HYDRIODIC ACID

A gaseous compound of hydrogen and iodine, obtained by the mutual decomposition of iodide of phosphorus and water. It is composed of 126 iodine -^ 1 hydrogen; and its equivalent, therefore, is 127. The specific gravity of this gas is 4-4. One hundred cubic inches weigh 136 grains. It is rapidly absorbed by water, furnishing a sour, colourle , and dense liquid, which soon becomes brown by exposure to air, in consequence of the evolution of a little free iodine. It is instantly decomposed by chlorine, which abstracts the hydrogen to form hydrochloric (muriatic) acid, and sets the iodine free. [s. 585]