在較广的pH范围內,测定氟离子对硅酸(酸化的水玻璃和单硅酸鈉)胶凝作用的影响。在中性和微碱性溶液中,氟离子促进硅酸胶凝,而且这作用随所加氟离子数量而加大。在酸性溶液中,氟离子也有促凝作用,并随氟离子增多而增加。但只增加到一定限度,过此限度,促凝作用卽行減退。所生凝胶的离浆溶液合氟量亦已测定。在碱性溶液,氟离子全部在离浆液中,表示氟离子不参加凝胶的組成而仅起催化作用。在酸陸溶液,氟离子全部或大部分在凝胶內,这表示它不仅参与反应而且是产物的組成部分。根据以前所提硅酸聚合的机制,对所观測到的結果作初步的解释。 The effect of fluoride on the gelation of silicic acid (acidified water glass and sodium monosilicate) was determined over a wide range of pH. Fluorine ions promote the gelation of silicic acid in neutral and slightly alkaline solutions, and this effect increases with the amount of fluoride ion added. In acidic solution, fluoride ions also have procoagulant effect, and increased with fluoride. But only increased to a certain limit, beyond this limit, procoagulant effect diminished. The gel from the pulp solution combined fluorine content has also been determined. In alkaline solutions, fluoride ions are all in the slurry, indicating that the fluoride ions do not participate in the composition of the gel but only act as a catalyst. In acid land solutions, all or most of the fluoride ions are in the gel, which means that it is involved not only in the reaction but also as an integral part of the product. According to the previously mentioned mechanism of silicic acid polymerization, the observed results are tentatively explained.