4066. Sulphurous Acid

4066.      Sulphurous Acid. This is a gaseous combination of 1 equivalent of sulphur and 2 of oxygen, having a specific gravity of 1.45, and very soluble in water, which will absorb 30 times its volume of the gas. Its properties, preparation, and application to the arts, will be found in Nos. 3864, etc..

4067. Ammonia

4067.     Ammonia. A highly pungent gas formed by the union of 1 equivalent of nitrogen with three of hydrogen. Its specific gravity is .589. (See Nos. 3981 (Ammonia), etc..) Double salts of ammonia are sometimes called am-moniurets. Thus, sulphate or nitrate of copper precipitated in solution by ammonia, and the precipitate redissolved by an excess of ammonia, may be called ammoniurets of copper, but more correctly ammonio-sulphate, or ammonia-nitrate of copper.

4068. Hydrochloric Acid

4068.    Hydrochloric Acid. A gaseous acid formed of equal equivalents of hydrogen and chlorine. (See Nos. 3882 (Muriatic or Hydrochloric Acid), etc..)

4069. Chlorine

4069.    Chlorine. An elementary gas, of a yellowish green color, a pungent, suffocating odor, and an astringent taste. Its specific gravity is 2.47. Under a pressure of 4 atmospheres it condenses into a yellow limpid liquid. Its most remarkable properties are its power of destroying almost all animal and vegetable color, and the putrid odor of decomposing organic matter. It has a very strong attraction for metals. With bases chlorine forms chlorides or chlorurets. (See No. 3853.)

4070. To Obtain Chlorine

4070.    To Obtain Chlorine. This gas is obtained, for laboratory use, etc., by mixing together in a glass flask or retort, strong muriatic acid with half of its weight of finely-powdered peroxide of manganese. Or: Pour common muriatic acid, diluted with an equal weight of water, upon half its weight of chloride of lime. Chlorine gas is immediately evolved even in tho cold, but much more rapidly on tho application of a gentle heat. This gas must bo collected in clean dry bottles by displacement. The tube conducting tho gas must reach to tho bottom of tho bottle, when tho chlorine, being heavier than tho air, will displace tho latter, without mixing with it. Tho bottle is known to bo full by tho gas overflowing the mouth, which is easily perceived by its green color. The bottle must now bo closed up with an accurately fitting stopper, previously greased, and an empty one put in its place, which is subsequently treated in like manner. To free tho gas entirely from muriatic acid, it may bo passed through water; and to render it dry, it may bo passed over dry chloride of calcium. Chlorine gas may also bo collected over a saturated solution of common salt in tho pneumatic trough, if the presence of moisture be no objection. (See No. 4031 (Pneumatic Trough).)

4071. Tests for Chlorine

4071.    Tests for Chlorine. This gas is readily distinguished from other gases by its color, odor, and bleaching properties. Its aqueous solution dissolves gold leaf, and instantly blackens a piece of silver plunged into it. It rapidly destroys the color of iodide of starch, solution of indigo, litmus, and turmeric. A simple method of detecting free chlorine is to hold a rod, dipped in water of ammonia, over it, when white fumes of sal-ammoniac will bo formed; this, coupled with the property of bleaching colors, may, in most cases, bo taken as evidence of tho presence of this substance.