The Structure and Constitution of Glass
JSGT 1942 V26 T082-T107
Some consequences are considered of the conclusion that in viscous silicates four oxygen atoms are attached to a silicon atom forming a tetrahedral unit, which is the fundamental unit of structure in glassy as well as in crystalline silicates. It is pointed out that there are certain reservations, as yet incompletely considered, attaching to the random network theory, for as the concentration of silica decreases the minimum particle size completely satisfying all the requirements of ratios of silicon, oxygen, and metal atoms decreases also until at 33.3 molecular per cent silica individual tetrahedra must exist. A preliminary attempt is made to correlate this decreasing particle size, or co-ordination group, with known physical and chemical properties of glasses. It is suggested that before a harmonious theory of the constitution of glasses can be sot out much more requires to be known of the constitution of simpler solutions, and that X-ray investigations on glasses have to some extent gone ahead of this vitally necessary preliminary work. The persistence of the SiO4 tetrahedra in glassy silicates is the significant fact which emerges from the X-ray investigations, and on this simple result alone a plausible explanation is afforded of many of the properties of glasses. The problem of the manner of bonding of the metal atoms is much less certain and requires further research.
Eric Preston, Ph.D., D.Sc., F.I.C., F.Inst.P.
