Calcium Sulphate

Calcium Sulphate Dihydrate BP

CaSO4,2H2O ... 172.2

Action and use
Excipient.

DEFINITION
Content
98.0 per cent to 102.0 per cent of CaSO4,2H2O i.e. Calcium Sulphate Dihydrate or Calcium Sulfate Dihydrate.

CHARACTERS
Appearance
White or almost white fine powder.
Solubility
Very slightly soluble in water, practically insoluble in ethanol (96 per cent).

IDENTIFICATION
Loss on ignition.
Solution S gives reaction of sulphates.
Solution S gives reaction of calcium.

TESTS
Solution S
Dissolve 1.0 g in 50 ml of a 10 per cent V/V solution of hydrochloric acid R by heating at 50°C for 5 min. Allow to cool.
Acidity or alkalinity
Shake 1.5 g with 15 ml of carbon dioxide-free water for 5 min. Allow to stand for 5 min and filter. To 10 ml of the filtrate add 0.1 ml of phenolphthalein solution and 0.25 ml of 0.01 M sodium hydroxide. The solution is red. Add 0.30 ml of 0.01 M hydrochloric acid. The solution is colourless. Add 0.2 ml of methyl red solution. The solution is reddish-orange.
Chlorides
Maximum 300 ppm.
Shake 0.5 g with 15 ml of water R for 5 min. Allow to stand for 15 min and filter. Dilute 5 ml of the filtrate to 15 ml with water.
Arsenic
Maximum 10 ppm, determined on 5 ml of solution S.
Iron
Maximum 100 ppm.
To 0.25 g add a mixture of 5 ml of hydrochloric acid R and 20 ml of water R. Heat to boiling, cool and filter.
Heavy metals
Maximum 20 ppm.
To 2.5 g add a mixture of 2 ml of hydrochloric acid R and 15 ml of water R. Heat to boiling. Cool and then add 0.5 ml of phenolphthalein solution R. Cautiously add concentrated ammonia until the colour changes to pink. Add 0.5 ml of glacial acetic acid R and dilute to 25 ml with water R. Filter. 12 ml of the filtrate complies with test A. Prepare the reference solution using lead standard solution (2 ppm Pb.
Loss on ignition
18.0 per cent to 22.0 per cent, determined on 1.000 g by ignition to constant mass at 800 ± 50C.

ASSAY
Dissolve 0.150 g in 120 ml of water. Carry out the complex o metric titration of calcium.
1 ml of 0.1 M sodium edetate is equivalent to 17.22 mg of CaSO4,2H2O.

Calcium Sulfate USP

Calcium Sulfate USP
CaSO4 136.14
Sulfuric acid, calcium salt (1:1)
Calcium sulfate (1:1) 136.14
Dihydrate 172.17

Calcium Sulfate is anhydrous or contains two molecules of water of hydration. It contains not less than 98.0 percent and not more than 101.0 percent of CaSO4 i.e. Calcium Sulfate or Calcium Sulphate, calculated on the dried basis.