ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 333 



Oxygen in Metals and Alloys.* — E. F. Law discusses this subject, 

 and gives photomicrographs of copper and of bronze to show the mode 

 of occurrence of oxides. As a rule, metallic oxides are insoluble in 

 solid metals and alloys, and are found as particles embedded in the 

 metal. The addition of arsenic to copper containing oxygen prevents 

 the formation of the characteristic eutectic structure of copper and 

 cuprous oxide. The oxide occurs in the massive form. 



Structure of Electrolytic Copper. t — The microscopic structure of 

 electrolytically deposited copper, and the effect of variation of current 

 density and of concentration of solution have been studied by 0. Faust. 

 The crystallites are usually parallel with the direction of the current. 

 Like worked copper, electrolytic copper develops twinned crystals on 

 annealing ; this, with other evidence, points to the existence of stress in 

 electrolytic copper. 



Formation of Twin Crystals by Quenching". J — By examination 

 with oblique illumination, with different directions of incidence of the 

 light, C. A. Edwards has shown that the characteristic dark and light 

 acicular structure of quenched aluminium-copper alloys containing 

 9-16 p.c. aluminium is due to prohfic twinning of a homogeneous 

 super-cooled soHd solution. In each crystal grain the number of sur- 

 faces on which twinning has occurred is very great. The almost 

 identical structure of quenched carbon steels may be due to the same 

 phenomenon of twinning. It is suggested that the hardness associated 

 with the acicular structure in quenched alloys may be due to the forma- 

 tion of large quantities of Beilby's amorphous phase by the mechanical 

 distortion of the solid solutions in twinning and slipping. 



Intercrystalline Cohesion in Metals.§ — W. Rosenhain and D. 

 Ewen put forward the hypothesis that in pure metals the crystals are 

 enveloped in an amorphous cement, consisting of the pure metal in the 

 form of an undercooled liquid of extremely high viscosity. As such 

 an intercrystalline amorphous cement might be expected to have a 

 vapour-pressure higher than that of the crystalline form, experiments 

 were carried out to determine if, upon heating in a vacuum, a greater 

 loss of weight occurred in fine-grained specimens than in coarse-grained 

 specimens. The fine-grained specimens would naturally contain a 

 greater proportion of the intercrystalline cement. Aluminium, anti- 

 mony, and cadmium gave inconclusive results, but with copper, silver, 

 and zinc the finely crystalline specimens gave a greater loss of weight 

 on heating in a vacuum, at temperatures up to about 100° C. below 

 their melting points, than coarsely crystalline specimens. The struc- 

 tures developed by " vacuum-etching " and the formation of twinned 

 crystals in silver are described and illustrated by photomicrographs. 



* Journ. Inst. Metals, viii. (1912, 2) pp. 222-17 (14 figs.), 

 t Zeitschr. Anorg. Chem., Ixxviii. (1912) pp. 201-12 (20 figs.). 

 X Int. Zeitschr. Metallographie, iii. (1912) pp. 179-94 (11 figs.). 

 §^Journ. Inst. Metals, viii, (1912, 2) pp. 149-85 (11 figs.). 



