and what other substances can also do the same job as anhydrous copper sulphate and what is the colour change?
Anhydrous copper sulphate can be used as a qualitative indicator for water. The grey/ white anhydride turns blue in the presence of water. Another product that has these characteristics is cobalt chloride. In the presence of moisture the salt has a red colour, and the anhydrate is blue.Because of its distinct color change and the ease of hydration/dehydration , cobalt chloride is used as an indicator for water. It is usually combined with silica gel, which is a strong desiccant. When the silica gel has absorbed the maximum water, the indicator turns from blue to red. Drying the silica gel in an oven drives off the water and the substance can be used again.
