Preparation of 1M Magnesium Sulfate (MgSO4) Stock Solution

Overview

Magnesium sulfate (MgSO4) is soluble in water. Magnesium sulfate is available in anhydrous as well as hydrated forms. Since anhydrous Magnesium sulfate is highly hygroscopic (quickly absorbs water from the air), it is difficult to weigh it accurately, therefore, is not used for preparing solution. Magnesium sulfate heptahydrate (MgSO4·7H2O, Mol Wt: 246.47) is quite stable and often used for the preparation of 1M Magnesium sulfate solution.

A 1M stock solution can be prepared by dissolving 24.6.47 g of  Magnesium sulfate heptahydrate (MgSO4.7H2O, Mol Wt: 246.47) in water to a final volume of 1000 ml.

REQUIREMENTS

Reagents and solutions
Magnesium sulfate (MgSO4.7H2O)
Deionized / Distilled water

Equipment and disposables
Measuring cylinder
Conical flask / Beaker

Composition
1 M Magnesium sulfate

Objective
Preparation of 100 ml 1 M Magnesium sulfate

PROCEDURE

Step 1: To prepare 100 ml of 1 M Magnesium sulfate, weigh out 24.647 g Magnesium sulfate heptahydrate (MgSO4·7H2O, Mol Wt: 246.47) in a 250 ml conical flask/beaker. Add 800 ml deionized/Milli-Q water and mix until dissolved completely. 

Tip:
One can use manual shaking using a glass pipette to mix the ingredients. Magnetic stirrer makes the dissolving process easy and convenient.

Precaution:
Do not dissolve in 100 ml of deionized / Milli-Q water. In most cases, solution volume increases when a large amount of solute is dissolved in a solvent.

Step 2: Adjust the volume to 100 ml with deionized / Milli-Q water. Mix it again.

Step 3: Sterilize the solution by autoclaving (20 minutes at 15 lb/sq.in. (psi) from 121-124°C on liquid cycle).

Note:
The solution can also be sterilized by filtering it through a filter unit containing a membrane with a pore size of 0.22µm or less under sterile conditions.

Storage
The solution can be stored in the cold room.