Viscometric Studies of Solutions of Sodium Phosphates, Graham Salts and Vanadium-containing Graham Salts

The intrinsic viscosities of sodium orthophosphates, pyrophosphate, tripolyphosphate and Graham salts of relatively low molecular weight (lower than 10300) were measured. The relation between the intrinsic viscosity at 25.5°C and the average molecular weight measured by the end group titration was [η]=6.9×10−4×M0.61 in a 0.035 n sodium bromide solution, and [η]=0.0348+0.112×10−4×M in a 0.07 n sodium bromide solution. Vanadium-containing Graham salts (sodium vanadate-phosphate copolymers) seemed to be hydrolyzed immediately by the dissolution. The intrinsic viscosity of the solution was much smaller than that of sodium polyphosphate of the corresponding degree of polymerization. The rate of the hydrolysis of branched sodium polyphosphate was proportional to the number of branchings, and the rate constant was 0.39 hr−1 at 25.5°C.