of the metal may be obtained, by drying it upon a filter, mixing it with an equal bulk of potass, and melting it in a small glass tube. This complicated mode of proceeding will rarely be found necessary; but it should not be neglected, where the presence of arsenic cannot be otherwise detected in the alimentary canal of those who are suspected to have died from its ingestion, especially in the examination of a body where, from the length of time it may have been under ground, there is reason to suppose that the acid exists in a state of intimate combination with the animal matter. And we may take this opportunity to observe, that advanced putrefaction, however disagreeable it may render such researches, will not, in the case of arsenic, defeat their success; let the forensic physician, then, remember, that the length of time which may have elapsed since the death of the body, ought never to be urged as a plea for not having proceeded in its dissection. The task may be personally disagreeable, but it will be less painful than the reflections which must attend a breach of duty; upon such an occasion we would address the anatomist in the quaint but expressive words of _Teichmeyer_[262], “_Præstat enim manus quam conscientiam cruentare et contaminare._” ARSENIC ACID, and ITS SALTS. It has been stated, that the Metal Arsenic is susceptible of two degrees of oxidizement, the result of its first degree being Arseni_ous_ acid, and that of its second Arsen_ic_ acid. This latter compound, of which we are now to treat, may be obtained by the repeated distillation of white arsenic with nitric acid. In a solid state it is white, not crystallizable; of a sour, and at the same time, metallic taste; its specific gravity is 3·391; when exposed to the action of heat in a close vessel, it does not become volatile, but melts and vitrifies; thrown on burning coals, it swells, parts with its water, and becomes opaque; if the process of deoxidation be continued, it will, at length, rise in vapours, like those of arsenious acid, and which, like them, will yield an alliaceous odour, or not, according to the circumstances already explained. The _Arsenic acid_ dissolves very readily in water, and is even indeed deliquescent. With alkalies, earths, and oxides, it constitutes a class of salts, called “_Arseniates_,” all of which, as well as the pure acid, are extremely active poisons; fortunately, however, they are not much employed[263] in this country, and are not likely to become the instruments of crime. These salts, like those of the arsenious acid, are obedient to the different re-agents which were enumerated under the consideration of this latter substance, but with different results; thus the _silver_ test, instead of producing the yellow indication, occasions an equally characteristic precipitate of a red, or brick colour. The ammoniuret, and acetate of copper, furnish a bluish-white precipitate. The arsenic acid, in a solid form, or the