DICHROMATE

This is an orange, crystalline substance with a specific gravity of 2.68. Solubility in water is 11.7% at 20 °C. Both potassium and sodium dichromate are used in mineral processing.Dichromate solutions have an acid reaction because Cr₂O₇^2- ion reacts with water as follows: H2O + Cr₂O₇^2- ? HCr₂O^4- + H⁺ + CrO^4-
Salts of chromic acid in acid medium are oxidants (Cr^4- changes to Cr^3- ). In principle, dichromates are used in selective separation of copper–lead bulk concentrates, usually in acid pH. A mixture of sodium dichromate and sodium silicate has shown to be an excellent lead depressant during copper flotation from a bulk copper–lead concentrate containing secondary copper minerals.