Evolution of the 2-dimensional intensity distribution of the scattered lights from gelling tungstic acid

A conventional system for light scattering measurements utilizing a laser, a TV camera and a frame memory was constructed in order to investigate the gelation process of tungstic acid. The results revealed marked changes in the 2-dimensional intensity distribution of the scattered lights at about 3600 s and 5000 s after ion exchange in the present experimental conditions ([Na₂WO₄] =0.76 mol/l, 296 K). By the tilting test, it was confirmed that the first characteristic time corresponded to the gelation time, around which a marked intensity increase at the position corresponding to the laser beam was observed, while at around 5000 s, the increase occurred mainly on the outskirts of the beam, probably because of the progressive densification in the network structure. Moreover, a close correlation between the scattering characteristics and the gelation process is suggested from the numerical data.