Of alkali metal silicate

Another characteristic feature of the silicate melts is the formation of two immiscible liquids in the region of high concentration of Si02. Such a behavior is observed, for example, in the systems of alkali metal silicates and earth alkali metal silicates. 

Formation of alkali metal silicates (ca. 1,020 K) (the major component is plagioclase feldspar). 

Figures 1, 2, and 3 show Si NMR spectra of alkali metal silicate solutions with silicate ratios (R = [SiC>2]/[M20]) of R - 0.4, 1.5, and 2.0, respectively. The total Si02 concentration is 1.75 molX...

Several metal silicates have been prepared in true SCH2O above 400 "C, mostly for electronic purposes. Thus, Laudise and co-workers prepared an extensive series of alkali metal silicates of the rare earths [93] ... 

The term percent weight as applied to aqueous solutions of alkali metal silicates refers to the percent by weight of silicate, measured as Si02, in the total solution. 

The higher the ratio of concentrated aqueous solutions of alkali metal silicates the higher the colloidal silica content, but for each ratio the colloidal silica content decreases with dilution of the solution. 

The compositions of the invention contain 3-15 parts, per 100 parts of sand binder mixture by weight, of a binder system comprising a water soluble alkali metal silicate, amorphous colloidal silica and water. The key is to have very finely divided amorphous silica particles of colloidal size dispersed within the alkali metal silicate bond. It is inherent in the nature of water soluble alkali metal silicates having a molar ratio Si02/alkali metal oxide (M2O) above about 2.5, that colloidal silica is present. In the case of silicates having a ratio higher than 3.5, the colloidal silica content is such that they may be employed without adding more colloidal silica, but in the case of alkali metal silicates of lower sUica/alkali metal oxide ratio there is little or no amorphous colloidal silica present so that amorphous colloidal silica must be added in order to produce the cores and molds of the present invention. 

Uchino, T., Sakka, T., Ogata, Y., and Iwasaki, M. (1992) Changes in the Stmcture of Alkali-Metal Silicate Glasses with the type of Network Modifer Cation An ab initio Molecular Orbital Study, J. Phys. Chem., 96,2455-2463. 

A simple potentiometric method for the determination of silica in solutions of alkali metal silicates is described. The precision of the determination of Na20 and SiQz in silicates was improved and the determination time decreased by developing a potentiometric titration method. Better determination results due to potentiometric detection of the endpoint pH are demonstrated by comparison with gravimetric determination of Na20 and Si02 in water glass containing 26-260 g/L. The potentiometric determination method can be easily automated. 

Tretinnik, V.Yu., Terlikovskii, E.V., and Skorobogach, L.P., Content potentiometric determination of silica in solutions of alkali metal silicates. Glass and Ceramics (1993), (7), 27-29 (in Russian). 

Oxide iorts in molten nitrates exist as the so-called pyronitrate ions N20 which are strong bases with the basicity approximately eqttal to those of COj. " The modem rmderstanding excludes the existence of nitrogen compoimds with the coordination mrm-ber exceeding 3 by oxygen, hence pyronitrate hardly exists in the mentioned conditions. Indeed, other oxoanion studies, demorrstrated the absence of the mentioned ion in basic nitrate solutiorrs. A possible way for the stabilization of in nitrate melts is the formation of alkali metal silicates due to reactiorts with walls of a crucible (usirally it is pyrex). 

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