Metallography of the Precious Metals**Editor's Note: Of all the inquires that are sent to the Editorial Offices of METALLOGRAPHY, among the most frequent and popular are those that deal with the inert or precious metals and their alloys. The inertness of such alloy systems presents a real challenge to the metallographer, and this fact is known all-too-well by this particular Editor, who has two platinum phase diagrams to his credit in the open literature. Because of this high degree of interest in such specialized and difficult metallographic techniques, this detailed technological presentation by two members of the Engineering Staff at Engelhard is given now as an invited paper.

Special metallographic procedures are presented which produce flawless photomicrographs of the precious metals and their alloys. In addition to conventional metallographic techniques, special commercial and automated apparatus are described which greatly facilitate the metallography of metals such as ruthenium and osmium. Finally, a series of photomicrographs of alloys rich in the six platinum group metals, silver, and gold is presented demonstrating the techniques described as a comparative guide for the metallographer.