Description

Chromium Sulphate

Basic chromium sulfate is an inorganic compound with the chemical formula Cr(OH)(SO4). It is a green, odorless solid at room temperature. It is typically sold in powder form. Basic chromium sulfate has high tanning power and hence largely used in the tanning of leather. It is easily soluble in cold water and very soluble in hot water. Chromium, particularly in the hexavalent oxidation state, is toxic, hence basic chromium sulfate, which is comparatively less toxic, is preferred in the leather industry.

Tanning Industry
Abundant quantity of chromium (III) sulphateis used as a tanning agent in the leather industry. In the tanning process the tanning agent alters the structure of animal protein, which is present in animal hides and skin. Chromium sulphate penetrates itself in collagen fibres at increased pH and undergoes olation and oxolation processes to give polychromium compounds. Chromium has an excellent ability to form stable bridge bonds. Tanning increase spacing between the protein chains and the space is filled with polychrome species.

Metal plating
Chromium sulphate (specially modified) can be used for chromium metal plating in the automobile industry and to manufacture decorative plating utensils. It provides corrosion resistance and surface hardness. Trivalent chrome plating is an alternative to hexavalent chrome plating. Chromium sulphate is the main ingredient of trivalent chrome plating and applicable for decorative coating.

Advantages of chromium sulphate plating over hexavalent chrome plating
• From a health standpoint hexavalent chromium is more toxic than the trivalent chromium sulphate
• Chromium sulphate coating gives higher cathode efficiency.
• Higher cathode efficiency leads to better throwing powder which gives very even and smooth plating in the corners and the surface.
• In trivalent plating anodes do not decompose. Shielded graphite or composites are used with the oxidation preventing additives such as sulphuric acid, which prevents the oxidation of chromium.

Dyeing and printing
Chromium sulphateis used to produce dyestuffs and colouring pigments. It can be used as a mordant dye in textile dyeing which can be directly formed on the fiber. Mordant are compounds with coordination complexes. It is applicable to make insoluble compounds or chrome salts which are used to form pigments used in paint and ink. Usually dichromates such as potassium and sodium dichromatesare used for dyestuff, but chromium (III) compounds are much less toxic than chromium (IV) and (VI) compounds.

Other applications
It is used in the preparation of ceramic glazes. It is used for production of Green ink, making protein and other organic substances insoluble. In dyeing, it is applicable to produce reactive black dye. It is used in chromium industry to obtain chrome alloys when it is specially modified for metal industry application. It is used in automotive parts finishing. It is also used as a coating auxiliary agent.