Caesium chloride, CsCl

The Caesium chloride, CsCl, is prepared similarly to that of rubidium. It forms cubes, melting at 626° C., 631° C., 645° C., 646° C. or 647° C., and boiling at 1303° C. The vapour-pressure in atmospheres is given by the expression

log p = -37400/4.57T + 5.190.

The substance has a density of 3.972 or 3.987 at 20° C., and 3.982 at 23.1° C. Its latent heat of fusion per gram is 0.024 Cal. The hygroscopic salt is very readily soluble in water, yielding a neutral solution. The solubility is given in the appended table:

Solubility of Caesium Chloride.

Temperature, °C.	0	10	20	30	40	50	60	70	80	90	100
Grams of CsCl per 100 g. of water	161.4	174.7	186.5	197.3	208.0	218.5	229.0	239.5	250.0	260.1	270.5

The heat of solution is -4.68 Cal., and the heat of formation 109.86 Cal. A saturated solution boils at 119.9° C. under 760 mm. pressure. Caesium chloride resembles the rubidium salt in forming a number of complex polyhalides. It is a useful agent in photomicrography, since it forms well-defined double salts with many metals among them - silver, gold, platinum, mercury, lead, copper, and many others. It has a decided toxic effect.