[elisa]

Hello everyone,
I have a problem with potassium phosphite commercial formulation. Usually, the label of these products indicates:
30 % P₂O₅
20 % K₂O
They are obtained by dissolution of phosphorous acid in water and potassium hydroxide:
H₃PO₃ + KOH —> KH₂PO₃ + H₂O
KH₂PO₃ + KOH —> K₂HPO₃ + H₂O
I would like to find the initial concentration of H₃PO₃ used to obtain the concentration reporte in the label C of the commercial products. I think that:
in P₂O₅ the percentage of elemental P is 43.64 %, so starting from a solution 30 % P₂O₅ the real concentration of elemental P is 13.09 %.
In H₃PO₃ the percentage in weight of P is 37.77% so, starting from 13.09% I will obtain 34.66% H₃PO₃.
Is it right for you? Thank you for your answers,
Elisa