Metal chelates of tripolyphosphate

Stability constants of 1 : 1 and 2 : 1 chelates of TPP with bivalent metal ions, Cu(II), Zn(II), Co(II), Mn(II), Ni(II), Mg(II), Ca(II), Sr(II) and Ba(II) are reported at 45°C and 0·10 ionic strength. The stabilities decrease in the order Cu(II) > Co(II) > Mn(II) > Zn(II) > Ni(II) > Mg(II) > Ca(II) > Sr(II) > Ba(II) for the 1 : 1 protonated complexes and for the normal 1 : 1 complexes, in the order Cu(II) > Ni(II) > Zn(II) > Co(II) > Mn(II) > Mg(II) > Ca(II) > Sr(II) > Ba(II). For the 2 : 1 protonated and normal complexes the stabilities decrease in the order Cu(II) > Mn(II) > Co(II) > Ni(II) > Zn(II) > Mg(II) and Cu(II) > Mn(II) > Ni(II) > Co(II) > Zn(II) > Mg(II) respectively. © 1971.