Calcium hypochlorite

Calcium hypochlorite or Calcium oxychloride
Other names Hypochlorous acid, calcium salt Bleaching powder, Calcium oxychloride
Identifiers
CAS number	7778-54-3 Y
ChemSpider	22912 Y
EC number	231-908-7
UN number	1748
RTECS number	NH3485000
Jmol-3D images	Image 1
SMILES [Ca+2].[O-]Cl.[O-]Cl
InChI InChI=1S/Ca.2ClO/c;2*1-2/q+2;2*-1 Y Key: ZKQDCIXGCQPQNV-UHFFFAOYSA-N Y InChI=1/Ca.2ClO/c;2*1-2/q+2;2*-1 Key: ZKQDCIXGCQPQNV-UHFFFAOYAV
Properties
Molecular formula	Ca(ClO)2
Molar mass	142.98 g/mol
Appearance	white/gray powder
Density	2.35 g/cm3 (20 °C)
Melting point	100 °C
Boiling point	175 °C, decomposes
Solubility in water	21 g/100 mL, reacts
Solubility	reacts in alcohol
Hazards
MSDS	ICSC 0638
EU Index	017-012-00-7
EU classification	Oxidant (O) Corrosive (C) Harmful (Xn) Dangerous for the environment (N)
R-phrases	R8, R22, R31, R34, R50
S-phrases	(S1/2), S26, S36/37/39, S45, S61
NFPA 704	0 3 1 OX
Flash point	Non-flammable
LD50	850 mg/kg (oral, rat)
Related compounds
Other anions	Calcium chloride
Other cations	Sodium hypochlorite
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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).

Preparation

It is manufactured by the calcium process:

$~\mathrm{2Cl_2 + 2Ca(OH)_2\longrightarrow \ Ca(OCl)_2 + CaCl_2 + 2H_2O}$.

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

Properties

Calcium hypochlorite is a yellow white solid which has a strong smell of chlorine. It is not highly soluble in water, and is more preferably used in soft to medium-hard water. It has two forms: 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 dichlorine monoxide:

$~\mathrm{Ca(ClO)_2 + CO_2\longrightarrow \ CaCO_3 + Cl_2O \uparrow}$.

A calcium hypochlorite solution is basic. This is due to the hydrolysis performed by the hypochlorite ion, as hypochlorous acid is weak, but calcium hydroxide is a strong base. As a result, the hypochlorite ion is a strong conjugate base, and the calcium ion is a weak conjugate acid:

ClO⁻ + H₂O → HClO + OH⁻

Similarly, calcium hypochlorite reacts with hydrochloric acid to form calcium chloride, water and gaseous chlorine:

Ca(OCl)₂ + 4 HCl → CaCl₂ + 2 H₂O + 2 Cl₂

Uses

Calcium hypochlorite is used for the disinfection of drinking water or swimming pool water. It is used as a sanitizer in outdoor swimming pools in combination with a cyanuric acid stabilizer, which reduces the loss of chlorine due to ultraviolet radiation. The calcium content hardens the water and tends to clog up some filters; hence, some products containing calcium hypochlorite also contain anti-scaling agents.

Calcium hypochlorite is also an ingredient in bleaching powder, used for bleaching cotton and linen. It is also used in bathroom cleaners, household disinfectant sprays, moss and algae removers, and weedkillers.

In addition, calcium hypochlorite may be used to manufacture chloroform.

Bleaching powder is used also in sugar industry for bleaching sugar cane juice before its crystallization.

Safety

Calcium hypochlorite is best kept in a cool dry place away from any organic material. It is known to undergo self heating and rapid decomposition accompanied by the release of toxic chlorine gas.^{[citation needed]}

External links

• Chemical Land