162 



CEMENTS, LIMES, AND PLASTERS. 



TABLE 67. 

 EXPANSION OP MAGNESITE BRICKS ON HEATING. (LE CHATELIER.) 



References on magnesite bricks. The following papers contain data 

 regarding the manufacture and properties of magnesia bricks. 



Bischof, C. On magnesia bricks. Proc. Inst. Civil Engineers, vol. 112, 



pp. 381-383. 1893. 



Egleston, T. Basic refractory materials. Trans. Amer. Inst. Mining En- 

 gineers, vol. 4, pp. 455-492. 1876. 

 Pennock, J. D. Laboratory note on the heat-conductivity, expansion, and 



fusibility of firebrick. Trans. Amer. Inst. Mining Engineers, vol. 26, 



pp. 263-269. 

 Percy, J. Magnesia crucibles and bricks. Metallurgy, vol. 1, pp. 134-137. 



1875. 

 Ylasto, S. Jo The magnesite industry. Engineering and Mining Journal, 



March 10, 1900. 



Weiss, N. Magnesite in Hungary. Iron Age, Jan. 15, 1903, pp. 20-21. 

 Anon. Magnesite [and magnesia brick]. Mineral Industry, vol. 10, pp. 438- 



439. 1902. 



Oxychloride Cements. 



In 1853 the chemist Sorel discovered that zinc chloride, when mixed 

 with zinc oxide, united with it to form a very hard cement. Later it 

 was discovered that the same held true of a mixture of magnesium 

 chloride and magnesia. The product in both cases is the same an 

 oxychloride of zinc or magnesium respectively. Chlorides and oxides 

 of several other elements possess this same property, but it has been 

 utilized commercially only in the cases of the zinc and magnesium com- 

 pounds. Of these, zinc oxychloride is extensively used as a stopping 

 by dentists. Magnesium oxychloride, called commonly Sorel cement 

 or magnesia cement, has more important technical uses. 



Sorel 's magnesia cement is made by mixing calcined magnesia with 

 a solution of magnesium chloride of 25 or 30 Baume. If the magnesia 

 has been prepared from magnesite, it usually contains a little residual 

 carbon dioxide (C0 2 ), and though setting very rapidly and giving a 

 very strong cement, cracks are apt to develop during setting. When 



