Long-Chain Polyphosphates

Abstract

The highly polymerized type of anion found in what we denote as long-chain polyphosphates,has a formula approximating (PO₃) _n ^n-. Sometimes, these anions are considered as having terminal OH groups and thus a formula (H₂P _n O³ⁿ⁺¹)^n- Long-chain polyphosphates have been the subject of a great number of physical investigations, mainly devoted to the estimation of their degree of polymerization. From these studies, which we do not report here, one arrives at the following two conclusions:

• (a) The degree of polymerization is very high. Molecular weights estimated by various methods, such as sedimentation, dialysis, end-group titration, viscosity, and pH titration, can vary from 500,000 to several million.

• (b) For a given compound, the values so obtained are mainly dependent on the thermal history of the specimen and on its stoichiometry. A very small departure from the theoretical O/P ratio of 3 can induce large variations in the degree of polymerization.