Rubidium chloride, RbCl

The Rubidium chloride, RbCl, is produced by the interaction of hydrochloric acid and rubidium carbonate, and also by heating rubidium chloroplatinate. It forms lustrous cubes, stated to melt at 710° C., 712° to 713° C., 713° C., 714° C., 717° C., and 726° C., and to boil at 1383° C. The vapour-pressure in atmospheres is given by the expression

log p = -37800/4.57T+4.998.

Its density is recorded as 2.209, 2.706 at 22.9° C. (Buchanan), and 2.762 at 20° C. (Haigh). Its specific heat is 0.112 between 16° and 45° C., and the latent heat of fusion per gram is 0.038 Cal. The heat of formation in aqueous solution from the elements is 105.94 Cal. The salt does not form hydrates, but is very soluble in water.

Solubility of Rubidium Chloride

Temperature, °C.	0	10	20	30	40	50	60	70	80	90	100
Grams of RbCl per 100 grams of water	77.0	84.4	91.1	97.6	103.5	109.3	115.5	121.4	127.2	133.1	138.9

The boiling-point of the saturated solution in contact with excess of the salt is 113.71° C. at 760 mm. pressure, and the heat of solution is -4.5 Cal. At 25° C. 100 grams of ethyl alcohol dissolve 0.078 gram. The salt unites with free halogens, yielding various polyhalides, and also forms double chlorides with other metallic chlorides. It exhibits radioactivity.