IIRC, Cheapskate mentioned adding MgSO4 to bind water...
i'll try to dig up some data on cryst. temps of some crystallohydrates..... lemmesee....
CaSO4*2H20 : -1,5H2O/128 C; -0,5H2O/163 Ñ
(permanently loses its ability to bind water upon total dehydration)
CaCl2*6H2O : -4H2O/45 C; -2H2O/>250 Ñ
MgBr2*6H2O: mp 172 C (obviously, w/out losing water)
MgSO4*7H2O: -6H2O/150 C; -H2O/200 C
CuSO4*5H2O: -2H2O/100 C; -2H2O/150 C; -H2O/250 Ñ
ZnSO4*7H2O: -7H2O/280 Ñ
ZnCl2 also completely loses water at circa 320 C.
Would that suffice for your needs, amigo?
Seems like MgSO4 or CuSO4 would bee your best bet.
Yours,
Antoncho