STUDIES ON CHEMICAL COMPOSITIONS AND WATER SOLUBILITIES OF GLASSES, IV

Abstract

In the present communication, the present authors report the further results of studies, continuing the previous reports (This Journal, 1934, 42, 399; 1935, 43, 719; 1936, 44, 143), on the effects of alumina Al2O3, magnesia MgO and boric oxide B2O3 to the water resistibility of ordinary soda-lime glasses of window glass, plate glass, rolled glass, etc. The following is the brief abstract from the original Japanese paper.(1) As a standard glass of ordinary soda-lime glass type, was prepared the glass sample signed SCN-O, containing silica SiO2 72%, lime CaO 13% and soda Na2O 15% as constant as possible.(2) This 13% of lime CaO was displaced by 3% alumina Al2O3 from potash feldspar or kaolin, 3% by 2% magnesia MgO from dolominte or 6 (3+3)% from both of them, and 72% silica SiO2 was displaced boric oxide B2O3 from borax. These natural raw materials, i.e., silica sand, potash feldspar, kaolin and dolomite, have the following chemical compositions.Table 1-Chemical Compositions of Natural Raw Materials(3) Using these chemicals and natural raw materials, batch mixtures were made, melted in chamotte crucible in gas furnace, by displacing lime by alumina, magnesia or both of them and silica by boric oxide in the amount of 2, 3 or 6% as above described. 9 samples of test glasses were thus obtained and their chemical composition were analysed shown in the following table 2.(4) Samples of one sheet glass and two mould glasses were obtained from the market and used for the comparison in the present study. Their chemical compositions were analysed and compared with those of test glasses.(5) These 12 glass samples were compared on their chemical compositions and specific gravities in the following table 2.It is sorry that the chemical compositions of 9 test glasses deviated a little from the standard, owing to the impurities in the natural raw materials, from the melting chamotte crucibles, etc. The sign W shows the samples obtained from the market, and window or sheet glass WII and mould glasses WI and WIII. Some of these 9 prepared and 3 market glass samples have quite equall chemical compositions and specific gravities.Table 2-Chemical Compositions and Specific Gravities of Glasses(6) These glass samples were ground and grains of dia. 0.49-0.75mm were obtained by sieving and remaining between 64 meshes/cm2-sieve and 144 meshes/cm2-sieve. These grains were washed with alcohol and dried, and then tested on their solubilities in boiling water of (1) the atmospheric pressure, (2) 5 atm. pressure of steam papour, and (3) 10 atm. steam pressure, in silver gauze suspended in silver beaker or crucible. The water solution was titrated by N/50-H2SO4 solution and the amount of dissolved alkali was calculated, the weight decrease of glass grains was weighed, and then the ratio of these amounts of dissolved alkali and weight decrease was compared, as quite equally adopted in the foregoing reports. Some results are tabulated in the following tables 3 and 4.Table 3-Comparison of Water Solubilities of Various Glass Samples under Atmospheric Pressure tested by the Grain MethodThe following points are seen from these results, that (1) displacement of CaO by 3% MgO is not effective to the water resistibility of glass, (2) displacement of CaO by 3% Al2O3 is remarkably effective, (3) displacement of SiO2 by 2% B2O3 is not effectve, (4) MgO and B2O3 are to be effective to lower the viscosity of molten glass metal at the working temperature, (5) window or sheet glass and mould glasses on the market are a little inferior in water resistability, owing to the insufficient amount of Al2O3, etc.Table 4-Comparison of Water