How can't Mgcl absorb water in the air?

[oksys]

We would like to use Mgcl without absorbing water in the air.
But We can't.

Anybody help us this problem?

Donald.

 

[25362]

Chemistry books tell that a fairly general reagent to remove the attached water molecules is 2,2-dimethoxypropane.

MgCl₂.mH₂O+mCH₃C(OCH₃)₂CH₃=>MgCl₂+m(CH₃)₂CO + 2mCH₃OH

I've read elsewhere that the formed acetone and/or methanol may coordinate with the metal; gentle heating usually gives the solvate-free halide.

Another reagent for the same purpose is SOCl₂ which, when under reflux, gives the anhydrous halide, HCl and SO₂.

Heating hydrated halides under vacuum is sometimes used to dehydrate them. But this operation often leads to oxo halides or impure products.