In an earlier paper the preparation and physical properties of boron litharge cements were reported. (
J. Ceram. Assoc. Japan,
71 [7] 135-40 (1963)).
This study was carried out to investigate the solidifying mechanism of boron litharge cements. The process of reactions was observed microscopically and reaction products which seem to participate in the solidification were separated purely and studied by means of X-ray diffraction, infra-red spectra, chemical analysis and so forth.
From these results, it was assumed that the solidifying mechanism consists of two kinds of reactions. The one is the crystal growth reaction from glycerol-liharge system. Needleshaped crystals with the composition C
3H
6O
3Pb growing radially from litharge crystals, seem to play a part in the soldification by intertwining. The other is the formation of glassy substance from glycerol-boric acid-litharge system. This material is colorless and transparent and has so strong binding force that seems to combine unreacted excess litharge tightly. In low boron specimens both of two mechanisms seem to contribute to solidify the cement, but in high boron specimens so crystal growth is observed. Physical properties of boron litharge cements seem to be affected by the degree of participation of the two mechanisms.
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