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 directed above, and then proceed as with the liquid portion of the urine.

Some other processes, but probably inferior to that of Professor Orfila, will be found in the last edition of this work. It seems unnecessary to reproduce them here.

6. Of Bicyanide of Mercury.

The bicyanide of mercury is a compound of mercury and cyanogen. It is usually sold in the form of white, opaque, heavy, crystals, which are rhomboidal prisms. It has a disagreeable, corrosive, metallic taste. It is easily known from every other substance by the effects of heat. If a small quantity of it, previously well dried, be introduced into a glass phial to which a small tube is fitted by means of a cork, on the application of heat the salt becomes black; mercury is sublimed, and condenses in globules on the upper part of the phial; and a gas escapes, which has the odour of prussic acid, and burns with a beautiful rose-red flame.

7. Of the Nitrates of Mercury.

The nitrates of mercury are used in some of the arts, but have so rarely been the cause of injury to man that they are of little medico-legal importance. I am acquainted with only one case of poisoning with them.

There are two nitrates, the protonitrate and pernitrate. 1. The protonitrate is in transparent colourless crystals, entirely soluble in water with the aid of a slight excess of nitric acid; and the solution is precipitated black by the alkalis, black by sulphuretted-hydrogen, white by muriatic acid, and yellow by hydriodate of potass. The crystals when heated discharge fumes of nitrous acid, and when the whole acid is driven off the red oxide is left, which by farther heat is converted into metallic mercury. 2. The pernitrate is similarly affected by heat. Its crystals form white or yellowish needles. Water decomposes them, separating an insoluble yellowish subnitrate, and dissolving a supernitrate, which is precipitated yellow by the alkalis, black by sulphuretted-hydrogen, carmine-red by the hydriodate of potass. Copper separates mercury from both nitrates; and so does gold or platinum when aided by a galvanic current.

—Of the mode of Action of Mercury and the Symptoms it excites in Man.

The effects of mercury on the animal body are more diversified than those of any other poison. It acts on a great number of important organs, and in consequence the phenomena of its action are proportionately various. It is not surprising, therefore, that some