Ferro-silicon.—The illnesses due to this are phosphoretted or arseniuretted hydrogen poisoning (see pp. [191] and [197]).
Silver and Silver Compounds.—Gradual absorption of small quantities of a solution of silver may produce industrial argyria, often beginning with the appearance of a black edge to the gums and darkening of the hair and nails, followed by black spots on the skin which in severe cases coalesce, so that the whole or almost the whole surface of the body becomes black and glossy.
Argyria is due to the absorption of silver compounds into the circulation, and subsequent deposition of the reduced silver in the body (liver, kidneys, spinal cord, &c.). The black colouring of the skin is caused by the action of light.
No interference with health worth mentioning is observed.
GROUP: ARSENIC, PHOSPHORUS
The poisons (gradually absorbed) belonging to this group are mainly such as affect metabolism; they impair the processes essential to metabolism (in especial the oxidation processes) and cause severe damage to the cells, through destruction of albumen. The poisons of this group also have a paralysing effect upon the central nervous system.
Generally speaking the effects produced by the poisons of this group vary considerably. Among the arsenic compounds arseniuretted hydrogen, which is supremely a blood poison, must be excluded from the group and included among the blood poisons.
ARSENIC, OXIDES OF ARSENIC
Pure metallic arsenic (As) is considered innocuous. Oxides of arsenic especially are held to be industrial poisons such as arsenic trioxide (As₂O₃), the anhydride of arsenious acid (H₃AsO₃), a white powder, which is known under the name of white arsenic; arsenic acid (H₃AsO₄), which forms crystals easily soluble in water, and the salts of these acids, especially copper arsenite, formerly employed in the production of dyes, and also arsenic chloride (arsenic trichloride, AsCl₃). Arseniuretted hydrogen will be treated separately as it has a completely different poisonous effect from that of the oxidic compounds of arsenic. Arsenic sulphides (realgar, AsS₂, and orpiment, AsS₃) are regarded as innocuous in consequence of their insolubility in a pure state. But it may be remarked that arsenic sulphides (sulphur arsenic ores) which are used industrially, and even metallic arsenic, are to be considered poisonous, as they contain oxidic arsenic compounds in great quantity.