2 Rankin and ^Wright — Ternary System CaO-Al 2 O s -Si0. 2 . 



thus discovered upon a number of geological inquiries and 

 upon the problem of the nature of portland cement clinker. 

 Many papers on this general topic have, of course, already 

 been published, but the work recorded is, in the main, frag- 

 mentary and of little avail in settling the large general ques- 

 tions involved. The present investigation aims to treat the 

 system rather completely, to ascertain the equilibrium relations 

 in the system. To this end we have determined all the possible 

 compounds which are found in dry melts of the three oxides CaO, 

 Al a 3 , Si0 2 , studying especially those which are stable at the 

 liquidus; this involves measurements of the respective melting 

 points or dissociation temperatures, and the determination of the 

 invariant points, boundary curves (monovariant systems) and 

 fields of stability (divariant systems) of the various compounds. 



In the following pages we present a summary record of the 

 work performed ; it is the first thoroughgoing attempt, we 

 believe, to determine all the compounds, both binary and ter- 

 nary, made up only of CaO, A1 2 3 , Si0 2 , and the mutual 

 relations of these compounds, many of which have, of course, 

 previously been made synthetically by others. The data 

 obtained are made use of in a discussion of the nature and 

 constitution of portland cement clinker and of the formation 

 of certain natural minerals from the magma. 



Three papers dealing with this system have already been 

 published from this laboratory. The first two dealt with the 

 binary systems,* while in the thirdf provisional locations were 

 assigned to ternary quintuple points and boundary curves and 

 the relations discovered applied in a discussion of the constitu- 

 tion of portland cement clinker. In the present paper we are 

 able to give more exactly the location of eutectics, quintuple 

 points and boundary curves, together with the corresponding 

 temperatures. Owing to the large number of data it will not 

 be possible to give in a paper of this nature more than the 

 mean values obtained from a large number of determinations 

 of the various points. 



THE COMPONENTS AND THE BINARY SYSTEMS. 



It is well to begin by reviewing briefly the results obtained 

 in the study of binary systems, partly in order that we may 



*The Lime Silica Series of Minerals. A. L. Day, E. S. Shepherd, F. E. 

 Wright, this Journal (4), xxii, 265, 1906. The Binary Systems of Alumina, 

 with Silica, Lime and Magnesia, E. S. Shepherd, G. A. Eankin, F. E. Wright, 

 ibid. (4), xxviii, 293, 1909. 



f Preliminary Report on the Ternary System CaO-Al 2 3 -Si0 2 . A Study 

 of the Constitution of Portland Cement Clinker. E. S. Shepherd, G. A. 

 Eankin, F. E. Wright, J. Ind. Eng. Chem., iii, 211-227, 1911. 



