Zinc Iodate, Zn(IO₃)₂

Zinc Iodate, Zn(IO₃)₂.2H₂O, is obtained as a white crystalline powder by interaction between sodium iodate and a zinc salt. It is sparingly soluble in water, but a very soluble modification may exist.

It can also be prepared by dissolving zinc or zinc carbonate in aqueous hydriodic acid, and needle-shaped crystals of the anhydrous salt are said to be obtained by crystallising in the presence of much nitric acid, or evaporating at 60° C. a solution of the iodate in phosphoric acid.

The dihydrate loses its moisture at 200° C., and decomposes at a red heat into iodine, oxygen, and zinc oxide.

Efflorescent rhombic prisms, decomposed by water, of 3Zn(IO₃)₂. 8NH₄, are obtained by dissolving zinc iodate in concentrated ammonia solution, and either adding alcohol or allowing the solution to evaporate spontaneously. Another compound with ammonia, insoluble in water and stable in air, has been obtained by slow evaporation of an ammoniacal solution of zinc iodate. It decomposes explosively at 150° C. Dry powdered zinc iodate absorbs ammonia gas to form Zn(IO₃)₂.4NH₄.