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Volume 2, page 39, 1917 HOW TO ETCH METEORITES THE EDITORS THE surface to be investigated is first ground flat and smooth; the larger the surface the greater will be the opportunity afforded to study the details of its structure. The Foote Mineral Company's method of etching is as follows:1 1. Wash the specimen with benzine. 2. Lacquer the unpolished back and edges with a lacquer known as "steel gloss" diluting to about one-half with benzine. When this side is dry, carefully remove with benzine any lacquer which may have run over the edges onto the polished surface. An electric fan hastens the drying of the lacquer. 3. Lacquer any nodules. They should be completely covered, as they are readily attacked by the acid, and will stain the etched surface. 4. Place the iron so that the polished surface is horizontal. Wash with 5 to 15 per cent solution of C. P. nitric acid for from 15 seconds to 4 or 5 minutes, until the etching is brilliant. If etched much longer, the iron will darken. When the surface begins to get rough, the maximum brilliancy has been reached. The acid should be kept as thick and as even as possible by rubbing the plate with a large brush. As the acid becomes discolored, it should be brushed off and clean acid added. 5. To clean and facilitate rapid drying, quickly put the section into clean warm water (120° to 130° F.) for several minutes, rubbing with a brush. 6. Dry in a few seconds with blotting paper. 7. Thickly lacquer the etched surface at once. To avoid oxidizing, the operations from 4 to 7 should be accomplished as quickly as is practicable, by having all the materials at hand. NOTE 1 From "Meteorites, Their Structure, Composition, and Terrestrial Relations" Oliver C. Farrington; Chicago, 1915. [var:'startyear'='1917'] [Include:'footer.htm'] |