the K20 glasses. Except for the 10% dolomite lime glass containing 2% LizO, which has tridymite as its primary phase, all thc Liz0 glasses have primary phases not identified by this laboratory.(2) decrease in the expansion coefficient.increase in the expansion coefficient.
(3) Deformation PointThe substitution of KzO for NazO increases the deformation temperature in all cases; the magnitude of the increase varies directly with the CaOaMgO content.The substitution of Liz0 for NazO causes a pronounced decrease in the deformation temperature in both series. Coefficient of €xpansion (70" to 160°C.)The substitution of KzO for Na20 causes a moderateThe substitution of Liz0 for NazO causes a substantial ( A ) ( B ) (4) viscosity ( A ) The substitution of KzO for Na20 increases the viscosity throughout the given range in each of the three series. The magnitude of this increase is greatest a t the lower viscosities. Increase in viscosity due to this substitution is greater in the glasses containing 16% CaO.MgO than in those containing 12%. In both series, substitutions of LizO for NazO cause substantial reductions in viscosity throughout the given range.
(5) Resistance to Attack by Disfilled Water and by DiluteThe substitution of K20 for NazO improves resistance to attack by distilled water in all cases.The resistance to attack by dilute acid is improved markedly by the substitution of KzO for NazO in each of the three series.(C) The substitution of Liz0 for NazO results in a moderate decrease in resistance to attack by distilled water in both series.(D) In the 10% dolomite series with 16% total alkali, the first 2% of Li20 substituted for Na20 has a negligible effect on the resistance to dilute acid, but further substitution results in an accelerated decrease. In the 12% dolomite series with 14% total alkali, the first 4y0 of LizO substituted for NazO has a negligible effect on the resistance to dilute acid, but further substitution causes a decrease in resistance.
( B )
Acid
( A )The highly symmetrical S042-group is not easily distorted and consequently does not lend itself readily to glass formation, Vitreous sulfates of cations of the noble-gas type are unknown.However, by combining a large cation with a weak positive force field (K+) with the strong field of the proton (H+), it became possible to distort the sulfate group sufficiently to delay crystallization on cooling and to obtain a potassium hydrogen sulfate glass.HE ability of a compound to form a glass on cooling from its liquid state depends on (1) the rate of cooling, (2) the T activation energy needed to rearrange the constituents into a structure of long-range order, and (3) the difference between the free energy of the supercooled phase and the free energy of the crystalline phase. The last represents the driving force for the transition of the glass into the crystal. If the rate of cooling is extremely high, that is, if the quantity involved is of microscopic dimensions, many salts can be obtained in vitreous condition which ordinarily would not be con...
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