. Metallographic etching reagents: I, for copper. eposit upon the specimen formed by silver nitrate was re-moved by a swab of cotton and that formed by bromine waterby an immersion in ammonium hydroxide. In all cases it isvery essential that the two solutions be thoroughly mixed, other-wise some queer misleading results may be obtained, caused bythe diffusion currents within the liquid. This is particularly trueif the sulphuric acid is added in the concentrated form in makingup the acid solutions. In Fig. 15 the use of electrol3rtic etching for copper is proper regulation of the
. Metallographic etching reagents: I, for copper. eposit upon the specimen formed by silver nitrate was re-moved by a swab of cotton and that formed by bromine waterby an immersion in ammonium hydroxide. In all cases it isvery essential that the two solutions be thoroughly mixed, other-wise some queer misleading results may be obtained, caused bythe diffusion currents within the liquid. This is particularly trueif the sulphuric acid is added in the concentrated form in makingup the acid solutions. In Fig. 15 the use of electrol3rtic etching for copper is proper regulation of the conditions an etching showing verybrilliant contrast may be obtained. An examination of Figs. lo to 14, inclusive, each of which illus-trates the behavior of one of the different forms of copper usedwith the same series of etching reagents, shows that, in general,the various forms of copper are affected very similarly by anyparticular etching solution; for example, silver-nitrate solution 66o Scientific Papers of the Bureau of Standards [VoL i6. Fig. io.—Results obtained by etching cast copper with the reagents listed in Table i. Original magnification, Xioo, reduced to yj The number under each micrograph refers to the etching reagent used R^onj Metallographic Etching Reagents for Copper 661
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Keywords: ., bookcentury1900, bookdecade1920, bookidmetallograph, bookyear1920
