SOLUTIONS OF ALKALI SOAPS AND WATER IN FATTY ACIDS .2. DENSITY AND VISCOSITY MEASUREMENTS

The investigation of the density and viscosity of the L2 solutions has yielded the following information on the structure of these solutions. Sodium caprylate reacts with caprylic acid to give an acid caprylate dissolved in caprylic acid. The acid salt formed in water-free caprylic acid has the composition 1 NaC8·2 HC8. In the presence of water 1 NaC8·3 HC8·x H2O is formed first; then as the ratio of caprylic acid to sodium caprylate decreases, the composition of this acid soap changes, apparently first to 1 NaC8·2 HC8·x H2O and then further in the direction towards a composition of 1 NaC8·1HC8·x H2O. In the water-free solutions the acid salt occurs as spherical particles, and this is the case also for the first mentioned hydrated acid soap. The water of the hydrated acid soaps appears to be firmly bound, at least up to a water content of about 5-8 moles per mole of caprylate. The same structure, consisting in hydrated acid soap dissolved in caprylic acid occurs in the narrow salient of region L2 up to a water content of about 40-50 per cent, where the composition of the acid soap is about 1 NaC8·2 HC8·x H2O. When the water content of the system exceeds the stated value, however, the structure of the solution undergoes a change, and common free" water appears in the solution; the experimental results support the conception of the formation of a solution with aggregates of sodium caprylate and caprylic acid dissolved in water. © 1969 Dr. Dietrich Steinkopff Verlag."