SULPHURETTED HYDROGEN

Hydro-sulphuric Acid. A gaseous compound of 1 atom of sulphur = 16 + 1 atom of hydrogen = 1. The equivalent, therefore, of sulphuretted "hydrogen is 17. This gas was first examined by Scheele in 1777. It may be obtained by acting upon sulphuret of antimony by muriatic acid, or upon pro to sulphuret of iron by diluted sulphuric acid, and is immediately recognised by its peculiar fetid odour, which is so diffusible that a single cubic inch of it escaping into the atmosphere of a large room is soon everywhere perceptible by its smell. It is very deleterious to respiration. 100 cubic inches weigh about 36 grains, its specific gravity compared with air being as 1180 to 1000, or, compared with hydrogen, as 17 to 1. It is liquefied by a pre ure of 17 atmospheres at 50°. Water agitated with this gas takes up its own volume, and acquires a bitterish nauseous flavour, and the odour which characterizes Harrow gate and Aix-la-Chapelle waters, a^id which derive their chief peculiarities from the presence of this gas. Sulphuretted hydrogen extinguishes flame, but is itself inflammable in the contact of air, burning with a blue flame, and depositing, during its slow combustion,a portion of its sulphur. When mixed with exce of oxygen and inflamed, it explodes, and the mixture is converted into sulphurous acid and water. One volume of the gas requires one volume and a half of oxygen for its entire combustion, and the results are water, and 1 volume of gaseous sulphurous acid. This gas is immediately decomposed by chlorine and by iodine, which, if not added to exce , throw down its sulphur and combine with its hydrogen.Itis unequivocally recognised by its peculiar odour, and by its blackening the salts of lead. Sulphuretted hydrogen, diluted with 20,000 measures of pure hydrogen, sensibly blackens a piece of paper which has been dipped into a solution of acetate of lead: white lead is also immediately discoloured by it; hence the mischief which it does to white paint, and to pictures. The aqueous solution of sulphuretted hydrogen reddens litmus; and inasmuch as it combines with certain bases, it is properly considered as a weak acid. SULPHURIC ACID, Oil of Vitrioh This most important acid was discovered by Basil Valentine towards the end of the 15th century. It was formerly obtained by the distillation of green vitriol, and from its oily appearance it acquired the name, which it still bears, of oil of vitriol. In this country it is procured by burning a mixture of 7 or 8 parts of sulphur with 1 of nitrate of soda or of potash. The mixture is burned in a furnace so contrived that a current of air carries the products of the combustion into a large leaden chamber, the bottom of, which is covered to the depth of a few inches with water. The principle products of the combustion of the above-mentioned mixture of nitre and sulphur are sulphurous and nitrous acids; and these, together with atmospheric air and aqueous vapour, form the contents of the chamber. The sulphurous and nitrous acids, with a portion of water, combine to form a white crystalline substance, which, upon falling into the water of the chamber, is instantly decomposed.The nitrous acid imparts oxygen to the humid sulphurous acid, and so converts it into sulphuric acid; while the nitrous acid, having lost oxygen, reverts to the state of nitric oxide, which is given out into the air of the chamber, from which it immediately again abstracts oxygen, and becoming nitrous acid, is again ready to acidify a new portion of sulphurous acid. The oxygen, therefore, is thus indirectly transferred to the sulphur, or to the sulphurous acid, from the atmosphere, through the medium of the attractive power of the nitric oxide for that element; and the circumstance of this proce being repeated over and over again by the same portion of nitrous gas, accounts for the small quantity of nitre required in this curious proce . When the water in the chambers is rendered sufficiently acid, which is judged of by its specific gravity, it is drawn off" into leaden boilers, where it is evaporated down to a certain density; after which, as it would then act upon the lead, it is transferred to platinum boilers supplied with still heads, and there is brought to its proper degree of concentration by farther distilling off" a portion of the residuary water. This last proce was formerly conducted, at great 1300 [s. 1214]