68 Science Research Writing Th en 0.1 M HCl was gradually added to the solutions, until a water to TEOS molar ratio of R = 2 was attained. Additional deionised water was added to give solutions with R = 3, 4 and 5, so that for all solutions the molecular ration TEOS:HCl was maintained, as summarised in Table 1. Th e solutions were placed in the refl uxing bath immediately aft er mixing, and the temperature of the bath was increased to 70°C in 15 min, while stirring, and kept there for
Chapter 56