Magnesium sulfate heptahydrate
EUROPEAN PHARMACOPOEIA 9.0
01/2017:0044
MAGNESIUM SULFATE HEPTAHYDRATE
Magnesii sulfas heptahydricus
MgS04,7H20 Mr 246.5
[10034-99-8]
DEFINITION
Content: 99.0 per cent to 100.5 per cent (dried substance). CHARACTERS
Appearance: white or almost white, crystalline powder or brilliant, colourless crystals.
Solubility: freely soluble in water, very soluble in boiling water, practically insoluble in ethanol (96 per cent).
IDENTIFICATION
A. It gives the reactions of sulfates (2.3.2).
B. It gives the reaction of magnesium (2.3.1).
TESTS
Solution S. Dissolve 5.0 g in water R and dilute to 50 mL with the same solvent.
Appearance of solution. Solution S is clear (2.2.1) and colourless (2.2.2, Method II).
Acidity or alkalinity. To 10 mL of solution S add 0.05 mL of phenol red solution R. Not more than 0.2 mL of 0.01 M hydrochloric acid or 0.01 M sodium hydroxide is required to change the colour of the indicator.
Chlorides (2.4.4): maximum 300 ppm.
Dilute 1.7 mL of solution S to 15 mL with water R.
Arsenic (2.4.2, Method A): maximum 2 ppm, determined on 0.5 g.
Iron (2.4.9): maximum 20 ppm.
Dilute 5 mL of solution S to 10 mL with water R.
Loss on drying (2.2.32): 48.0 per cent to 52.0 per cent, determined on 0.500 g by drying in an oven at 110-120 °C for 1 h and then at 400 °C to constant mass.
ASSAY
Dissolve 0.450 g in 100 mL of water R and carry out the
complexometric titration of magnesium (2.5.11).
1 mL of 0.1 M sodium edetate is equivalent to 12.04 mg
ofMgS04.
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MAGNESIUM TRISILICATE
Magnesii trisilicas
DEFINITION
It has a variable composition corresponding approximately
to Mg2Si308,xH20
Content:
- magnesium oxide (MgO; Mr 40.30): minimum 29.0 per cent (ignited substance),
- silicon dioxide (Si02; Mr 60.1): minimum 65.0 per cent (ignited substance).
CHARACTERS
Appearance: white or almost white powder.
Solubility: practically insoluble in water and in ethanol (96 per
cent).
IDENTIFICATION
A. 0.25 g gives the reaction of silicates (2.3.1).
B. 1 mL of solution S (see Tests) neutralised with dilute sodium hydroxide solution R gives the reaction of magnesium (2.3.1).
TESTS
Solution S. To 2.0 g add a mixture of 4 mL of nitric acid R and 4 mL of distilled water R. Heat to boiling with frequent shaking. Add 12 mL of distilled water R and allow to cool. Filter or centrifuge to obtain a clear solution and dilute to 20 mL with distilled water R.
Alkalinity. To 10.0 g in a 200 mL conical flask, add 100.0 g of water R and heat on a water-bath for 30 min. Allow to cool and make up to the initial mass with water R. Allow to stand and filter or centrifuge until a clear liquid is obtained. To 10 mL of this liquid add 0.1 mL of phenolphthalein solution R. Not more than 1.0 mL of 0.1 M hydrochloric acid is required to change the colour of the indicator.
Water-soluble salts: maximum 1.5 per cent. In a platinum dish, evaporate to dryness on a water-bath 20.0 mL of the liquid obtained in the test for alkalinity. The residue, ignited to constant mass at 900 ± 50 °C, weighs a maximum of 30 mg.
Chlorides (2.4.4): maximum 500 ppm.
Dilute 0.5 mL of solution S to 15 mL with water R. Prepare the standard using a mixture of 5 mL of chloride standard solution (5 ppm CI) R and 10 mL of water R.
Sulfates (2.4.13): maximum 0.5 per cent.
Dilute 0.3 mL of solution S to 15 mL with distilled water R.
Arsenic (2.4.2, method A): maximum 4 ppm, determined on 2.5 mL of solution S.
Loss on ignition: 17 per cent to 34 per cent, determined on 0.5 g by ignition to constant mass at 900 ± 50 °C in a platinum crucible.
Acid-absorbing capacity. Suspend 0.25 g in 0.1 M hydrochloric acid, dilute to 100.0 mL with the same acid and allow to stand for 2 h in a water-bath at 37 ± 0.5 °C, with frequent shaking. Allow to cool. To 20.0 mL of the supernatant solution add 0.1 mL of bromophenol blue solution R and titrate with 0.1 M sodium hydroxide until a blue colour is obtained. The acid-absorbing capacity is not less than 100.0 mL of 0.1 M hydrochloric acid per gram.
ASSAY
Magnesium oxide. To 1.000 g in a 200 mL conical flask, add 35 mL of hydrochloric acid R and 60 mL of water R and heat in a water-bath for 15 min. Allow to cool, filter, wash the conical flask and the residue with water R and dilute the combined filtrate and washings to 250.0 mL with water R. Neutralise 50.0 mL of the solution with strong sodium hydroxide solution R (about 8 mL). Carry out the complexometric titration of magnesium (2.5.11).
1 mL of 0.1 M sodium edetate is equivalent to 4.030 mg of MgO.
Silicon dioxide. To 0.700 g add 10 mL of dilute sulfuric acid R and 10 mL of water R. Heat for 90 min on a water-bath with frequent shaking, replacing the evaporated water. Allow to cool and decant onto an ashless filter paper (diameter 7 cm). Wash the precipitate by decantation with 3 quantities, each of 5 mL, of hot water R, transfer it to the filter and wash it with hot water R until 1 mL of the filtrate remains clear after the addition of 0.05 mL of dilute hydrochloric acid R and 2 mL
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See the information section on general monographs (cover pages)