HYDRATION OF ALUMINIUM OXIDE SOLS

Hydration of micelles in the case of aluminium oxide sols may be obtained by studying the distri­bution of ammonium ion across a semipermeable membrane. After allowing for the membrane-equili­brium effect, calculated indirectly, it has been found that 25.2 moles of water per mole of aluminium oxide are present in the micelles. An alternative method of obtaining hydration is to determine visco­sity at low concentration, calculate hydration according to Einstein's equation and to extrapolate the hydration values so obtained to zero concentration of aluminium oxide. Both the methods provide results of the same order.