This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
Iodide of sodium should be kept in well-stopped bottles. Minute, colorless or white, monoclinic crystals, or a crystalline powder, deliquescent on exposure to air, odorless, having a saline and slightly bitter taste, and a neutral or faintly alkaline reaction. Soluble in 0.6 part of water, and in 1.8 parts of alcohol at 15° C. (59° F.); in 0.3 part of boiling water, and in 1.4 parts of boiling alcohol. This salt is dissolved for immediate use, one part in nine parts of distilled water. If a solution be kept in stock, which is not advisable, it easily absorbs oxygen and carbonic acid from the air and separates iodide.