The original compilation of phase diagrams was made by F. P. Hall and Herbert Insley and was published as the October, 1933, issue ofThe Journal of The American Ceramzc Soctety. These authors then followed with a supplement, published as the April, 1938, issue of the sameJournal, and with another complete compilation which was published as Part I1 of the Sovember, 1947, issue of thisJournal.The following compilation is the first supplement to the Sovember, 1947, issue. It includes corrections of errorst and omitted diagrams as well as those published since the 1917 compilation was printed.It is to be understood that temperatures are given in degrees centigrade and the compositions are given in weight percentage unless otherwise stated on the individual diagram.