On 27/5/03 9:03 am, "Max Wright"
wrote:

16.5% magnesium oxide


On Tue, 27 May 2003 11:53:42 +0100, Ednews wrote:

magnesium sulphate 100%


The first is a formal (or equivalent) analysis, the second the
actual analysis, but I'm pretty sure they are in full agreement
and describe precisely the same substance.


Nutrients in fertilizers are not reported directly, but as if
they were in a certain state of chemical combination. This allows
comparison of, say, the phosphorus content of different
fertilizers regardless of the actual state of chemical
combination of the phosphorus in them. For magnesium it would
appear that the reference state is sometimes anhydrous magnesium
oxide, MgO.

The difference between the two percentage figures is due to the
presence in epsom salts of sulfur and additional oxygen atoms,
plus water of crystallization, relative to pure anhydrous
magnesium oxide. These have the effect of "diluting" the content.

MgO = magnesium oxide

MgSO4 + (H2O)n = magnesium sulfate, or epsom salts.




--
Rodger Whitlock
Victoria, British Columbia, Canada