The Chemical Compositions of Crystals and Glasses of the NaPO3–Na2SiO3 and NaPO3–SiO2 Systems

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Abstract
Crystals and glasses of the NaPO3–Na2SiO3 and NaPO3-SiO2 systems with various P/Si ratios have been prepared from sodium metaphosphate, silicon dioxide, and sodium carbonate. The samples with P/Si ratios in the range from 0.05 to 4.00 have been obtained as crystalline substances containing amorphous substances, while those with P/Si ratios in the range from 6.00 to 200 have been obtained as glassy substances. By the X-ray diffractometry and the paper chromatography, it has been revealed that the crystals of neither system contains any P–O–Si linkages. By the paper chromatography and the pH-titration method, it has been disclosed that the glassy substances of either system with P/Si ratios higher than 6 are hydrolyzed to give mixtures of polyphosphates when dissolved in water. The lower the P/Si ratio, the more shorter chain polyphosphates are formed. The variation in the average chain length of the polyphosphates with the P/Si ratio indicates that these glassy substances are condensed phosphate-silicates containing P–O–Si linkages. Three structural types of P–O–Si linkages have been proposed for the condensed phosphate-silicates.