary way, it is absorbed in the course of its action, and has been detected both in the blood and the urine by Kramer of Milan.[[450]]
As to its effects on man, it must first be observed, that considerable doses are necessary to cause serious mischief. In the quantity of one, two, or three scruples, it is given medicinally several times a day without injury; and Dr. Alexander found by experiments on himself, that an ounce and a half, if largely diluted, might thus be safely administered in the course of twenty-four hours.[[451]] Sometimes, too, even large single doses have been swallowed with impunity. A gentleman of my acquaintance once took nearly an ounce by mistake for Glauber’s salt, and retained it above a quarter of an hour: nevertheless, except several attacks of vomiting, no unpleasant symptom was induced. M. Tourtelle has even related an instance where two ounces were retained altogether and caused only moderate griping, with considerable purging and flow of urine.[[452]] Resting on such facts as these Tourtelle, with some physicians in more recent times,[[453]] has maintained that nitre is not a worse poison than other saline laxatives; and some practitioners of the present day have consequently ventured to administer it for the cure of diseases, in the quantity of half an ounce in one dose.[[454]] It is not easy to say, why these large doses are at times borne by the stomach without injury,—whether the cause is idiosyncrasy, or a constitutional insensibility engendered by disease, or some difference in the mode of administering the salt. But at all events, the facts which follow will leave no doubt that in general it is a dangerous and rapid poison in the dose of an ounce.
Dr. Alexander found that, in the quantity of a drachm or a drachm and a half, recently dissolved in four ounces of water, and repeated every ninety minutes, the third or fourth dose caused chilliness and stinging pains in the stomach and over the whole body; and these sensations became so severe with the fourth dose, that he considered it unsafe to attempt a fifth.[[455]]