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Alkalimetric titration of phosphoric acid and phosphates

1949; Royal Netherlands Chemical Society; Volume: 68; Issue: 1 Linguagem: Inglês

10.1002/recl.19490680107

1878-7096

J. C. W. Dijksman,

Chemical Synthesis and Characterization

Abstract Many contradictory data are known concerning the alkalimetric titration of phosphoric acid. The uncertainties, which have received a solution in this investigation, concern: the correct titration exponent in titration to mono or diphosphate; the correct composition of crystalline disodium phosphate which turned out to be exactly Na 2 HPO 4 . 12H 2 O; the inflexion points in the titration curve were found to coincide with the equivalence points. Further a search was made for a suitable and accurate method of carrying out an alkalimetric phosphate determination in phosphates containing calcium, aluminium and iron, because the known methods are all unreliable. A removal of the disturbing metallic ions with the aid of a cation exchanger was found to be the solution. An attempt was made, but without ultimate success, to exclude disturbing fluoride and silicofluoride. The demands, which must be made in alkalimetric titrations on the purity of distilled water, have been sorted out and summarised.