Drugs & Medication

Calcium hypochlorite
Systematic name	Calcium hypochlorite
Other names	HTH
Molecular formula	Ca(ClO)2
Molar mass	143.1 g/mol

Calcium hypochlorite is a chemical compound with formula Ca(ClO)₂. It is widely used for water treatment and as a bleaching agent (bleaching powder). This chemical is considered to be relatively stable and has greater available chlorine than sodium hypochlorite (liquid bleach).

Contents 1 Preparation 2 Properties 3 Uses

Preparation

It is manufactured using the calcium process and sodium process. Or it can be prepared by the action of slaked lime on chlorine:

Ca(OH)₂ + Cl₂ → Ca(OCl)₂ + H₂

Bleaching powder is actually a mixture of calcium hypochlorite Ca(OCl)₂ and the basic chloride CaCl₂, Ca(OH)₂, H₂O with some slaked lime, Ca(OH)₂.

Properties

It is a yellow white solid which has a strong smell of chlorine. Calcium hypochlorite is not highly soluble in water. For that reason it should preferably be used in soft to middle hard water. There are two types of calcium hypochlorite - a dry form and a hydrated form. The hydrated form is safer to handle.

Calcium hypochlorite reacts with carbon dioxide to form calcium carbonate and release chlorine:

Ca(OCl)₂ + CO₂ → CaCO₃ + Cl₂

Calcium hypochlorite reacts with hydrochloric acid to form calcium chloride:

Ca(OCl)₂ + 2 HCl → CaCl₂ + H₂O + Cl₂

Uses

Calcium hypochlorite is used for the disinfection of drinking water or swimming pool water. For use in outdoor swimming pools, calcium hypochlorite can be used as a sanitiser in combination with a cyanuric acid stabiliser. The stabiliser will reduce the loss of chlorine because of UV radiation.

Calcium hypochlorite (known as 'bleaching powder') is also used for bleaching cotton and linen and used in the manufacture of chloroform.