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 poisons, that notwithstanding their extensive use in the arts, well-observed instances of poisoning by means of a bichromate are rare. Dr. Cloet, who made a careful investigation into the condition of health of the people engaged in a bichromate manufactory, states that, taken internally, it is not poisonous in such minute doses as cyanide of potassium, about fifteen grains being necessary to cause death in a healthy adult person; but it is in coming in contact with the mucous membrane, or with a slight abrasion of the skin, that its most injurious action is found,—obstinate and dangerous ulcerations, issuing occasionally in complete destruction of the part, ensuing. It is observed that when used with care, no danger whatever need be apprehended, as it is quite innocuous on the skin when there is no abrasion; no absorption of the poison taking place, except by the mucous membrane, or through a wound of some kind. The important point for photographers to observe is, to avoid contact with the bichromate where there is any scratch or lesion of the skin, and to avoid contact with the eyes or nostrils with fingers which have recently touched the chromic salt. Dr. Cloet says:

“This salt (bichromate of potash) in small doses, say a few grains, acts as a purgative; if in larger doses, say fifteen grains, it acts as a poison. A workman in a factory put some bichromate into a barrel of cider, by way of joke. The cider was rendered dark in color, but still the other workmen drank of it, and were all affected with severe colic and diarrhœa. Disease of the nostril has been produced by workmen who, having stained their fingers with the salt, have put them into the nostril.

“In transforming neutral chromate of potassa into bichromate, by means of acid, the vapor arising carries with it an infinity of pulverulent molecules of the product, which spread through the workshop. This cloud of particles is easily visible in a ray of sunlight. The molecules inspired give a bitter and very disagreeable taste to the palate; but as profuse salivation is the result, the