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 Pressure
From 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 Autoclave
It 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.