Anomalous velocity change of surface wave near the gelation point

We studied the properties of surface waves during the gelation process of t ungstic acid and gelatin and silica gel by the time resolved surface wave m easurements. The anomaly is clearly shown in the change of the wave number exponent x (omega similar to k(x), the values 1.5 and 1.0 indicate surface tension and elastic wave, respectively). x of the tungstic acid was about 1 .4 in the sol state and rapidly decreased to 1.0 at the gelation point. x o f gelatin was about 1.4 (same as tungstic acid) in the sol state and decrea sed gradually after the gelation point. On the other hand, x of silica gel remained near 1.5 after the gelation point. (C) 1999 Elsevier Science B.V. All rights reserved.