. Transactions. enon observed in the hardening of cement. A mixtureoriginally consisting of isolated grains, when tempered with water, isprogressively transformed by chemical reaction into a coherent mass. H. LE CHATELIER AND B. BOGITCH 143 In the same manner, the isolated grains of quartz in a brick become set oncontact with melted silicates, which operate as solvent. Quartz is unstable at temperatures above 800°, but owing to its re-markable passive resistance, it is able to remain for a long time in thatcondition at very high temperatures, even up to 1600°. If it is then broughtinto contact
. Transactions. enon observed in the hardening of cement. A mixtureoriginally consisting of isolated grains, when tempered with water, isprogressively transformed by chemical reaction into a coherent mass. H. LE CHATELIER AND B. BOGITCH 143 In the same manner, the isolated grains of quartz in a brick become set oncontact with melted silicates, which operate as solvent. Quartz is unstable at temperatures above 800°, but owing to its re-markable passive resistance, it is able to remain for a long time in thatcondition at very high temperatures, even up to 1600°. If it is then broughtinto contact with a solvent, melted silicates for example, it dissolvesin that with a readiness very much greater than that of the more stableforms of sihca, cristobalite and tridymite. This is due to the unanswer-able and thoroughly established laws of physical chemistry. The quartzthus gives rise to supersaturated solution, from which one of the morestable varieties soon begins to crystallize. The melted mass, now being. Fig. 7. Fig. 8. Fig. 7.—Well fired American brick, with nettvork of tridymite betweenthe quartz grains, which are almost completely transformed into cris-TOBALITE. Polarized light; magnification, X 136. Fig. S.—AssAiLLY brick, remaint;ng for a year in one of the flues of aMartin furnace. Complete transformation into coarse-grained tridy-mite, with characteristic inclusions. Polarized light; magnification,X 136. no longer saturated with respect to quartz, is able to dissolve additionalquantities of it. Gradually, therefore, the entire amount of quartzrecrystaUizes into the variety that is most stable at high temperatures,tridymite. In practice, if the firing of sihca brick has not been sufficientlylong, the proportion of cristobalite, and sometimes even of quartz, isgreater than that of tridymite in the finished product, if of poor for almost a month at the highest temperature of the steel fur-nace is necessary to transform silica completely into tridy
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
