Progress in Metallography

Abstract

THE application of micrographic analysis to the study of alloys has given to the metallurgist a new and important field of investigation, and every improvement in the established methods is worthy of attention. Some of the latest suggestions are made by M. Henri le Chatelier in the Bulletin de la Société d'Encouragement for September, last, the most noteworthy being in connection with the final stages of polishing. It is necessary for this work that the polishing powders should be perfectly classified according to the dimensions of the particles. The method of sorting by means of levigation, described by M. Osmond, is defective, owing to the fact, that the salts of lime in ordinary water cause coagulation and rapid deposition of minute particles suspended in water. Caustic lime and acids induce even more rapid settling, a fact that has proved of great commercial importance in the treatment of ore slimes by cyanide in South Africa.