(...) With this procedure the ordinary 95° alcool can be dehydrated easily to 99/100°.
Experimental:
Anhydrous copper sulfate, obtained by the calcination of ordinary hydrated copper sulfate (or by another way), is added to the alcohol you want to dehydrate in an apparatus with a stirbar and is left in contact for 10-12 h, with stiring from times to times. If some heat is applied, like 45°C, the process is faster.
It is good to put twice the theoretical amount of anhydrous CuSO4, for the reaction to not take too much time. For instance, with 100 kg of 95° alcohol, it take 20 to 25 kg of anh. CuSO4. At the end of the reaction the clear liquid is decanted and can be filtered to remove the remaining CuSO4 suspended, or can be placed in a tank to sediment. If distillation of the alcohol is performed instead of decantation, some water is left in the alcohol. Yields are 85 to 90% of 99° alcohol (measured on the initial quantity of pure alcool). The remaining alcohol impregnated on the hydrated CuSO4 is recovered by distillation. This fraction is not anhydrous and must be recycled in another experiment.
If really absolute alcool is necessary, it is good (to save time and to not put too much sulfate at once) to put the 99° alcohol on fresh anhydrous copper sulfate which then react faster. The hydrated CuSO4 is calcinated and recycled.
Some changes can be made on the procedure without much problem.