Sulfate Decomposition and Sodium Oxide Activity in Soda–Lime–Silica Glass Melts

Reaction equilibrium constants for the sulfate decomposition process, which releases oxygen and sulfur oxide gas in soda–lime–silica glass melts, have been determined. The chemical solubility of SO₂, probably in the form of sulfite ions in soda–lime–silica melts, has also been determined. The chemical solubility value of SO₂, dissolving as sulfite, ranges between 0.02 and 0.06 wt% SO ₃ ²⁻ at 1 bar SO₂ pressure in the temperature range of 1600–1800 K. Results of square-wave-voltammetry studies and measurements of the temperature-dependent sulfur retention after the fining process of commercial float glass melts and a model soda–lime–silica melt, with 74 wt% SiO₂, 16 wt% Na₂O, and 10 wt% CaO, are presented. The measured sulfur retention data and the results of the square-wave-voltammetry studies are used to determine the equilibrium constant of the sulfate decomposition reaction in the temperature range of 1600–1800 K. The thermodynamic relations and properties found for sulfate decomposition are used to derive activities of sodium oxide in soda–lime–silica melts. Literature values for sodium oxide activities in these glass melts are rare. In this study, these activities have been determined by a method, based on the measurement of sulfate decomposition equilibrium constants and the residual sulfate concentrations in glass melts, equilibrated with almost pure sodium sulfate galls.     

Models and Experiments for Sodium Evaporation From Sodium-Containing Silicate Melts

Universal simulation models based on (a) validated mass transfer relations and (b) thermodynamic modeling procedures for glass melts are developed to predict the evaporation rates of volatile species from a large range of glass melt compositions. Depending on the glass composition, temperature of the surface of the melt, local composition of the atmosphere, exposure time of a melt layer to the combustion atmosphere, and local gas velocities above the glass melt surface, the evaporation rates of volatile species can be estimated. Laboratory-scale transpiration evaporation experiments have been used to study evaporation kinetics, to derive mass transfer relations, as well as to validate the sodium evaporation modeling results for sodium-silicate melts as well as for soda-lime-silicate melts. In these investigations, the molten sodium-silicate and soda-lime-silicate melts are exposed to atmospheres of flowing gases with controlled composition and gas flow rates. In a humid atmosphere for example, sodium mainly evaporates as NaOH. From the measured NaOH evaporation rates and the mass transfer relations, the NaOH vapor pressures in equilibrium with the molten glass at prevalent temperature and furnace atmosphere composition were derived. The NaOH vapor pressures are assumed to be in equilibrium with the glass melt composition at the surface of the melt. During the evaporation test, the Na₂O surface composition will change due to depletion. This leads to equilibrium vapor pressures decreasing with time, reflecting the changing chemical activity at the glass melt surface. The results of evaporation tests for sodium-disilicate and soda-lime-silicate glass melts are shown. Chemical activities derived from these measurements are compared with the results of thermodynamic modeling, using a method based on a glass melt from ideal mixtures of associate (stoichiometric) species of structural compounds with known thermodynamic properties.     

Behavior of Bubbles of Oxygen and Sulfur Dioxide in Soda-Lime Glass

Bubbles of sulfur dioxide are dissolved by soda-lime glass containing arsenic or ferric oxide at a rate which follows a square-root-of-time law, indicating a diffusion process. Mixtures of sulfur dioxide and oxygen are dissolved very rapidly as long as both gases are present, whereas an excess of either gas remaining in the bubbles is adsorbed at the normal rate, which depends on the composition of the glass. Apparently sulfur dioxide is dissolved by oxidation either by oxygen in the bubble or by oxygen diffusing from oxidizing constituents in the glass, whereas oxygen is dissolved by diffusing into the glass to react with reducing constituents.     

GASES IN GLASS*

An apparatus is described for extracting the gas from glass at glass-furnace temperature and determining its composition. Results are given for glasses of various compositions and various melting histories. All ordinary glasses were found to contain appreciable quantities of dissolved (or chemically combined) gas, the amount varying from a few hundredths to a few tenths per cent. Water is frequently the most abundant gas, the content being highest in borosilicate glasses. Carbon dioxide is also usually present, the amount depending on the basicity of the glass. Nitrogen, carbon monoxide, and hydrogen were never found present in appreciable quantities. All oxidized glasses contain some oxygen. Glasses containing arsenic give off a comparatively large volume of oxygen. The effect of this oxygen on fining is discussed. It has been found that remelting a glas has little effect on the gas content. The gas content is greatly influenced by the size of the melt, being the lowest in small experimental melts.     

Diffusion of Oxygen from Contracting Bubbles in Molten Glass

Some experimental measurements on the rate of contraction of oxygen bubbles in molten glass were compared with an equation for the diffusion- controlled contraction of a sphere. This comparison showed that the equation was valid until about 80% of the oxygen had diffused from the bubbles, so that the diffusion coefficient of the oxygen in the molten glass could be calculated from the experimental measurements. These values of the diffusion coefficient were higher than one would expect from the Stokes-Einstein equation for diffusion in liquids. Thus it was concluded that some short-circuiting mechanism such as diffusion in channels in the glass was operative. It also appeared that the oxygen diffused in the glass as atoms, rather than as molecules. From contraction measurements on glasses with different fining agents it was concluded that the mechanism of fining by such agents as antimony and arsenic oxides was not discharge of oxygen gas as had been generally supposed but was reduction of the concentration of oxygen in the glass, which caused the oxygen in the bubbles to diffuse into the glass more rapidly.     

硫酸盐在玻璃澄清中的若干问题探讨

阐述了硫酸盐在高温玻璃熔体中可能发生的化学反应以及硫酸盐发生热分解反应达到平衡时的平衡常数热力学表达式,讨论了硫酸盐在玻璃熔体中作为澄清剂的澄清机理,介绍了硫在玻璃基体中可能存在的价态以及影响硫在玻璃体中的含量的因素。     

Gas Solubility in Glasses: Principles and Applications

There are numerous practical applications of the solubility of gases in glass, for example, gas separation and the outgassing and leak testing of vacuum systems. Analysis of the structure of glass provides an understanding of the mechanisms of gas solution, diffusion, and permeation. The gas atoms (or molecules) serve as structural probes. Noble gas solubility in vitreous silica indicates the distribution of interstitial size to be lognormal in nature, a result confirmed by computer-generated models. In related studies, computer models have indicated that the ring statistics in vitreous silica are normal (Gaussian) in nature over a wide range of pressures. The geometrical literature on convex polyhedra provides additional detail about the nature of the structure of glass and its relationship to gas transport. This paper focuses on gas solubility in rigid glasses below the glass transition temperature, but there are implications for the related problem of gas solubility in glass melts, another problem of substantial commercial interest. The understanding of gas solubility has also had a significant influence on models of geological importance, such as volcanic eruptions and formation of the earth's atmosphere. These studies in the earth sciences, in turn, enhance our understanding of engineered glasses.     

The barrier properties of polyethylene terephthalate to mixtures of oxygen, carbon dioxide and nitrogen

The diffusion and solubility of oxygen, nitrogen and carbon dioxide have been studied in amorphous and biaxially oriented films of polyethylene terephthalate (PET). To measure the sorption and desorption of each gas simultaneously in cases where mixtures of gases were studied, a mass spectrometer was used as a detector. It was found that the solubility and diffusion of nitrogen in PET were markedly affected by the presence of the other gases, oxygen and carbon dioxide with differences in detail between results for the amorphous and biaxially oriented films. It is of particular interest that the presence of oxygen reduces the solubility and increases the diffusivity of nitrogen.     

相关组分在制造硒硫化镉颜色玻璃中的作用

在制造硒硫化镉颜色玻璃时 ,除了加入玻璃的基本组成 Si O2 和着色剂 Cd S、Se外 ,还必须加入 Zn O、碱金属氧化物、冰晶石、B2 O3和重金属硫化物等次要组分。这些次要组分在制造硒硫化镉颜色玻璃过程中起着重要作用。Zn O对防止着色剂硒和硫的挥发起直接作用 ,是制造硒硫化镉颜色玻璃不可缺少的组分之一。碱金属氧化物、冰晶石、B2 O3主要起助熔作用 ,降低玻璃熔制温度 ,加速玻璃的澄清和均化 ,间接防止着色剂硒和硫的挥发。微量重金属硫化物作为晶核形成剂 ,使 Cd S(Se)微晶固溶体容易成核和长大 ,加速并简化玻璃的显色工艺     

Physical and Chemical Solubility of Nitrogen in Glass Melts

Values for the physical solubility of nitrogen as well as for the content of chemically dissolved nitrogen in glass melts are given. The form in which the nitrogen is present in the glass melts is discussed and an attempt is made to explain chemical interaction between nitrogen and the glass melt. The dependence of the amount of physically or chemically absorbed nitrogen on the nature of the furnace atmosphere is shown. The results offer an explanation for the presence of nitrogen often observed in bubbles of commercial glasses.     

ANALYSIS OF GASES DISSOLVED IN GLASS AND GASES PRESENT IN SEEDS*

A method of analysis for gases dissolved in glass has been developed which gives more reproducible results than those previously reported. The problem of the volatilization of alkali from the sample during the course of analysis appears to have been satisfactorily solved through the use of an auxiliary furnace. A number of commercial glasses have been analyzed for dissolved gases. Water vapor, sulfur dioxide, and oxygen are the principal gases found in flint glass. Water vapor seems to be the principal constituent of the gases found in amber glass. A method for the analysis of gases present in seeds in glass has been developed which gives fairly satisfactory quantitative results on samples containing more than 1 cu. mm. of gas. The results obtained on samples containing less than 1 cu. mm. of gas are qualitative only. The procedure consists (1) in the determination of the temperatures at which gases present in the seeds undergo a change of state and (2) in the microchemical analysis of these same gases. Seeds have been found that contained entrapped air, sulfur dioxide, and also carbon dioxide. Some seeds, especially those in amber glass, appear to be vacuum seeds, and these frequently contain a deposit on the inside which has been identified as a sulfite or a sulfate.     

SELENIUM RUBY GLASS*

This paper presents the results of an experimental study on the production of selenium ruby glass, particularly on the retention of the colorants during the melting and fining operations. Selenium, cadmium, and sulfur are necessary in the final glass to get a ruby color. Reducing conditions are conducive to the retention of a large percentage of the selenium in the glass, but when conditions are highly reducing, cadmium is eliminated almost completely. The writers believe that too little attention has been given in the past to the chemistry of the entire glass batch, and as a result operators and research workers have often failed to get a ruby glass not because the loss of selenium was too high but because they eliminated the cadmium by maintaining too strongly reducing conditions. A balance must be maintained so that the batch and the atmosphere above it are sufficiently reducing to hold enough selenium in the melt but not so strongly reducing as to eliminate the cadmium. Most of the work reported in this paper was done on soda-lime-silica glasses similar to those melted in continuous tanks for the production of machine-made ware. A glass of this composition, containing 0.03% of selenium, 0.06% of cadmium, and 0.03% of sulfur, will produce a ruby color. The writers have found that if the cadmium is added as cadmium sulfide the final glass will have sufficient sulfur for color development. The use of silicon as a reducing agent is suggested. An arrested-cooling procedure for developing color is described briefly.     

Gas permeability of copolypeptide membranes composed of γ-methyl L-glutamate and γ-benzyl L-glutamate

Membranes of copoly(γ-methyl L -glutamate, γ-benzyl L -glutamate) (PMBLG) as well as the related homopolymer membranes were prepared, and permeabilities of oxygen, nitrogen, argon, and carbon dioxide were measured in the 0–70°C temperature range. The values of permeability coefficients and solubility coefficients of the copolymers were smaller than those of permeability coefficients and solubility coefficients of the two homopolymers for every gas studied. The diffusion coefficients of the gases showed a minimum at around 25 mole % benzyl glutamate. The temperature at a maximum of tan δ spectra for the membranes showed a maximum at around 25 mole % benzyl glutamate. The Arrhenius plots of diffusion coefficients and solubility coefficients for PMBLG, which contained 50 and 71 mole % benzyl glutamate, showed a break at about 50 and 40°C, respectively. This permeation behavior is explained by assuming a unique interaction between methyl glutamate and benzyl glutamate side chains.     

Mechanism of Oxygen Diffusion in Glassmelts Containing Variable-Valence Ions

A mechanism is proposed to describe the influence of redox reactions, which involve variable-valence ions, on the diffusional mass transport of molecular dissolved oxygen in glassmelts. The concentration profile for molecular dissolved oxygen in a melt with diffusional transport in one direction in a Cartesian coordinate system is described by a differential equation: ∂(O₂/∂ t = D_c (∂²[O₂]/∂ x ²), where D_c depends on the actual value of the diffusivity D of physically dissolved oxygen, the local molecular oxygen concentration, the concentration of variable-valence ions, and the equilibrium constant for the relevant redox reaction. This equation is applicable for diffusion into or outwards from the melt from or into the furnace atmosphere. It is shown here that the value of D_c is always less than D . Concentration profiles for diffusing oxygen in glassmelts with refining agents (containing variable-valence ions) are thus steeper than profiles in melts without refining agents. A decrease in temperature of a glassmelt with variable-valence ions generally leads to diffusion of oxygen into the melt. The flux of oxygen gas into (oxidation) or out (reduction) of the melt is proportional to ( D/D_c )^1/2 and is enhanced by the effect of variable-valence ions dissolved in the melt.     

Single and mixed gas diffusion through polyethylene films

In this paper, the results of using a mass spectrometer technique to measure mixed-gas diffusion through polymer films are presented. Mixtures of oxygen, carbon dioxide and nitrogen are diffused through films of polyethylene with different degrees and type of chain branching. It is shown that in the case of pure gases Henry's law applies; the gas concentration is proportional to the partial pressure of gas. It is also demonstrated that there is a reasonable correlation between gas solubilities and the Lennard-Jones force constants, although detailed departures from this behaviour are observed for the different materials.The results show that, in general, the presence of one gas can affect the diffusion and solubility of another, although the solubility and diffusion of carbon dioxide were found to be independent of other gases. In particular, an apparent competition is observed between nitrogen and oxygen in terms of solubility. Moreover, the nature of the interaction between gases depends on the degree of branching and the state of annealing of the polyethylene. Contrary to expectation, it is shown that annealing, whilst increasing the crystallinity, increases the permeability of all gases for the only two samples studied in this regard.     

Solubility of Carbon Dioxide and Variation of Oxygen Ion Activity in Sodium Borate Melts

The solubility of carbon dioxide in 38.8, 45.4, 49.7, and 54.0 wt% soda-boric oxide melts is investigated. The data are used to determine the variation of oxygen ion activity with composition and temperature. The results are compared with those obtained earlier for the system sodasilica.     

Role of Sulfur and Its Diffusion in Silicate Glass Melts

Sulfur diffusion D_S is reported on a technical alkali-poor barium alumoborosilicate glass melt at 900–1400°C and on three further Na₂O-modified glass melts at 900°C, using a radioactive tracer method. Whereas D_S for the base glass melt amounts to ≈1 × 10⁻¹⁵m²/s at 900°C, it increases nearly exponentially with increasing Na₂O content from 0 to 15 mol% by almost three orders of magnitude. Similar to other glass melts, the sulfur diffusion obtained in these melts is also closely related to the Eyring diffusivity D_n derived from viscosity. The diffusion controlling species in oxidized melts seems to be SO₄²⁻, in reduced melts S²⁻. SO₃²⁻ does obviously not play any role in this transport process.     

CO等气体在苯酚中的溶解度的测定及关联

建立了一套用于测定高中压下气体在黏度大、易结晶高黏度溶剂中溶解度的汽液平衡测定装置,该装置采用整体温浴、流动的方法很好地解决了溶剂苯酚易结晶而带来操作困难的问题,利用该套高中压汽液平衡测定装置,在不同温度和压力下,测定了CO₂、CO、N₂、O₂气体在纯苯酚中的溶解度数据.采用RK方程的维里展开式和正规溶液理论推算得到的气体溶解度与温度和压力的函数关系式,并对相同温度和压力下CO等气体在纯苯酚中的溶解度进行了三参数关联,得出了溶解度的计算模型.最后,用这一模型关联计算CO₂、N₂、O₂和CO在纯苯酚中的溶解度,结果表明,计算值和实验值误差较小,因此,该计算模型可以用于对相同温度下加压气体在纯苯酚中溶解度的关联和内插计算.     

高硼硅玻璃的复合澄清剂研究

介绍了高硼硅玻璃的组成及性能,并针对高硼硅平板玻璃澄清均化困难的问题进行了研究,比较了几、种澄清剂的澄清均化效果。