How to convert Zinc Sulfate Monohydrate (ZnSO4.H2O) to Zinc Sulphate Heptahydrate (ZnSO4.7H2O). Please understand it is not as "simple" as mixing Zinc Sulfate Monohydrste it with excess water and boiling it up to 1500 gravity and then waiting for it to crystalize as zinc Sulfate Heptahydrate.

It seems to me that if you supersaturate your compound in water and then crystallize it back out, you will have the highest stable hydrate. If you were looking to make a 6 molecule hydrate you would then heat it to 30 C to dehydrate it slightly. At 70 C it would then go back to the Monohydrate status.

You can test it simply just by crystallizing it in water drying it at say no more than 25 C and weigh it out in order to test how much water has remained in the crystal. You can dry it on the scale and check it out hourly to see when evaporation ceases.

Good Luck