The Physical Properties of Glasses. Part V. A Peculiar Phenomenon in the Vitreous System Na₂O–B₂O₃ 

_{JSGT 1946 V30 T303-T305}

_{The density–concentration curve of sodium borate glasses is determined and the S-shaped curve found is discussed. At a concentration of 4% Na2O a widening of the oxygen network is found which is not connected essentially with the sudden increase of the electric conductivity at this composition.}

J. M. Stevels