The liquidus te mperature of a glass is t he highest temperature at which equilibrium can coexist between the molten glass and the primary crystalline phase. An improved temperature-grad ient apparatus is d escribed for thc rapid d etermination of liquidus temperatures and rates of crystal growth in glasses. In this method the use of small glass fragmcnts confined in the cells of a platinum a ll oy holder largely eliminates the crror inherent in previous gradient method s. The proced ure is s imple and rapid. Liquidus tempe ratures in the range from 950° to 1,225°C were determined to a precision of 4 d eg rees C.Hates of crystal growth were found to be linear. The usefulness to the glass technologist of data obtained by this method is indicated.
Glasses in the System Barium Oxide-Boric Oxide-Silica 209havior of clear and opaque plates subjected to the same heattreatment.
V. SummaryA method has been developed for calculating temperature It distributions in glass plates undergoing heat-treatment.has been programmed for a high-speed digital computer and is ready for application to practical problems of glass technology. the differences, both qualitative and quantitative, in the be-
Acknow,edgmenhAcknowledgment is made to E. R. Michalik, formerly of Mellon Institute and now with the Pittsburgh Plate Glass Company, and to Carl Saalbach of the Westinghouse Electric Corporation for programming the high-speed digital computer.
Densities, refractive indices, liquidus temperatures, and primary phases of glass compositions in the glassforming region of the system BaO-BtOrSiOz were determined. Anomalous changesin properties were observed for a continuous change in composition. The possibility that there is a relation between the compounds indicated by the phase diagram and the actual units in the glass is suggested.
A series of Na20-8i02 glasses was studied for durability, hygroscopicity, glass electrode function, and apparent response to [Na+]. These glasses show three distinct regions of durability characteristics at pH 4.6: Below 81 percent of 8i02, where the glass is carried into solutioo; between 81 and 89.5 percent of 8i02, where differential solution of the constituents of the glass leaves a swollen silica-rich layer; a nd a region in which greatly reduced attack was indicated. Glass electrodes of low silica con te n t having poor chemical durability and high hygroscopicity exhibited large voltage departures approaching the values of a "pu nctured" mercury-filled electrode and a calomel half cell. The apparent response to [Na+] ran ged from 9 to 339 millivolts per pNa for the glasses of 82.6 and 56.6 percent. of i02, respectively.
These changes, which are brought about by variations in specific gravity and additions of electrolytes in the enamels studied, represent a wider range in set conditions than normally encountered in a laboratory or plant production work.Only those data pertaining to a typical commercial zirconia-opacified sheet-steel cover enamel have been presented since they embrace such a large span of consistencies. However, some exploratory studies have been made on other enamels such as a sheetsteel ground coat and a titania-opacified cover coat with highly satisfactory results. Sufficient data were obtained t o indicate the viscosimeter's successful application to these enamels.If handled with reasonable care and observing certain precautions, the Brookfield Svnchro-Lectric, or similar instrument, should afford the following advantages in measuring or controlling enamel slip consistency :(I) Rapid determinations.(2) Results translatable into absolute viscosity units.(3) Wide ranges.(4) (5) Portability.High accuracy and good reproducibility.
CHICAGO VITREOUS ENAMEL PRODUCT COMPANY RESEARCH LABORATORIES
CICBRO, ILLINOISABSTRACT Optical glasses with high indices of refraction and Abbe values are very desirable for wide angle lenses. In order to determine the range of compositions in which glasses of this type could be produced, oxides of lithium, beryllium, calcium, boron, lanthanum, or thorium were substituted for barium oxide or silica in a three-or-four component base lass. Substitutions were made on a mole-for-mole basis. The indices of refraction for glasses with indices of refraction ( n~) and Abbe values from 1.600 to 1.714 and 62.2 to 52.7, respectively, were made in small platinum crucibles.'i, t e C, D, F, and G' lines and the liquidus were determined for each glass. Experimental
Optical glasses with high ind ices of refraction and Abbe values are very desirable for wide-angle lenses. In ord er to determin e the range of composit ion s in which glasses of th is type eou ld be prod uced, oxides of Li , Be, Ca, B, La, or Th , were substit uted for BaO or Si02 in a th ree-0 1' fou r-compon e nt base gla ss . Su bstit ut ion s we re made on a mole-for-mole basis. The indices of refraction fol' tlle C, D, F , a nd G' lin es and t he liquidus we re determ ined for each g la s. Experimental glasses wit h indices of refra ct ion (n D) and Abbe values fl' om l.600 to l.71 4 and 62.2 to 52.7, respectively, " 'ere made in mall platinum cru cib les.
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