An electrochemical study of some lead-polyphosphate systems
Fariss, Robert Elwyn
Doctor of Philosophy
A method for the interpretation of irreversible polarographic waves is given. The complex Pb(P2O7)2 has been identified polarographically. The dissociation constant for the complex was found by polarographic and potentiometric studies to be 2 x 10-11. A potentiometric titration study of water solutions of the glasses, sodium hexametaphosphate and sodium quadraphosphate, and of the crystalline forms, sodium pyrophosphate and sodium tripolyphosphate, is given. The precipitate, Pb2P2O7, was observed and the solubility product found to be 1.5 x 10-16. The potentiometric behavior of the quadraphosphate glass in solution was found to be distinctly different from that of a mixture of the same composition but prepared from solutions of sodium pyrophosphate and sodium hexametaphosphate. A close similarity exists between the potentiometric titration curves of the quadraphosphate glass in solution and a mixture of the same composition formed from separate solutions of sodium tripolyphosphate and sodium hexametaphosphate. The potentiometric data indicates the possible existence of the precipitate Pb(Pb2P3O10)2.