License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Weigh 12.3 g ±0.1 of magnesium sulfate heptahydrate (MgSO4·7H2O), and add it to a 100 mL measuring cylinder.
Add ~40 mL of milliQ water.
Add a clean stirring magnet, and leave it on a stirrer until all crystals are dissolved.
Remove the stirring magnet: To prevent touching the solution, use another magnet from the outside of the measuring cylinder to slide the stirring magnet out of the cylinder.
Fill up to 50 mL with milliQ water
Filter-sterilize.
Store at 4°C.
We usually use it without problem for up to at least a year after preparation.