4053. To Obtain Sulphuretted Hydrogen

4053.      To Obtain Sulphuretted Hydrogen. Mix together 2 parts of iron filings with 1 of sulphur into a thin pap with water, and heat it gently in an iron vessel. Combination takes place with the evolution of heat forming sulphuret of iron. Cover it till cold. On this compound, contained in a glass bottle, or other suitable apparatus, pour sulphuric acid previously diluted with 7 parts of water. If more acid bo afterwards required, dilute the strong acid with only 4 of water. The resulting gas is absorbed by water, and is therefore collected, in preference, over mercury. This is the plan commonly adopted in the laboratory.

To obtain it pure, mix 1 part finely powdered tersulphuret of antimony, anil 5 parts strong muriatic acid, in a small glass retort or flask : apply the heat of a spirit lamp, and collect the gas over mercury. (See No. 4031 (Pneumatic Trough).)

4054. Tests for Sulphuretted Hydrogen

4054.     Tests for Sulphuretted Hydrogen. Sulphuretted hydrogen may be recognized by the odor, and by its blackening moist carbonate of lead, and. tarnishing silver, and also by its precipitating arsenious acid, yellow, tartar emetic orange, and the salts of lead black.

4055. Phosphuretted Hydrogen

4055.   Phosphuretted Hydrogen. This is a gaseous combination of phosphorus and hydrogen; colorless, very fetid, slightly soluble in water, and burns with a white flame. It has a specific gravity of 1.24.

4056. To Obtain Phosphuretted Hydrogen

4056.    To Obtain Phosphuretted Hydrogen. The pure gas may be evolved by gently heating hydrated phosphorus acid in a small retort, and collecting it by a pneumatic trough. (See No 4031.)

The spontaneously inflammable variety of this gas is made by boiling phosphorus with solution of potash in a small retort, the beak of which is kept under water : as each bubble of gas rises from the water, it inflames, and forms a ring of white smoke, which dilates as it ascends. The spontaneous inflammability of the gas, when mixed with atmospheric air or oxygen, renders caution necessary in its preparation.

4057. Nitrogen or Azote

4057.     Nitrogen or Azote. An elementary gaseous body. Pure nitrogen is a colorless, odorless, tasteless gas, neither combustible nor capable of supporting combustion or respiration. It is neutral to test paper, does not affect lime water, and is only slightly absorbed by pure water. Liebig places its specific gravity at 0.9722, Berzelius at 0.976.

4058. Tests for Nitrogen

4058.     Tests for Nitrogen. It is recognized by its purely negative qualities, and by its forming nitric acid when mixed with oxygen, and exposed to the electric spark; or "when a jet of hydrogen is burnt in the mixed gases. (Cooley.)

4059. To Obtain Nitrogen

4059.    To Obtain Nitrogen. Atmospheric air may be made to yield an unlimited supply of nitrogen, by exposing it to the action of substances which combine with its oxygen. By burning a small piece of phosphorus, placed on a capsule floating on the water in a pneumatic trough, under a" large bell-glass, and allowing it to stand over the water a few hours, nearly pure nitrogen is obtained, which may be further purified by agitating it with solution of pure potassa. It may be dried by passing it through concentrated oil of vitriol.

Nitrogen may bo evolved by passing chlorine gas into a solution of pure ammonia, and drying, as before, through sulphuric acid.

Another plan, well recommended, is to heat bichromate of ammonia in a retort. The evolved nitrogen is deprived of all aqueous vapor by sulphuric acid as above, or by letting it stand over fused chloride of calcium.