By heating alkali silicates under COt at high pressures, alkali carbonates are reformed t o an extent depending upon temperature, pressure, and chemical affinity. The CO? thus existing homogeneously dissolved in the glass, and other anions and oxygen similarly dissolved and in chemical equilibrium are termed "melt-residuals" (Schmelzrelikte).Their importance in planing, coloring, decolorizing. machine-working, vacuum bulb, and electric-lamp manufacture is discussed.

No abstract

Synthetic Mica Investigations, 1134 1 under compression a t room temperature. Again, the degree of compression developed is considered proportional to the difference in their respective coefficients of expansion. Thus, from thc coefficients of expansion of the enamels without mill 'iddition, as shown in column ( 5 ) , it may be assumed that the order of increasing strain would be D, B, A, and C. Although only enamels A and B are out of order, the coefficient of cxpansion of enamel C would not have predicted as great a \train as was actually produced, and that of enamel D would have predicted a greater strain than was produced.Column (6) lists the coefficients of expansion for all enamels :I\ detcrniincd by the use of formula (1 1).Since the magnitude of the strain produced between enamel aiid iron can be determined by the departure of the ringniovcmcut curve from the no-strain line a t any given temperature, the slope of this curve may be considered as a coefficient oC strain. Tlic coefficients of strain for the enamels tested are sliowii in column (7).Iicportcd with the cocfficient of strain for each enamel is its lower no-strain temperature. These two figures serve to aid i n the selection of an enamel for a specific purpose; for exaniplc, if clevatcd temperatures were to be encountered, an ciianicl with a lower no-strain temperature above that which would be encountered in service would be desirable. Other fxtors, such as the design of the piece to be enameled, should also be considered This ring test should also prove useful in studying the thcrmal history of high-temperature ceramic coatings, since this information would be valuable in determining the strain m d subsequent durability of the coating a t elevated temperatures. It also should provide a means of determining the thermal history of strains produced between glazes and ceramic bodies. VI. SummaryA modified ring test has been devised which serves as a means of determining the strain existing between enamel and iron from room temperature to the softening point of the enamel,(2) The strain data obtained by the ring test were in good agreement with those obtained by the warp test. This agreement existed for enamels with or without clay mill addition.(3) Clay added a t the mill had varying effects on the strain produced, depending on the reaction between the enamel and clay.(4) Changes in strain produced by the addition of clay were roughly proportional to the change in lower no-strain temperature produced by this addition.Coefficient of expansion data, as obtained from the interferometer, did not predict the strains which were actually produced. However, coefficients of expansion, calculated from formula (ll), were more of the order of magnitude required to produce the strains encountered in this investiga tion.(ti) The coefficient of expansion of the enamel run in the interferometer was evidently not the same as that of enamel on the iron. Such factors as mill addition, reaction of cover coat and ground coat, and heat-treatment were probably responsibl...

No abstract

A new ceramic composed entirely of synthetic fluorine mica manufactured by the hot-pressing technique is described. Its chemical, physical, and electrical properties are given. As the extensive isomorphism possible in the mica structure permits the variation and control of properties over a wide range, the characteristics of several different synthetic mica compositions are included. Hot-pressed mica is soft (2+ to 4+, Mohs' scale) and machinable, yet has a transverse strength of more than 8000 lb. per sq. in. As an electrical insulator, it compares with fused silica and ultra-low-loss steatite.With a rise in temperature, the dielectric constant remains essentially unchanged up to 300OC. ; some synthetic mica compositions show a n increase of less than 3% when they are heated to 4OO0C. The power factor of several synthetic mica compositions remains less than 2Oj, at 40Ooc., being 0.05% at room temperature.