D.M. Procida wrote:

If I pour off the liquid, and leave the solid mass in a warm dry place,
say on top of a radiator, will it be any good at absorbing moisture from
the air once again?

No, the solid mass is a mixture of calcium sulphate and calcium
carbonate -- basically trash impurities, because the "calcium chloride"
sold for these things is far from pure.

If you were to heat the calcium chloride solution and evaporate it, you
could recover the calcium chloride and re-use that. OTOH you'd probably
have to pay the energy costs of doing so. If you had a big damp problem
and a source of waste heat, then it _might_ start to make sense.