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.     

METALLURGICAL STUDY OF CAST IRON FOR GLASS MOLDS*

Research data are reported on the susceptibility of cast iron to cracking when it is used in molds for processing glassware. An accelerated test was run to produce cracking in a shorter time than would occur in the production of glassware. The results from this test indicate that sand-cast iron is more resistant to cracking than chill-cast iron of the same composition. The alloyed chill-cast irons, however, cracked less severely than the unalloyed iron. An annealing heat-treatment of these irons increased resistance to cracking, whereas a spheroidizing heat-treatment reduced resistance. A maximum resistance to cracking together with the ability of the iron to take a high polish apparently may be obtained by using an annealed, chill-cast alloy iron containing chromium, nickel, and molybdenum. Such iron is more susceptible to cracking than a sand-cast iron of the same composition, but the latter type is incapable of a sufficiently high polish and usually has an open, porous structure.     

EFFECT OF COMPOSITION AND TEMPERATURE ON SOLUBILITY OF IRON OXIDE IN GROUND-COAT ENAMEL GLASS*

The solubility of iron oxide in ground-coat enamel glasses at various temperatures was studied by adding varying amounts of ferric oxide to the milled enamel and giving the mixture a heat-treatment to acquire uniformity without devitrification at the desired temperature. The iron oxide solubility was obtained by finding the breaking point in the curve for iron oxide versus index of refraction. The frit solubilities were obtained at 1400°, 1600°, 1800°, and 2000°F. with variations in Na₂O, B₂O₃, A1₂O₃, CaF₂, CaO, F₂, SiO₂, COO, NiO, MnO₂, BaO, and MoO₃. Data are given on a number of commercial frits.     

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.     

双光束火焰法(AAS)测定玻璃中Li含量

对采用原子吸收法测定玻璃中的锂含量进行了分析、讨论,并给出了该方法锂测定的线性范围、精密度等.     

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      

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.     

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.     

STUDY OF DIFFUSION IN GLASS*

An introductory study was made of diffusion into glass from salts, with silver nitrate as the chief source of diffusing particles. The optimum test conditions were a temperature of 900°C. and a test time of 108 hours. The results noted were (1) effect of time, (2) effect of temperature on the distance of diffusion, (3) variation of silver concentrations in the glass with the distance of diffusion, and (4) a check of Fick's law of diffusion. The concentration gradient of silver from a diffusing interface was determined with the use of a spectrograph and corresponding particle sizes with an ultramicroscope. In addition to the silver nitrate, a number of other salts were tested at several temperatures. The development of Liesegang rings was noted in some of the samples. The nature of diffusion in glass was deduced from the results.     

IRON OXIDE IN ENAMEL GLASS AS DISSOLVED FROM THE METAL BASE*

The iron oxide content of an enamel glass was measured by the use of a predetermined curve representing iron oxide versus the index of refraction. It was found that the iron oxide content of the glass adjoining the interface between the enamel and the iron base rises sharply in the early stages of firing to a value close to the solubility limit of the glass after which it gradually falls to a constant value. The iron content at the surface remains low until that at the interface decreases, whereupon the surface concentration correspondingly increases. The cobalt additions resulted in a lower iron content in solution at the interface, but they increased the dendrite content of the glass. A decrease in the cobalt content resulted in an opposite effect. There was a direct relation between the amounts of cobalt and dendrites and the adherence. The effects of temperature and thickness of application are given, and the results are discussed.     

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.     

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.     

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.     

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.