化學中的．所代表的意思???

Crystallisation 結晶作用
That means every CuSO4 has 5 H2O, the．only use to link the formula

It means the compound is hydrated by 5 water molecules. In other words, the water molecules are not part of the compound but are present in the solid that you find in the jar.

The solid isn't the pure compound and the water is making the compound heavier than it actually is, so when the water is removed by heat the weight will drop.

"和"的意思，後面是五個結晶水分子