Guest,

Read this Wiki article to understand better:

http://en.wikipedia.org/wiki/Water_of_crystallization

Dear Guest,

May I understand well you? You have got MgSO4 * 7 H2O but you need to calculate waterless form (MgSO4)? If your answer is yes follow this calculation:

Molecular weight MgSO4*7 H2O: 246,3 g/mol

Molecular weight MgSO4: 120,3 g/mol

If you have to make 'x' g/litre (g/dm3) MgSO4 solution but you have got only MgSO4*7 H2O form you must weight from it (MgSO4 * 7 H2O) 2,0474*'x' grams every litre of solution. {2,0474=246,3/120,3}

Have a nice day!

PS: If the MgSO4*7 H2O flows in the bottle (or looks like a wet crystals) don't use it. Order a new one, pleas.

PS2: If I misunderstood your problem I apologize to you. My English is not so powerful.

I would agree with znpyro. I'm assuming also that you need to prepare an aqueous solution of magnesium sulfate and the formula you have on hand calls for anhydrous magnesium sulfate. If you need to use hydrated magnesium sulfate, you will need to account for the water of hydration when you weigh it out to prepare your solution. Molarity stays the same, but molecular weights are different. Hope I'm understanding your question correctly.

Hi Guest,

If you have been given the Magnesium Sulphate in Hydrous form, what are you testing for? I presume you have to dry it and then weigh it to calculate the previous water content?

MSM: Info below.

http://en.wikipedia.org/wiki/Methylsulfonylmethane

Magnesium tarnishes slightly in air, and finely divided magnesium readily ignites upon heating in air and burns with a dazzling white flame. Normally magnesium is coated with a layer of oxide, MgO, that protects magnesium from air and water.

So take care when drying!

'pyro' seems to have given you a pretty good explanation. But you can always look at these sites to see how and perhaps why it needs testing in the first place. BTW.

The Mole weight of Mg stays the same whether hydrous or anhydrous.

http://www.webelements.com/magnesium/

Take care.

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