Understanding Equilibrium formula

Discussion in 'Water Chemistry' started by Henrik, 4 Dec 2008.

  1. Henrik

    Henrik Member

    Chester, Cheshire
    Hi there,

    I have tried to calculate the percentage of magnesium, calcium and potassium sulfates that need to go into Equilibrium to reach the percentages stated on the website (forgetting about the small Mn anf Fe sulfate amounts). I do not seem to be able to quite figure it out, as the amounts of the different sulfates needed to make 1000g of my equivalent mix (based on providing the given percentages of each element) add up to about 1025g...The logic was such - Equilibrium contains 19.5% K, I get 44.88% K from KSO4, thus I need 434.54g KSO4 to provide 195g K in a 1000g mixture (19.5%), and so on for MgSO4 and CaSO4.

    I know that this tiny difference is utterly irrelevant, but I would also like to get my understanding of dry powder usage right (you guys got me interested in the chemistry!). Am I making a mistake here somewhere in the calculations?

    Many thanks, Henrik
  2. plantbrain

    plantbrain Expert

    The chemical fertilizer lingo from the USA is archaic. The % is fine, but often they will use things like KO2 for K+ rather than just K+ ppm or %.

    Basically, I add about 1/2 K2SO4, 1/3 MgSO4 and the 1/6th left as CaSO4.
    You can use calculators to figure out how much ppm those add. Add say 5 grams to every 1 kg for the Fe and about 2 grams for the Mn.

    Be careful.............many calculators do not include the water in the salts, salts absorb water very well and "cake", turning into bricks. Epsom salt is MgSO4 * 7 H2O, the seven H2O's clearly can make a large difference..........

    We use this as buffer for higher K+ and for Mg and lesser for Ca.
    So the actually amounts are not that critical, rather, it's used to bump them up and provide non limiting values for GH and K+.

    You can store the GH booster with Rice to remove the moisture or a silica gel dessicant etc.

    Tom Barr

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