VOLCANIC FUEL. 405 



the attempt to use it for this jjurpose. In 1887 Le Chatelier ^'^ pro- 

 posed the formula x [(3CaO)SiO,] + y [(3CaO) Al^Oj] for Portland 

 cement, but S. B. and W. B. Newberry ^^ have shown that the formula 

 X [(SCaOjSiO,] + y [(3CaO) AljOg] produces a much better cement. 

 Both of these formulsE are based on a more or less ideal condition of 

 fluxing and there are cases where even the latter gives a percentage of 

 lime in the finished product very much higher than that of the average 

 Portland cement ; however, it is valuable to the cement chemists as a 

 limiting formula. Bleininger ^^ has made a series of investigations 

 from the results of which he concludes that "for the dry ground mix- 

 tures the formula (2.8CaO)SiO,,(2CaO)Al203 is the safest." Several 

 cement batches were made up with the sample of tuff from Manila 

 according to the formula for Portland cement, calculated in such a 

 way that after burning the percentage of lime would vary within the 

 limits of good Portland cement. The materials were combined so that 

 the finished product contained : 



For each molecule 



of SiOa, molecules of 



CaO resp. MgO, as 



follows : 



And tor each mole- 

 cule of AI0O3 resp. 

 FeoOs, molecules of 

 CaO resp. MgO, as 

 follows : 



2.8 





2 



2.6 





2 



2.4 





2 



2.2 





2 



I have not as yet been able to obtain a furnace temperature above 

 1,350° C and that is too low satisfactorily to burn a cement. All of 

 the above mixtures when burned at this temperature disintegrated spon- 

 taneously on cooling, which is characteristic of the dicalcium silicate 

 (2CaO)SiO,^'' and indicates that the heat was not sufficient to fuse the 

 other compounds of silica, alumina, lime and iron oxide which promote 

 the union of silica and lime to form the tricalcium silicate (3CaO)Si02, 

 which is the basis of hydraulic activity in Portland cement. In a small 

 crucible over a blast lamp I prepared a cement from the ingredients 

 limestone, clay, and shale which set well, but a sufficient quantity could 

 not be obtained in this way to ascertain the physical constants. With 

 this same method I could not produce a cement from the tuff cement 

 batch, indicating that if cement can be produced from this material 

 a still higher temperature is necessary. 



Recentlj' Howe ^' has shown that a cement of good quality can be 

 produced from Panama rhyolite tuff, which is not very unlike that of 

 the Philippine Islands in composition. The Panama materials used were 



"Ann. des Mines (1887), 11, 345. 

 "/. Soc. Chem. Ind. (1897), 16, 887. 



'"Bleininger, A. V., The Manufacture of Hydraulic Cements, Geol. Sur. of Ohio 

 (1904) (4), 3, 236. 

 " Le Chatelier, loc. cit. 

 "Boon. Geol. (1907), 2, 655. 



