Sodium silicate melt

Manganese in sodium silicate melts. Geochim. Cosmochim. Acta, 44,887-93. 

Figure 33. Pressure dependence of oxygen diffusion rates in silicate melts, modified after Tinker and Lesher (2001). Data for the sodium-silicate melts are taken from Poe et al. (1997), dacite from Tinker and Lesher (2001), basalt from Lesher et al. (1996) and diopside from Reid et al. (2001). Inset shows results from computer simulations (Angell et al. 1982 — NaAlSi20e, solid Nevins and Spera 1998 — CaAl2Si20s, open) at mnch higher temperatnres of 4000 to 5000°C which show qnalitatively similar behavior. Note how the maxima in pressure dependence shifts to lower pressures for more polymerized, Al-bearing melts whereas in diopside there is actually a minima in the data set see text for details.

Critical temperatures often follow a simple trend for systems of related compositions. The critical temperature of alkali silicate melts, for example, decreases in the order of increasing radius of the alkali ion present, such that lithium and sodium silicate melts clearly exhibit metastable immiscibility, while the existence of immiscibility in potassium silicate glasses has not been conclusively established. There is no evidence for the existence of phase separation in the rubidium or cesium silicate systems. 

Silicon. Ionization of Cl from [0(CMe = NNMe2)2SiClPh] has been observed using Si NMR spectroscopy. Si NMR spectroscopy has been used to study the formation of [(MeO)Si(OH)3] in methanolic alkaline silicate solutions. The role of Na+ in the interaction mechanism of sodium silicate melt has been probed by and Na NMR spectroscopy. Si NMR spectroscopy has provided evidence of pentaoxosilicon complexes in dilute neutral aqueous silicate solutions. ... 

M. Leister, D. Ehrt, G. von der Gonna, C. Russel, F.W. Breitbarth, Redox states and coordination of vanadium in sodium silicates melted at high temperatures. Soc. Glass Technol G. Tricot, L. Montagne, L. Delevoye, G. Palavit, V. Kostoj, Redox and structure of sodium-vanadophosphate glasses. J. Non-Cryst. Solids 345-346, 56-60 (2004)... 

Figure 8. Probability distribution P n) of the ring length for Si02 and various sodium silicate melts at r = 3(XK) K. From Winkler et al. [56]. 

Blundy JD, Falloon TJ, Wood BJ, Dalton JA (1995) Sodium partitioning between clinopyroxene and silicate melts. J GeophysRes 100 15501-15515... 

Patented proposals have been made to heat sodium chloride with phosphoric acid (A. Delhaye) zinc or lead pyrophosphate (L. J. F. Margueritte) or ferric phosphate (A. R. Arrott). The resulting soluble sodium phosphate is decomposed by boiling with lime to form sodium hydroxide, which, if needed, can be converted into carbonate by a current of carbon dioxide. These methods are quite impracticable. In 1809, J. L. Gay Lussac and L. J. Thenard proposed to make soda by the action of steam on a mixture of sodium chloride and silica If these two compounds are melted together there is very little action, for the salt volatilizes before anything but a superficial combination takes place, and the action of salt in the glazing of pottery is probably made possible by the aq. vapour in the furnace gases. The sodium silicate formed by the joint action of sodium and... 

Silicon carbide is comparatively stable. The only violent reaction occurs when SiC is heated with a mixture of potassium dichromate and lead chromate. Chemical reactions do, however, take place between silicon carbide and a variety of compounds at relatively high temperatures. Sodium silicate attacks SiC above 1300°C, and SiC reacts with calcium and magnesium oxides above 1000°C and with copper oxide at 800°C to form the metal silicide. Silicon carbide decomposes in fused alkalies such as potassium chromate or sodium chromate and in fused borax or cryolite, and reacts with carbon dioxide, hydrogen, air, and steam. Silicon carbide, resistant to chlorine below 700°C, reacts to form carbon and silicon tetrachloride at high temperature. SiC dissociates in molten iron and the silicon reacts with oxides present in the melt, a reaction of use in the metallurgy of iron and steel (qv). The dense, self-bonded type of SiC has good resistance to aluminum up to about 800°C, to bismuth and zinc at 600°C, and to tin up to 400°C a new silicon nitride-bonded type exhibits improved resistance to cryolite. 

Fox, K. E., Furukawa, T. White, W. B. (1982) Transition metal ions in silicate melts. Part 2 Iron in sodium silicate glasses. Phys. Chem. Glasses, 23,169-78. 

The very high temperatures required to melt quartz were not attainable by early craftspersons. Hence, they prepared sodium silicate glass by mixing together and... 

The product is called water glass, because when solid, it actually is a glass but unlike lime-soda glass (ordinary window glass), it is soluble in water. The process is carried out in large tank furnaces similar to window glass furnaces. The materials are introduced in at intervals, but the products may be drawn off continuously if desired. A mixture of salt cake and coal may replace a portion of the soda ash. As the melt leaves the furnace, a stream of cold water shatters it into fragments. These are dissolved with superheated steam in tall, narrow steel cylinders with false bottoms,14 and the product liquor is clarified.15 Sodium silicates are sold as solutions that vary from the most viscous, 69°Be, to the thinner solu-... 

Although there is no general model for activity-composition relationships in silicate melts, several studies have shown that, under certain circumstances, a semi-empirical approach works reasonably well. Blundy et al. (1995) investigated the partitioning behavior of sodium between clinopyroxene and silicate melts over wide ranges of pressure and temperature. They showed that the crystal-liquid partition coefficient Dfja bears a very simple relationship to the equilibrium constant Xj,ja for the melting reaction ... 

---