Description
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.
Uses
Strontium iodide is a yellowish granular powder made by
treating strontium carbonate with hydriodic acid. It is soluble
in water, alcohol, and ether. Strontium iodide was occasionally
used to increase contrast in collodion emulsions.
