92 



REPORTS ON INVESTIGATIONS AND PROJECTS. 



THE PUBLISHED WORK OF THE YEAR. 



The results of the laboratory work of the year just past are contained in 

 the following reviews of the papers published by members of the laboratory 

 staff: 



(i) Preliminary report on the ternary system CaO-AUOs-SiOz. A study of the consti- 

 tution of Portland cement clinker. E. S. Shepherd and G. A. Rankin. With 

 optical study by Fred. E. Wright. J. Ind. Eng. Chem., 3, i. 191 1. 



Two earlier papers from this Laboratory* having prepared the way for a 

 systematic study of the ternary systems, the present paper presents the 

 results thus far obtained with the interesting oxides, lime, silica, and 

 alumina. 



In the earlier work with mixtures of pure lime and silica, two compounds, 

 the metasilicate (CaO.SiO,) and the orthosilicate (2CaO.Si02), were defi- 

 nitely established, but no trace of the hitherto generally accepted tricalcic 

 silicate (3CaO.Si02) could be found in mixtures of pure lime and pure silica. 

 In the three-component system, on the other hand, the tricalcic silicate ap- 

 pears promptly with the addition of alumina to mixtures of appropriate lime- 

 silica concentration, and after a long and difficult experimental investigation, 

 involving the study of about 1,000 heat treatments of various compositions, 

 many of which required to be studied at temperatures between 1800° and 

 1900° C, it has finally been prepared pure, excepting for a small excess 

 (between i and 2 per cent) of orthosilicate or lime or both. 



Tricalcic silicate appears to be unstable at its melting temperature, and so 

 does not form from a melt of this composition. For the same reason, it does 

 not form eutectics with the adjacent compounds, calcium orthosilicate and 

 lime. Neither is there any evidence that the tricalcic silicate takes up calcium 

 orthosilicate or lime in solid solution. 



In addition to the tricalcic silicate, a new and probably unstable form of 

 the orthosilicate has been discovered which may prove to be of importance 

 in Portland cement. 



The general boundaries of the different phases occurring throughout the 

 entire diagram (for diagram cf. original paper) of the ternary system CaO- 

 AlaOg-SiOo, have been established, together with the course of the boundary 

 curves. From these it is possible to predict the compounds which will crys- 

 tallize out of a lime-silica-alumina cement of any composition, provided only 

 that the compounds are intimately mixed and the heat is sufficient to bring 

 the mixture to equilibrium during formation. The exact location of the quin- 

 tuple points, with the exception of points 13 to 17 and the isotherms, remains 

 to be established. The location of these quintuple points is as follows : 



*_"The lime-silica_ series of minerals." Arthur L. Day, E. S. Shepherd, and F. E. 

 Wright. Am. J. Sci. (4), 22, 265 (1906). "The binary systems of alumina with silica, 

 lime, and magnesia." E. S. Shepherd, G. A. Rankin, and F. E. Wright. Am. J. Sci. (4), 

 28, 293 (1909). 



