# Solution of magnesium sulfate?

1. Oct 9, 2015

### HarryA

I would like to make a solution of magnesium sulfate (MgSO4) that is 15%
magnesium sulfate by mass in water. As magnesium sulfate is sold as epsom salts which is
MgSO4 7H2O I need a way to calculated the epsom salts required for the required
magnesium sulfate or 1.24 pounds per gallon of water (Water at 8.35 pounds per gallon).

I am thinking one goes by atomic weight?
For MgSO4:
Mg= 24.3 S= 32.06 Oxgen4= 4* 16 = 64 MgSO4= 120.36

For 7H2O:
7H2 = 7*1*2 = 14 7Oxgen = 7* 16 = 112 7H2O= 126.0

For MgSO4 7H2O= 120.36 + 126.0 = 246.36

So to get 1.24 pounds of MgSO4: 1.24 * 246.36/120.36 = 2.05 pounds perhaps?

2. Oct 9, 2015

### Bystander

Check.
Check.
Check.
Not check.
Take another swing at the proportion. You'll also want to account for the mass of water you're adding as hydrate.

3. Oct 10, 2015

### HarryA

Thanks.
So the ratio of water in epsom salts is: 126.0/246.36 = 51.14 % by weight and
48.86% MgSO4. So 48.86% of what weight of epsom salts is 1.24 pounds of MgSO4?
Epsom salts = 1.24/0.4886 = 2.54 pounds ?

I need to fill my RC blimp envelope with hydrogen.