BS 4427-6 – Methods of test for sodium tripolyphosphate (pentasodium triphosphate) and sodium pyrophosphate (tetrasodium pyrophosphate) for industrial use
Potentiometric method after conversion of the tetrasodium pyrophosphate to disodium dihydrogen pyrophosphate and precipitation of the pyrophosphate with liberation of sulphuric acid. Applicable to products containing at least 90 per cent of tetrasodium pyrophosphate and in the absence of more condensed forms of phosphate.
