Alkali-lead-silicates

Cu-sheathed wire 8095 Alkali-lead silicate, high electrical insula- Lead glass, stem glass for electric lamps... 

Then and Pantano used XPS to characterize changes in the surface of an alkali lead silicate glass on reduction with hydrogen at 5(X)°C. The reduction in the intensity of the non-bridging oxygen O Is peak was correlated with the formation of metallic lead which could evaporate from the surface leaving a silica rich layer (Then and Pantano, 1990). 

Lead silicate glasses having different mole ratios of Si02 to PbO and containing different amounts of alkali/alkaline earth metal oxides were prepared by conventional melt-quench method. The different structural units of Si present in these glasses were identified by Si MAS NMR. ... 

Copper Enamel. A vitreous enamel specifically compounded for application to copper, the composition is essentially lead silicate with small additions of alkalis, arsenic oxide and (sometimes) tin oxide. 

Sulphates, silicates, carbonates, colloids and certain organic compounds act as inhibitors if evenly distributed, and sodium silicate has been used as such in certain media. Nitrates tend to promote corrosion, especially in acid soil waters, due to cathodic de-polarisation and to the formation of soluble nitrates. Alkaline soils can cause serious corrosion with the formation of alkali plumbites which decompose to give (red) lead monoxide. Organic acids and carbon dioxide from rotting vegetable matter or manure also have a strong corrosive action. This is probably the explanation of phenol corrosion , which is not caused by phenol, but thought to be caused by decomposition of jute or hessian in applied protective layers. ... 

The behaviour of iridium is closely analogous to that of rhodium its corrosion diagram is very similar and it is, with rhodium, one of the least corrodible of metals. It is unattacked by alkalis, acids or oxidising agents in aqueous solution, although a fused mixture of caustic potash and potassium nitrate will attack it. The metal has an excellent resistance to fused lead oxide, silicates, molten copper and iron at temperatures up to 1 500°C. Additions of iridium to platinum considerably raise the corrosion resistance of the latter to a very wide range of reagents. 

Solutions of monosilicic acid may also be obtained by careful hydrolysis of tetrahalo-, tetraalkoxy-, or tetraacyloxysilanes by electrolysis or acidification of alkali silicate solutions or by ion exchange (qv). By operating under carefully controlled conditions at low temperature and pH, solutions may be obtained that remain supersaturated with respect to amorphous silica for hours at temperatures near 0°C. Eventually, however, polymerization reactions involving the formation of siloxane linkages occur, leading ultimately to the formation of colloidal particles and further aggregation or gel... 

These associations are noted by Hay (1966) as being found in sequences of sedimentary rocks or altered pyroclastics buried to depths greater than 3,000 meters and generally less than 10,000 meters. However, the limits are actually vague and the identifications imprecise. The relatively frequent occurrence and persistence of albite or potassium feldspar and alkali zeolite in such rocks leads one to believe that they can coexist stably in nature. This could be, however, a misleading conclusion based upon too few observations. The elimination of the silicic, alkali zeolites and the persistence of montmorillonite is known to exist in series of deeply buried rocks (Ii-jima, 1970 Moiola, 1970 Iijima and Hay, 1968). 

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