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Strontium iodide (SrI2) is an ionic, water-soluble, deliquescent compound that has been used in medicine as a substitute for potassium iodide. Strontium iodide crystals are colorless, transparent, hexagonal in structure, and have a bitter, saline taste. Soluble in 0.6 part of water at 15°C, they are also soluble in alcohol.
Strontium iodide can be prepared by reacting strontium carbonate with hydroiodic acid:
SrCO3＋2HI→SrI2＋H2O＋CO2
Strontium iodide turns yellow when exposed to air due to the formation of iodine at the surface of the crystals. At high temperatures (when in the presence of air), strontium iodide completely decomposes to form strontium oxide and free iodine.
Several hydrates are known including SrI2·6H2O. This salt is a white crystalline substance composed of small plates. It decomposes in moist air due to its deliquescence. Its specific gravity varies from 4.415 g/cm3 to 4.549 g/cm3, depending upon how the crystals are formed. It loses water at 78°C and the anhydrate forms above 200°C. The melting point of SrI2 is 507°C and its boiling point is 645°C where it decomposes to the oxide and iodine.

White to yellowish white crystalline powder

Toxic by ingestion and inhalation.

Preparation of anhydrous strontium iodide from strontium carbonate and hydriodic acid:
1. SrCO₃ reacts with HI to pH ~5.5. The pH is adjusted to 7.5 and the solution is filtered.
2. The solution is concentrated and cooled to crystallize. Recrystall