Determination of equilibrium constants for a number of metal‐phosphate complexes

Many metal ions form soluble complexes with pyro‐ and tripolyphosphate. Complex formation entails a decrease in pH. By measuring the pH and in some cases the concentration of free metal ions, equilibrium constants for a number of metal‐phosphate complexes were determined at 25° and at 40°. Activity corrections were applied. The tendency to form complexes increases in the following order: Tripolyphosphate has somewhat stronger complexing properties than pyrophosphate. The influence of the temperature is in most cases small. Constants obtained are listed in Table V.