. Transactions. rature during heating. Abrupt heatingmay produce expansion three to six times as great as a slow heating, suchas is maintained in well conducted kilns. When the change from quartz to tridymite occurs in a massive un-fractured block, it causes a linear expansion of about per cent. How-ever, by a sufficiently slow firing, the apparent expansion can be reducedto 2 per cent., that is to say, a value below that of absolute is accompanied by a parallel diminution in the volume of the other hand, if the heating during the first firing is too abrupt, andstil
. Transactions. rature during heating. Abrupt heatingmay produce expansion three to six times as great as a slow heating, suchas is maintained in well conducted kilns. When the change from quartz to tridymite occurs in a massive un-fractured block, it causes a linear expansion of about per cent. How-ever, by a sufficiently slow firing, the apparent expansion can be reducedto 2 per cent., that is to say, a value below that of absolute is accompanied by a parallel diminution in the volume of the other hand, if the heating during the first firing is too abrupt, andstill more if, after an insufficient firing, the transformation is concluded H. LE CHATELIER AND B. BOGITCH 149 only in the steel furnace, the linear expansion may reach 10 per cent.;there would then be a considerable increase of porosity, rather than areduction. The brick would become both less strong physically and alsomore permeable to slag, to say nothing of the ruptures produced directlyby the expansion. +10 «. 2000 -105 Plate II.—Expansion op silica brick under varying conditions. In the accompanying diagram (Plate II), the solid line represents thetheoretical linear expansion of a compact mass. The dotted line showsthe normal expansion of a well fired brick not introduced into the steelfurnace until after the transformation of the quartz; in this case, oneshould expect a minimum expansion of 2 per cent, in the kiln, and of 1per cent, in the steel furnace. The broken lines represent the expansionof a badly fired brick inserted prematurely and abruptly into a steelfurnace. Transformation of Quartz The expansion of brick, which is intimately related to the transfor-mations of quartz, is of the greatest importance from the point of viewof the manufacture of silica lirick, and of their use in steel experiments on this subject have not offered so complete a solutionof the problem as we could have desired. 150 MANUFACTURE OF SILICA BRICK « Days experiments^ have sh
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
