Studies on Chemical Compositions and Water Solubilities of Glasses, III

Abstract

On continuing the previous studies (This Journal, 1934, 42, 399; 1935, 43, 719), the present authors carried on the studies on the relation between chemical compositions and water solubility or resistibility of common soda-lime glass by replacing some parts of silica with other acid anhydride components, boric acid B2O3, titanic acid TiO2, or phosphoric acid P2O5. The main points of the present communication are briefly abstracted from the original Japanese paper, as following:Table 1-Analyses of Chemical composition of Prepared Glass Samples(1) Standard compositions of common soda-lime glass of sheet glass, plate glass, bottle glass, etc., i.e., SiO2: 72%, CaO: 13% and Na2O: 15%, were changed in the amount of SiO2, replacing by B2O3, TiO2 or P2O5 from 1-2% to 7-8%, and fixed the other two components CaO and Na2O nearly constant. These desired glass samples were prepared, by mixing the pure chemical CaCO3, Na2CO3, Na2B4O7⋅10H2O, TiO2, Na2HPO4⋅12H2O and pure silica sand, and melting the batches in chamotte crucible at 1400-1450°C of gas furnace. These glass samples were analysed and the following results were obtained, as shown in the table 1.(2) These glass samples were crushed and sieved to grains of dia. 0.75-0.49mm, i.e., passing through 64 meshes/cm2-sieve and remaining on 144 meshes/cm2-sieve. These grains were throughly washed by absolute alcohol and completely dried in desiccator. The solubility of glass in water was treated in the following two ways:(A) The first method is to heat 5g of the above prepared glass grains in silver gauze suspended in silver beaker with 200cc of distilled water for 2 hours on water bath under atmospheric pressure(B) The second is the autoclave method, i.e., 5g of the glass grains were taken in silver gauze suspended crucible with 40cc distilled water and heated for 2 hours in an autoclave under pressures of live steam of (a) 5 atm. and ca. 150-152°C or (b) 10 atm. and ca. 180-181°C.After these treatments of both methods, the water was decanted and washed, and then titrated by N/50-H2SO4 solution to determine the amounts of dissolved alkaline, and the glass grains in silver gauze were weighed to obtain the decrease of dissolved part. The (A) method is nearly equal to those of the Shefield method of English origin and the D. G. G. method of German origin (W. E. S. Turner, Bull. Amer. Ceram. Soc., 1935, 14, 168) The results were fully compared in the following tables 2 and 3.Table 2-Comparison of Solubilities of Various Glass Samples in Water by the Powder Method under Atmospheric PressureFrom these results, it is seen that the order of resistibility of glasses by the acid component is B2O3>TiO2>P2O5 in the case of replacing to SiO2 in the small amount of 2-8%.Table 3-Comparison of Solubilities of Various Glass Samples in Water by the Powder Method Heated at Higher Steam Pressure 5 or 10 Atm. in AutoclaveIt is seen from these results, that the order of resistibility to water at the higher pressure is quite equal to that at the atmospheric pressure in the table 2. But the solubilities of the glasses containing 3-8% of phosphoric acid SCN-PI, SCN-PII and SCN-PIII are remarkably increased, which is perhaps owing to the formation and separation of insoluble Ca3 (PO4)2 to the opaque glass in the presence of large amount of CaO and P2O5. The glasses SCN-Bα, SCN-Bβ and SCN-BI, containing small amounts of B2O3 0.9-2.5%, are not so good water-resistible.