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 dead about twelve hours afterwards, without any sign of vomiting, purging, or convulsions; and no morbid appearance was found but redness of the villous coat of the stomach, and an inky-like fluid in it, containing a large quantity of bichromate of potash.

To these facts may be added another not less singular, which my late colleague Dr. Duncan informed me has been observed by the workmen in Glasgow, who use the bi-chromate of potass in dyeing. When this salt was first introduced into the art of dyeing, the workmen who had their hands often immersed in its solution were attacked with troublesome sores on the parts touched by it; and the sores gradually extended deeper and deeper, without spreading, till they sometimes actually made their way through the arm or hand altogether.

Of Poisoning with Zinc.

The compounds of zinc, which have been long used in considerable doses in medicine, have sometimes occasioned serious and even fatal effects. Partly on this account, and partly because one of them, the sulphate of zinc, being the emetic most commonly used in the treatment of poisoning, is apt to complicate various medico-legal analyses, it will be proper to notice both its physiological properties and the mode of detecting it by chemical means.

The only important compound of this metal is the sulphate or white vitriol. As usually sold in the shops, it forms small, prismatic crystals, transparent, colourless, of a very styptic metallic taste, and exceedingly soluble in water. That which is kept by the apothecary is tolerably pure; but there is a salt sometimes met with in commerce which contains an admixture of sulphate of iron, and with which the natural action of the tests for zinc is materially modified.

The solution of the pure salt is precipitated white by the ''caustic alkalis'', an oxide being thrown down, which is soluble in an excess of ammonia. The alkaline carbonates also precipitate it white, the carbonate of ammonia being the most delicate of these reagents. The precipitate is soluble in an excess of carbonate of ammonia, and is not thrown down again by boiling. The precipitate produced both by the alkalis and by their carbonates becomes yellow, when heated nearly to redness; and on cooling it becomes again white. This is a characteristic property, by which the oxide of zinc may be known from most white powders. But oxide of antimony is similarly affected. The ferro-cyanate of potass also causes a white precipitate. A stream of sulphuretted-hydrogen likewise causes a white precipitate, the sulphuret of zinc, the colour of which distinguishes the present genus of poisons from all those previously mentioned, as well as from the poisons of lead. The precipitate is apt to be suspended till the excess of gas is expelled by ebullition. The action of this test will not distinguish sulphate of zinc from the salts of peroxide of iron, by which white sulphur is disengaged from the gas in consequence of