2. In the above process, the gas obtained, owing to the contamination of the iron sulphide, is more or less impure. When sulphuretted hydrogen is required in a state of purity, 1 oz. of antimonious sulphide must be employed instead of the iron sulphide, and instead of sulphuric 3 or 4 parts of hydrochloric acid. As heat must be applied to the mixture, it will be necessary to substitute a flask for the larger bottle, and to support it on a retort stand. In other respects the apparatus needs no alteration.
3. Sulphuretted hydrogen is also obtainable when paraffin is heated at a moderately elevated temperature with sulphur, the reaction being attended with an abundant evolution of the gas, and a simultaneous separation of carbon.
⁂ The solution of sulphuretted hydrogen, which is so indispensable to the chemist, and consequently in such constant requisition in the laboratory, unfortunately very quickly decomposes into water, and sulphur, which deposits at the bottom of the vessel containing it. To diminish as much as possible the tendency to deterioration, the solution should be made either with boiled water, or with the clear spoilt solution.
Qualities, &c. Sulphuretted hydrogen is a colourless inflammable gas, somewhat heavier than air, its specific gravity being 1·174. When ignited, it burns with a bluish flame, to water and sulphurous anhydride if the combustion take place in a sufficient quantity of air, but if the supply of air be too limited, sulphur is deposited. Under a pressure of 17 atmospheres it is condensed to a colourless and very mobile fluid, which boils at 79·6° F., and freezes at 72·8° F. to a transparent solid. Both the gas and its aqueous solution exercise a feebly acid reaction on litmus.
Sulphuretted hydrogen is highly poisonous; when inhaled in any quantity it causes fainting; and in smaller quantities, even when considerably diluted by air, if breathed for any length of time, it acts as a dangerous depressant and insiduous poison. Upon the lower animals it acts with fatal rapidity, even if diluted with 800 or 1000 parts of atmospheric air. Transmitted through tubes heated to redness, sulphuretted hydrogen becomes partially decomposed into its elements, hydrogen and sulphur. Water at 32° F. takes up 4·37 times its bulk of this gas, and at 59, 3·23
times its hulk, hence the importance of collecting it, over warm water, if required in the gaseous form.
In the presence of moisture, sulphurous anhydride and sulphuretted hydrogen, if equivalent quantities of each react upon each other, become decomposed into sulphur, water, and pentathronic acid; hence the value of sulphurous acid as a disinfectant. The deposited sulphur is found always to occur in the electro-positive condition. Chlorine, bromine, and iodine, also decompose sulphuretted hydrogen with deposition of sulphur, and formation of hydrochloric, hydrobromic, and hydriodic acids.
Hydrosulphates or Sulphides. Sulphuretted hydrogen or hydrosulphuric acid, as it is sometimes called, when brought into contact with bases in solution, gives rise to compounds, which by some chemists are regarded as hydrosulphates, or combinations of the base with hydrosulphuric acid; and by others as sulphides or combinations of the metal with sulphur, the latter reaction being attended with the elimination of water, as when a base is acted upon by hydrochloric acid. By those who hold the former view the reaction would be as follows:
K2O + H2S = K2O1H2S.
In the latter case it would be thus represented: