The pentahydrate (n = 5), a bright blue crystal, is the most commonly encountered hydrate of copper(II) sulfate,[10] while its anhydrous form is white.

[14] It exothermically dissolves in water to give the aquo complex [Cu(H2O)6]2+, which has octahedral molecular geometry.

Copper sulfate is often used to demonstrate an exothermic reaction, in which steel wool or magnesium ribbon is placed in an aqueous solution of CuSO4.

When water is then added to the anhydrous compound, it turns back into the pentahydrate form, regaining its blue color.

[22][23] Bordeaux mixture, a suspension of copper(II) sulfate (CuSO4) and calcium hydroxide (Ca(OH)2), is used to control fungus on grapes, melons, and other berries.

[27] Clinically relevant, however, modern laboratories utilize automated blood analyzers for accurate quantitative hemoglobin determinations, as opposed to older qualitative means.

[29] The hydrated salt can be intimately mingled with potassium permanganate to give an oxidant for the conversion of primary alcohols.

[30] Reaction with ammonium hydroxide yields tetraamminecopper(II) sulfate or Schweizer's reagent which was used to dissolve cellulose in the industrial production of Rayon.

[31] In 2008, the artist Roger Hiorns filled an abandoned waterproofed council flat in London with 75,000 liters of copper(II) sulfate water solution.

The solution was left to crystallize for several weeks before the flat was drained, leaving crystal-covered walls, floors and ceilings.

[citation needed] An aqueous solution of copper(II) sulfate is often used as the resistive element in liquid resistors.

[citation needed] In electronic and microelectronic industry a bath of CuSO4·5H2O and sulfuric acid (H2SO4) is often used for electrodeposition of copper.

Other rare copper sulfate minerals include bonattite (trihydrate),[41] boothite (heptahydrate),[42] and the monohydrate compound poitevinite.

[50] It is still listed as an antidote in the World Health Organization's Anatomical Therapeutic Chemical Classification System.