Sodium Metabisulphite Dosing Calculator
SMBS is dosed against one of two things: the chlorine it has to neutralise, or the sulphite level it has to hold in the water. Those are different design bases and the two answers are not interchangeable, so the basis is yours to choose. The stoichiometry itself is exact and needs no supplier data — one mole of SMBS reacts with one mole of chlorine, and one mole of SMBS yields two moles of sulphite. The chlorine residual and the product strength are the inputs, because they are measurements.
Design parameters
Choose the basis first, then supply the figure that basis is measured against. Nothing is filled in for you: there is no default chlorine residual and no default product strength.
Basis and limits
- The two bases are never added together. A dechlorination figure sizes the dechlorinator; a sulphite figure sizes the feed protection, and a plant needs whichever its process calls for.
- Where the certificate assay and the nominal strength differ, the assay is the measured fraction and the nominal strength is only a label. The assay is used on its own.
- SMBS above the demand adds sulphite that the membranes do not remove; it is carried into the brine. Overdosing is not conservative.
- No finished pH is predicted. The pH after dosing comes from the dose, the alkalinity and the buffer in the water, so measure it.
Workspace
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