Hydriodic Acid

(Chem.) A gas composed of hydrogen and iodine. It is obtained by placing a little iodine in a gla tube, upon this some roughly powdered gla moistened with water, and then a few pieces of phosphorus, and finally more gla , and so on till the tube is two-thirds full. Gentle heat is then applied, and the gas collected by the displacement of air. The gla serves to prevent the too violent action of the iodine upon the phosphorus. H. A. resembles hydrochloric acid, q.v., is colorle , highly acid, fumes in the air, and is very soluble in water. Its solution in water is a sour, dense liquid, which is gradually decomposed by the oxygen of the air; the iodine set free being di olved communicates to the liquid a brown color. It is also decomposed by chlorine.