4. The acid liquid, saturated with carbonate of potash and evaporated, deposits _fluted_ prisms which do not effloresce or deliquesce on exposure. Neutralised with soda, the crystals are of a _rhombic_ form. 5. A crystal, so formed, moistened with distilled water on a plate, and then heated with strong sulphuric acid and allowed to cool, gives with-- (1) A piece of _green sulphate of iron_--a dark green ring round the crystal. (2) A small portion of _morphia_--a rich orange colour, a yellow liquid being formed. (3) A small portion of _brucine_--a blood-red colour. 6. If an aqueous solution of diphenylamine be added to a solution containing nitric acid, in a test tube, and pure sulphuric acid be poured down the side of the tube to form a layer at the bottom, a blue colour forms at the junction of the two liquids. III. Mixed with Organic Liquids, &c. Due to the measures employed by way of treatment the vomited matters may be neutral and yet nitric acid be present. The method adopted with viscid and turbid organic mixtures is to dilute them with pure water, and then filter. If the filtrate be acid, it is neutralised with carbonate of potash, evaporated, and then set aside to crystallise, and the crystals purified by digesting them in ether or alcohol. The crystals are again dissolved and re-crystallised. The tests just mentioned should then be employed. It should be remembered that nitric acid has a strong tendency to combine with solid organic structures, and to become decomposed. The parts of the body stained by the acid should, therefore, be digested in water at a gentle heat, the liquid cooled, filtered, and neutralised with carbonate of potash, and then examined for nitre. IV. Stains on the Clothes, &c. Macerate the piece of cloth in distilled water by the aid of heat. If the solution be acid, neutralise with carbonate of potash, and filter. Test the solution as before mentioned. The action of the dilute solution of caustic potash on the following stains on cloth is characteristic: Nitric acid stain becomes of a clear orange tint. Iodine stain disappears. Bile stain remains unchanged. _Fatal Period._--Death may take place in an hour and a half, or life may be prolonged for some months. _Fatal Dose._--Two drachms; recovery has taken place after half a fluid ounce of the strong acid has been taken. _Treatment._--As before mentioned when speaking of the acids generally. HYDROCHLORIC ACID _Forms._--Strong and the dilute acid. It is known as muriatic acid, or spirits of salts. _Characters._--_Strong hydrochloric acid_ is either colourless or has a bright yellow tint, due to the presence of the perchloride of iron. It fumes in the air, and gives rise to dense white fumes when a glass rod moistened with ammonia is held over the surface of the acid. The _dilute acid_ is colourless.