Abstract
The improved trimethylsilylation method reported previously was used to measure variation in the distribution of silicate anions in lead silicates on heating glassy samples with various molar ratios (PbO/SiO2=4, 3, 2, 1.5 and 1) at various temperatures. By combining the above results with IR and X-ray powder data it was possible to determine the type and the amount of silicate anions in the various known lead silicate compounds which were produced during crystallization.
Results of these experiments are summarized as follows:
(1) During crystallization of 4PbO·SiO2 glass the formation of the γ- and α-4PbO·SiO2 compound was observed, and the former consisted mostly of Si2O76− and SiO44−, and the latter comprised mainly SiO44−.
(2) Heat-treatment of 3PbO·SiO2 glass produced two known modifications, phase P and Pb3SiO5, designated by Smart et al., and the former was mainly composed of Si2O76−, SiO44− and polysilicate anion, the latter containing mostly Si2O76−.
(3) During crystallization of 2PbO·SiO2 glass the production of various modification forms (T-, M1-, H-Pb2SiO4) was recognized. In T-Pb2SiO4 Si2O76− prevailed, M1-Pb2SiO4 contained predominantly Si4O128− ring and H-Pb2SiO4 was composed of polysilicate anion.
(4) Heat-treatment of 3PbO·2SiO2 glass produced phase X0, whose structure was found to be different from that of barysilite obtained from undercooled melts.
(5) Heat-treatment of PbO·SiO2 yielded L(low)-PbO·SiO2 and Alamosite, which were considered to be composed of highly polymerized silicate anion, because the trimethylsilylated derivatives could hardly be detectable gas-chromatographically.
