Dried Epsom Salts or Magnesium Sulphate Dried
Preparation
Magnesium Sulphate Paste
DEFINITION
Dried Magnesium Sulphate contains not less than 62.0% and not more than 70.0% of MgSO4.
It may be prepared by drying magnesium sulphate at 100° until it has lost approximately 25% of its weight.
CHARACTERISTICS
A white powder.
Freely soluble in water; dissolves more rapidly in hot water.
IDENTIFICATION
Yields the reactions characteristic of magnesium salts and of sulphates.
TESTS
Acidity or alkalinity
To 10 ml of a 7.5% w/v solution in carbon dioxide-free water add 0.05 ml of phenol red solution. Not more than 0.2 ml of either 0.01M hydrochloric acid VS or 0.01M
sodium hydroxide VS is required to change the colour of the solution.
Arsenic
0.33 g dissolved in 25 ml of water complies with the limit test for arsenic, (3 ppm).
Heavy metals
Dissolve 1.3 g in 20 ml of water and add 1 g of ammonium chloride. 12 ml of the resulting solution complies with limit test A for heavy metals, Appendix VII. Use
lead standard solution(1 ppm Pb) to prepare the standard (15 ppm).
Iron
0.33 g dissolved in 10 ml of water complies with the limit test for iron, Appendix VII (30 ppm).
Chloride
0.13 g dissolved in 15 ml of water complies with the limit test for chlorides, Appendix VII (400 ppm).
Insoluble matter
7.5 g dissolves in 20 ml of water, producing a solution which may be slightly turbid at first but which becomes clear in a few minutes.
British Pharmacopoeia 2009
Magnesium Sulphate Heptahydrate
Epsom Salts
MgSO4,7H2O 246.5 10034-99-8
Action and use
Osmotic laxative; used in treatment of electrolyte deficiency.
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.
MgSO4·xH2O
Sulfuric acid magnesium salt (1:1), hydrate.
Magnesium sulfate (1:1) monohydrate 138.36
Magnesium sulfate (1:1) heptahydrate 246.48 [10034-99-8].
Anhydrous 120.37 [7487-88-9].
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) resonds 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%.
Epsom Salt
MgSO4·xH2O Formula wt, monohydrate 138.38
Formula wt, heptahydrate 246.47
INS: 518
CAS: Magnesium Sulfate monohydrate [14168-73-1]
CAS: Magnesium Sulfate heptahydrate [10034-99-8]
CAS: Magnesium Sulfate dried [15244-36-7]
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
