Rubidium iodide, RbI

The Rubidium iodide, RbI, is formed by the action of hydriodic acid on rubidium carbonate, and crystallizes in colourless cubes, its melting-point being given as 641.5° C. and 642° C. The boiling-point is 1305° C.,3 and the vapour-pressure in atmospheres is given by the expression

log p = -37000/4.57T+5.148.

Its density is stated to be 3.023, 3.447, 3.428 at 24.3° C., and 3.438 at 25° C. At 17.4° C. its solubility is 152 grams in 100 grams of water, the heat of solution being -6.5 Cal. Poly iodides such as RbI₃, RbI₇, and RbI₉ have been isolated.