If arsenic, in the form of arsenious acid, were present, it would distil over as a trichloride, and be detected in the distillate; by raising the heat, the organic matter is carbonised, and most of it destroyed. The distillate is saturated with hydric sulphide, and any precipitate separated and examined. The residue in the retort will contain the fixed metals, such as zinc, copper, lead, &c. It is treated with dilute hydrochloric acid, filtered, the filtrate saturated with SH₂ and any precipitate collected. The filtrate is now treated with sufficient sodic acetate to replace the hydric chloride, again saturated with SH₂ and any precipitate collected and tested for _zinc_, _nickel_, and _cobalt_. By this treatment, viz.:-- 1. Distillation in a vacuum at a low temperature, 2. Collecting the volatile products, 3. Dehydrating the organic substances, 4. Dissolving out from the dry mass fatty matters and alkaloids, glucosides, &c., by ethereal and alcoholic solvents, 5. Destroying organic matter and searching for metals, --a very fair and complete analysis may be made from a small amount of material. The process is, however, somewhat faulty in reference to phosphorus, and also to oxalic acid and the oxalates; these poisons, if suspected, should be specially searched for in the manner to be more particularly described in the sections treating of them. In most cases, there is sufficient material to allow of division into three parts--one for organic poisons generally, one for inorganic, and a third for reserve in case of accident. When such is the case, although, for organic principles, the process of vacuum distillation just described still holds good, it will be very much the most convenient way not to use that portion for metals, but to operate on the portion reserved for the inorganic poisons as follows by destruction of the organic matter. The destruction of organic matter through simple distillation by means of pure hydrochloric acid is at least equal to that by sulphuric acid, chlorate of potash, and the carbonisation methods. The object of the chemist not being to dissolve every fragment of cellular tissue, muscle, and tendon, but simply all mineral ingredients, the less organic matter which goes into solution the better. That hydrochloric acid would fail to dissolve sulphate of baryta and sulphate of lead, and that sulphide of arsenic is also almost insoluble in the acid, is no objection to the process recommended, for it is always open to the analyst to treat the residue specially for these substances. The sulphides precipitated by hydric sulphide from an acid solution are--arsenic, antimony, tin, cadmium, lead, bismuth, mercury, copper, and silver. Those not precipitated are--iron, manganese, zinc, nickel, and cobalt. As a rule, one poison alone is present; so that if there should be a sulphide, it will belong only exceptionally to more than one metal.