贮放时间对钠水玻璃各硅酸存在形式及分布的影响

用三甲基硅烷化 -气相色谱法测定了经不同时间贮放的钠水玻璃的单硅酸和各低聚硅酸的含量。结果表明 ,水玻璃中各种硅酸的含量分布与n(SiO2 ) /n(Na2 O)有关。当n(SiO2 ) /n(Na2 O) =3.5时 ,随着贮放时间增加 ,单硅酸和高聚硅酸的含量同时增加 ,其中单硅酸的增加量来源于各低聚硅酸的解聚反应 ,而高聚硅酸的增加量则来源于立方八硅酸的缩聚反应。当n(SiO2 ) /n(Na2 O) =1时 ,贮放过程中无论是低聚硅酸还是高聚硅酸都只发生解聚反应 ,结果使单硅酸含量增加。当n(SiO2 ) /n(Na2 O) =2时 ,各种硅酸的变化情况较为复杂 ,贮放过程中各低聚硅酸同时发生解聚反应和缩聚反应 ,结果使单硅酸和高聚硅酸的含量同时增加 ,各低聚硅酸含量都降低。生产中实际使用的水玻璃是最接近n(SiO2 ) /n(Na2 O) =3.5的试样。

The Influence of Storing Times Upon the Contents of Different Silicic Acids for Sodium Water Glasses

The contents of the monosilicic acid and the different oligosilicic acids for the water glasses storing at different times has been determined by trimethylsilylation gas chromatograph. Results showed that the contents of the different silicic acids relate to n (SiO 2)/ n (Na 2O). When the n (SiO 2)/ n (Na 2O)=3.5, the contents of the monosilicic acid and the contents of the high polysilicic acid both increased with the storing times. The increment of the monosilicic acid stemmed from depolymerization of the different oligosilicic acid, and the increment of the high polusilicic acid originated from polymerization of the cubic octasilicic acid. When the n (SiO 2)/ n (Na 2O)=1, both of the monosilicic acid and the high polysilicic acid only generated depolymerization, so that the contents of the monosilicic acid increased. When the n (SiO 2)/ n (Na 2O)=2, the changes the content of the different silicic acids was more complicated. The different oligosilicic acids both generated depolymerization and polymerization, so that the contents of the monosilicic acid and the high polysilicic acid both increased, however, the contents of the different oligosilicic acids decreased. The water glasses used in industry was closed to the sample of n (SiO 2)/ n (Na 2O)=3.5.