This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Phosphorus itself, unchanged, is probably quite inert Its entire insolubility, the perfect impunity with which it can be handled, and its want of taste when quite clean, are evidences to this effect Its whole influence probably depends on changes which it undergoes in the stomach, or in the blood after absorption.* In relation to its direct influence on the gastric mucous membrane, it may be supposed to produce its simple excitant effect through some one of the acids resulting from its oxidation, and. when it is taken very much divided in solution, the probability is that it is mainly the phosphorous acid which is produced, and which acts. This is of course conjectural; for we do not know the precise effects of that acid when given in substance. It may be that the heat evolved by the slow oxidation of the phosphorus may have some effect in producing the excitation of the mucous membrane. But, in relation to its violent and poisonous action on the stomach, to the high inflammation, corrosion, and gangrene which have sometimes resulted, I am among those who ascribe them to the active combustion of the phosphorus. + This takes fire at 100°, and the heat of the stomach probably is equal to that degree or above it. Atmospheric air is often contained in the organ. These then are the two requisites for combustion; and it is probable, whenever phosphorus is swallowed in the solid state, and comes into contact with the air, that it takes fire. Thus we can explain why it is that, when serious accidents have occurred, it has generally been from phosphorus taken undissolved. Hence too the great uncertainty in its poisonous effects. It may be readily understood that a grain, or even a small fraction of a grain, taking fire in contact with the surface of the stomach, may produce fatal disorganization; while sixteen grains may be swallowed with impunity, if shielded from the air, or if no air is present.
The effects on the system are almost certainly the result of absorption. That in one form or another the phosphorus enters the circulation, is proved by the alliaceous odour of the breath, and, as has been asserted, of the blood. It is probably in the state partly of phosphorous acid, and partly of phosphoric acid, that it is taken up. The odour of the breath would seem to indicate the former, the excess of phosphates in the urine the latter. It is not impossible that the phosphorus itself, in the state of solution, or in that of vapour (see note, p. 571), is also absorbed; and the fact must be admitted, if it is true that the urine sometimes becomes phosphorescent under its use.* It is not impossible that the poisonous effects of the absorbed phosphorus may be owing to its combustion in the blood. This supposition is favoured by the fact that phosphoric acid, given to dogs in much larger doses than that in which phosphorus proves fatal, has evinced no poisonous effect. (T. B. Groves, Pharm. Journ. and Trans., xvii. 510).
* Recent experiments by M. Blondlot prove that phosphorus slowly rises in vapour at 104° F.; and us this is but little above the ordinary interior temperature of the body, it is not improbable that the phosphorus may be volatilized in the stomach, and that it is really in the state of vapour that it is absorbed. (Journ. de Pharm. et de Chim., Nov. 1866, p. 323.) - Note to the third edition.
+ Strongly confirmatory of this opinion is the fact, ascertained by Orfila and Ri-gaut through experiments on dogs, that phosphorus, in the allotropic state denominated red phosphorus, is wholly destitute of poisonous properties. (Ann. de Therap., 1857, p. 284.) Now this variety of phosphorus does not undergo combustion at ordinary temperatures, and consequently will not take fire in the stomach. It is true that its want of poisonous properties may be ascribed to the non-production of phosphorous acid by its oxidation. But it has been ascertained that it really does undergo a slow oxidation at. ordinary temperatures. (Jahresbericht, 1857, v. 46.) Consequently its harmlessness is fairly ascribable to its incombustibility. (Note to the second edition).
If phosphorus should have been taken in dangerous quantities, it should be immediately evacuated by an emetic, with copious draughts of mucilaginous drinks to envelop the poison, and keep it as much as possible from the action of air in the stomach; magnesia being at the same time given to neutralize any acid which may have resulted from its oxidation. Should symptoms of inflammation or corrosion remain after the evacuation of the poison, they must be combated by the ordinary methods, such as leeches followed by emollient cataplasms to the epigastrium, mucilaginous drinks, or opiate enemata; while one of the alkaline bicarbonates may still be exhibited to neutralize any acid that might remain. It has occurred to me that, should a piece of solid phosphorus be swallowed, the free use of carbonic acid water, with bicarbonate of soda in solution, might be useful until the poison could be evacuated. The carbonic acid evolved from the liquid by the heat of the stomach would fill its cavity with a gas, which not only does not support combustion, but, mingled largely with atmospheric air, suppresses the supporting power of it also; while the alkaline bicarbonate would neutralize any free acid present, and still further increase the atmosphere of the acid gas. It has been recommended to wash the burns produced by inflamed phosphorus on the surface with an alkaline solution, in order to remove the phosphoric acid.