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 sulphates.
B. It gives the reaction of magnesium.
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 and colourless.
Acidity or alkalinity:
To 10 ml of solution S add 0.05 ml of phenol red solution. 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:
Maximum 300 ppm.
Arsenic:
Maximum 2 ppm, determined on 0.5 g.
Iron:
Maximum 20 ppm.
Heavy metals:
Maximum 10 ppm.
Loss on drying:
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.
Magnesium Sulfate, rendered anhydrous by ignition, contains not less than 99.0 percent and not more than 100.5 percent of MgSO4.
Identification: A solution (1 in 20) responds to the tests for Magnesium and
for Sulfate.
pH: between 5.0 and 9.2, in a solution (1 in 20).
Loss on drying: Dry it at 105 for 2 hours: the anhydrous form loses not more
than 2% of its weight.
Loss on ignition: Weigh accurately about 1 g in a crucible, heat at 105 for 2
hours, then ignite in a muffle furnace at 450 ± 25 to constant weight: the
monohydrate loses between 13.0% and 16.0% of its weight, the dried form loses
between 22.0% and 28.0% of its weight, and the heptahydrate loses between 40.0% and
52.0% of its weight.
Chloride: A 1.0-g portion shows no more chloride than corresponds to 0.20 mL
of 0.020 N hydrochloric acid (0.014%).
Iron:
FOR MAGNESIUM SULFATE INTENDED FOR USE IN PREPARING NON-PARENTERAL DOSAGE
FORMS—
Dissolve 0.50 g in 40 mL of water and proceed as directed in the test for Iron: the
limit is 20 µg per g.
FOR MAGNESIUM SULFATE INTENDED FOR USE IN PREPARING PARENTERAL DOSAGE FORMS: the
limit is 0.5 µg per g.
Heavy metals: Dissolve 2 g in 25 mL of water: the limit is 0.001%.
Selenium: The limit is 0.003%.
DESCRIPTION
Magnesium Sulfate occurs as a colorless crystal or a granular crystalline powder. It
is produced with one or seven molecules of water of hydration or in a dried form
containing the equivalent of about 2.3 waters of hydration. It is readily soluble in
water, slowly soluble in glycerin, and sparingly soluble in alcohol.
Function: Nutrient.
REQUIREMENTS
Identification: A 1:20 aqueous solution gives positive tests for Magnesium
and for Sulfate.
Assay: Not less than 99.5% of MgSO4 after ignition.
Lead: Not more than 4 mg/kg.
Loss on Ignition Monohydrate: Between 13.0% and 16.0%; Heptahydrate: Between
40.0% and 52.0%; Dried: Between 22.0% and 28.0%.
Selenium: Not more than 0.003%.
REQUIREMENTS
Assay: 98.0-102.0% MgSO4-7H2O
pH of a 5% solution: 5.0-8.2 at 25C
MAXIMUM ALLOWABLE
Insoluble matter: 0.005%
Chloride (Cl): 5 ppm
Nitrate (NO3): 0.002%
Ammonium (NH4): 0.002%
Calcium (Ca): 0.02%
Manganese (Mn): 5 ppm
Potassium (K): 0.005%
Sodium (Na): 0.005%
Strontium (Sr): 0.005%
Heavy metals (as Pb): 5 ppm
Iron (Fe): 5 ppm
