NaCl + HO SO3 = NaO SO3 + HCl.
Properties.—Abundantly soluble in water, forming the liquid Hydrochloric or Muriatic Acid of commerce. The most concentrated solution of Hydrochloric Acid has a sp. gr. 1·2, and contains about 40 per cent, of gas; that commonly sold is somewhat weaker, sp. gr. 1·14 = 28 per cent, real acid.
Pure Hydrochloric Acid is colourless, and fumes in the air. The yellow colour of the commercial acid depends upon the presence of traces of Perchloride of Iron, or of organic matter; commercial Muriatic Acid also often contains a portion of free Chlorine and of Sulphuric Acid.
HYDRIODIC ACID.
Symbol, HI. Atomic weight, 127.
This is a gaseous compound of Hydrogen and Iodine, corresponding in composition to the Hydrochloric Acid. It cannot however, from its instability, be obtained in the same manner, since, on distilling an Iodide with Sulphuric Acid, the Hydriodic Acid first formed is subsequently decomposed into Iodine and Hydrogen. An aqueous solution of Hydriodic Acid is easily prepared by adding Iodine to water containing Sulphuretted Hydrogen gas; a decomposition takes place, and Sulphur is set free: thus, HS + I = HI + s.
Properties.—Hydriodic Acid is very soluble in water, yielding a strongly acid liquid. The solution, colourless at first, soon becomes brown from decomposition, and liberation of free Iodine. It may be restored to its original condition by adding solution of Sulphuretted Hydrogen.
Symbol, HS. Atomic weight, 17.