The existence of polymeric complexes in dilute solutions of aluminium and orthophosphate

Summary The presence of soluble polymeric complexes in dilute solutions (10–30 M) of aluminium and phosphate at 25°C was demonstrated by paper electrophoresis and confirmed by chemical analyses and measurements of ³² P specific activities. Complexed aluminium and phosphate were not determined by colorimetric procedures without preliminary hydrolysis in 1 N HCl at 80–90°C. The formation of aluminophosphate complexes was maximal around pH 5 when, at an initial P/Al mole ratio of 1.6, 3 moles of P were complexed with 4 moles of Al. At pH 6.9, however, only 1 mole of P was removed for every 10 of Al, suggesting that hydroxyaluminium polymers predominated at higher ratios of OH-ions to H₂PO₄-ions. re]19750523