THE DETERMINATION OF IRON IN GLASS SAND1

Data are presented in tabular form showing the determination of iron in the Bureau of Standards Sample of Glass Sand, No. 81. The electrometric titration method, the H₂S reduction method, and the gravimetric method are described in detail.     

EFFECT OF IRON ON FLUORESCENCE IN GLASS*

The mechanism of fluorescence as it occurs in a uranium glass when irradiated with ultraviolet light is discussed with special reference to factors affecting both the intensity and spectral distribution of the fluorescence. The destructive effect of iron on the fluorescence of the glass is discussed and is illustrated by spectral absorption curves and by recorded fluorescence spectra. Conclusions based on these data indicate that iron not only absorbs a large portion of the exciting radiation, thereby decreasing the fluorescence emission, but also re-emits this absorbed radiation in the infrared, thus bringing about the infrared quenching of the fluorescence. Iron also causes an electrical disturbance around the fluorescing centers and is apparently capable of preventing the absorption of exciting radiation by these centers, further decreasing the intensity of fluorescence. A slight shift of the fluorescence spectrum toward shorter wave lengths is brought about by the presence of iron and is evidence of a weakening of the binding forces within the glass.     

STAINING OF GLASS CONTAINERS IN CONTACT WITH IRON*

A wet glass surface brought in contact with metallic iron acquires a brown stain which cannot be removed easily. This phenomenon was observed by the industry interested in the automatic washing of glass containers. Iron in contact with wet glass surfaces will produce a chemically detectable contamination in one minute and a visible stain in ten minutes. This reaction of the glass surface with iron is galvanic in nature. Iron immersed in water sends positively charged ferrous ions into solution and leaves the metal with a negative charge. In the neighborhood of the iron, a negative electrical potential is established in the glass surface which helps to attract the positively charged ions from the solution. The stain is a result of the interaction of the glass surface and the iron ions, thus leading through oxidation to the formation of an insoluble, colored ferric hydrosilicate. The staining can be prevented by reagents which (1) prohibit the corrosion of the iron, (2) block the active centers of the silica gel, and (3) produce anionic iron complexes.     

EFFECT OF IRON OXIDE ON MELTING OF GLASS*

The addition of small amounts of iron oxide (0.1 to 0.2%) to soda-lime-silica glass batches exerts a profound influence in increasing the output of glassmelting tanks as well as in favoring the production of higher quality glass. The color produced by this addition, moreover, is not objectionable for many uses of the ware. The accelerated melting rate probably is the result of a chemical effect of iron oxide in the batch and a physical property possessed by such glass to absorb radiation from the flames more efficiently. Attempts to measure these effects were made by rioting the melting rate of glasses which contain varying additions of iron oxide and by determining the temperature gradient that exists in glass when it is melted in a miniature tank. The presence of iron oxide aids melting and fining in crucible melts at 1200°C., but no effect was observed at higher temperatures. The measurement of temperature gradients in a pot holding 45 lb. of glass and heated by flames passing over the glass surface showed that the temperature gradient increases with iron oxide content.     

DETERMINATION OF COMPRESSIVE STRESS PRESENT IN PORCELAIN ENAMEL ON SHEET IRON*

A method for determining comparative compressive stress produced in porcelain enamel on sheet iron is described. The method consists of preparation of laboratory samples under carefully selected and controlled conditions and measurement of the warpage produced in the sample due to application of enamel on one side. Data obtained by the above method are compared with expansion curves. Several methods of analyzing the curves fail to produce correlation between expansion as determined on frit samples and compression in the porcelain enamel as indicated by the warp of sample plates. It is concluded that expansion curves on frit samples are not a satisfactory means of evaluating compressive stress in the porcelain enamel coating on sheet iron.     

EFFECT OF IRON OXIDE ON PROPERTIES OF SODA-DOLOMITE LIME-SILICA GLASS*

In two base glasses, the first containing 16% of sodium oxide, 10% of dolomite lime, and 74% of silica, and the second with 14% of sodium oxide, 12% of dolomite lime, and 74% of silica, iron oxide was systematically substituted for (a) Na₂O, (b) CaO·MgO, and (c) SiO₂ in amounts of 1, 3, and 5%. The effects of these substitutions on such properties as liquidus temperature, viscosity, deformation temperature, fiber softening point, density, coefficient of expansion, and the resistance of the glasses to dilute acid and distilled water, arc presented.     

STUDY OF PHOTOLUMINESCENCE IN GLASS*

The influence of composition and temperature on the fluorescence of glasses containing uranium and glasses containing cuprous oxide and stannous oxide was investigated. Secondary cations reduce the fluorescence of uranium in the glasses studied, depending to a certain extent on the electrostatic conditions they produce in the glass structure. The intensity of fluorescence as well as the structure of the spectrum diminishes in the order of phosphate, silicate, and borate glasses of equivalent compositions, which shows that fluorescence is favored by increase of oxygen in the glass structure without increasing the interfering secondary cations. Raising the temperature greatly diminishes the intensity of the fluorescence as well as the structure of the spectrum of glasses containing uranium. The fluorescence of the glasses containing cuprous oxide and stannous oxide as activators seems to be favored by increase in lime and increase in silica. These glasses possess appreciable phosphorescence, which appears to be enhanced by increase in silica and decrease in lime. A peculiar property of this type of luminescent glass is a maximum which it exhibits in its fluorescence-temperature relation-ship. There are indications that electrons are set free from the excited centers (copper atoms or small groups of copper atoms), which wander about in the glass structure.     

ANALYSIS OF SELENIUM IN GLASS*

A new method for the determination of selenium in glass is reported. It comprises fusion of the sample with sodium carbonate, dissolution of the melt in sulfuric acid, distillation of the selenium as selenium tetrabromide from a sulfuric-hydrobromic acid solution, and titration of the distilled selenium by the iodide-thiosulfate method. The method is rapid, accurate, and precise and recovers all forms of selenium. The recommended procedure is outlined.     

OXIDATION-REDUCTION EQUILIBRIA IN GLASS BETWEEN IRON AND SELENIUM IN SEVERAL FURNACE ATMOSPHERES*

This study has been limited to the reactions between iron and selenium in soda-lime and potash-soda-lime glasses melted in atmospheres of air, nitrogen, and carbon monoxide. Glasses containing selenium and iron, together and singly, were melted in the several atmospheres. and their spectral absorption curves between 350 and 1000 mμ were obtained. An analysis of these curves shows that under neutral or slightly oxidizing conditions selenites react with ferrous iron as follows: This reaction leads to an increase in red and brown and a decrease in blue colors. The decolorizing action of selenium may be explained by this reaction because the colorless selenite ion oxidizes the more colored ferrous ion to the less colored ferric ion, arid the increase in the red elemental selenium color physically compensates as a complimentary color for the remaining unoxidized ferrous ion. The results show that it is not necessary to postulate the formation of ferrous selenium to explain the color changes. The results also show that under reducing conditions the principal reaction is      

CAS系统微晶玻璃残余应力测定

分析了CAS系统微晶玻璃中热残余应力的形成机理,并对几种常见的残余应力的方法进行了比较,最后确定用普通X射线衍射法测定CAS系统微晶玻璃中的残余应力.     

THE RELEASE OF STRAIN IN GLASS*

Measurements of strain release¹ showed that check results were obtained only when the previous history of the samples was the same. Moreover, it was found that the release of strain was more rapid at first than could be accounted for by the equation of Adams and Williamson. This paper discusscs the effect of previous history on the measurements, describes an improved device for loading the specimens, and suggests a logarithmic equation which, in general, fits the observations better than that of Adams and Williamson. Tests of the equation are made both on data obtained from the modified apparatus described and on the data of Adams and Williamson. It is indicated that the Adams and Williamson equation gives too long an annealing time at higher temperatures and too short an annealing time at lower temperatures. It appears that the rate of release of strain depends on some power of the strain which varies from unity at high temperatures where the glass is a viscous fluid to a higher power at low temperatures where the release of strain is elastico-viscous in character. With a siugle specimen at any fixed temperature in the annealing range, however, it appears that the release of strain in various parts of the specimen takes place at a rate which is proportional to the strain, but that the rate undergoes continual change with time.     

DETERIORATION OF GLASS IN TROPICAL USE*

Glass deteriorates rapidly in tropical regions with a high relative humidity. Transparency decreases due to the growth of deposits of corrosion products, chemical decomposition of the surface layer to produce pits or holes, or contamination of the surface by organic material. The processes involved in tropical deterioration are similar to the chemical reactions of glass and water in other environments.     

THE FLOW OF GLASS IN TANKS*

The paper deals with the flow of glass in tank furnaces. Reference is given to previous work on this subject. Experimental data are given for water and other liquids and the physical principles are discussed. Illustrations indicate the direction of flow in a glass tank.     

PERMANENCE OF DISANNEALING STRESSES IN GLASS*

Nonmathematical considerations indicate that residual annealing stresses in glass are permanent although Ghering and Green do not draw this positive conclusion from their analysis of measurements over a seven-year period.     

EFFECT OF GLASS COLOR ON SETTING RATES IN MANUFACTURE OF GLASS BOTTLES *

It has been observed in the manufacture of bottles of the same size and shape from various colored glasses, such as emerald green and amber and the so-called flint bottle glass, that higher machine speeds are usually obtained in the case of the colored glasses. A laboratory test has been devised to measure the cooling rates of several colored and colorless glasses throughout their respective working ranges, which gives results paralleling the speeds obtained in actual bottle manufacture.     

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.     

ATOMIC CONSIDERATION OF IMMISCIBILITY IN GLASS SYSTEMS*

An attempt is made to apply the ideas of crystal chemistry to the problem of immiscibility in glass systems. Miscibility is favored by the tendency of the networkforming cations, Si, B, and P, to bond with all available oxygens in the melt. Immiscibility is favored in compositions which do not allow the other cations, such as Na⁺ and Ca⁺⁺, to be properly surrounded by unsaturated oxygens. The importance of this effect may be related to the valence and size of the cation. A qualitative discussion is given for a number of binary and ternary systems.     

EFFECT OF TIN IN GOLD RUBY GLASS*

The century-old use of tin compounds in the preparation of gold ruby, copper ruby, and silver yellow is based not on reduction phenomena but on its specific influence on the solubility of these metals in glass.     

DETERMINATION OF THE SOURCE AND MEANS OF PREVENTION OF STONES IN GLASS

The microscopic characteristics of different crystalline materials occurring as stones or lumps in glass are described and photomicrographs of stones originating from devitrification of the glass, incomplete solution of batch constituents, and incorporation in the glass of refractory wall material are reproduced. Methods of determining the location in the glass-making system of the source of stones, using microscopic as well as other methods, are given. Means of prevention or elimination of the stones are suggested.     

MICROSTRENGTH OF GLASS *

It is shown experimentally that if a minute area of a large piece of glass is tested for tensile strength, the stress supported is comparable with that of fine glass fibers and is some fifty or one hundred times the “strength” of the large piece tested in any of the ordinary ways. The experiment consists in pressing a small steel ball upon the glass surface, and so stressing, in tension, a minute annular zone around the circle of contact.