Experimental data on the density, d, and viscosity, η, of ammonium oxalate aqueous solutions in the range of undersaturation and supersaturation are reported for solutions of saturation concentrations, c s , between 0.36 M and 0.75 M. It was found that the temperature dependence of d for solutions of different saturation concentrations may be described by a first-order equation while that of η may be described by an Arrhenius-type relation. Moreover, for solutions of particular saturation concentrations, c s , both d and η linearly increase with supersaturation.

Density d, surface tension γ, and refractive index n of ammonium oxalate aqueous solutions of concentrations up to saturation have been measured in the temperature range between 293 K and 333 K. The results of d, γ, and n are fitted as functions of solution concentration. It was found that the first- and second-order equations relating these quantities with solution concentration can satisfactorily be used to describe the data.

The experimental data of the temperature and concentration dependence of viscosity of concentrated aqueous ammonium oxalate solutions are analysed using the hole theory of liquids and Einstein's model of viscosity. Analysis of the data revealed that the dimensions of the species participating in the growth of ammonium oxalate monohydrate crystals are 3-5 times larger than the dimensions of individual NH 4 + and C 2 O 4 2-ions composing them.