mean molecular weight of the liquefied solution were determined to be as follows ______________________________________sio sub 2 concentration 8 4 k concentration 0 076 limiting viscosity 0 29 100 ml g mean molecular weight about 280 000 g mol ______________________________________ by combining the polymerized silicic acid obtained in example 3 with three different metal salts ferric chloride ferric nitrate and ferric sulphide twelve samples of flocculants having a total concentration of effective components sio 2 fe 2 o 3 of 10 0 12 5 15 0 or 17 5 were prepared as follows the solution of polymerized silicic acid prepared in example 3 was divided into twelve samples samples 1 through 12 to each sample distilled water and metal salt were added that is ferric chloride was added to four samples of a first group samples 1 to 4 ferric nitrate was added to four samples of a second group samples 5 to 8 and ferric sulphide was added to four samples of a third group samples 9 to 12 so that the mol ratio of si fe in each sample was 3 1 the solution of polymerized silicic acid obtained in example 5 was divided into three samples samples 13 to 15 to each sample was added distilled water and a different metal salt that is sample 13 ferric chloride sample 14 ferric nitrate and sample 15 ferric sulphide so that the mol ratio of si fe and the total concentration of effective components sio 2 fe 2 o 3 in each sample was 3 1 and 10 respectively three samples for comparison were prepared by using a highly polymerized silicic acid.