ZOOLOGY AND KOTANY, MICROSCOPY, ETC. 409 



Metallography, etc. 



Structure of Electrolytically-deposited Copper.* -A. Sieverts and 

 W". Wippelmann describe the rnicrostrucfcure of copper deposited on 

 iron cathodes, in sheets •1-0*8 mm. thick, under different conditions 

 of concentration, acidity, and current density. The deposited sheets, 

 which usually separated readily from the cathode, were clamped between 

 pieces of pure copper, sawn through, and deeply etched on the transverse 

 section, without polishing. A finely-crystalline deposit is first obtained 

 from an acid solution of copper-sulphate. V-shaped crystallites then 

 grow outwards ; their size at first diminishes with increasing current 

 density, but increases after a certain limit is exceeded. Deposits 

 obtained from neutral sulphate solutions contain cuprous-oxide particles 

 enclosed between the crystallites. Deposits from alkaline solutions of 

 complex copper salts adhere firmly to the cathode, and are apparently 

 structureless. 



Critical Point at 460 C. in Zinc-copper Alloys.f — 0. F. Hudson 

 has made a number of experiments to determine whether the thermal 

 change occurring at 460° C. in copper-zinc alloys containing 63 to 40 p.c. 

 of copper is, as Carpenter holds, a eutectoid inversion of ft into a + y, 

 or is a polymorphic change of ft into ft v The effects of long anneal- 

 ings (for periods up to eleven weeks) at temperatures below the 

 critical point, were that (1) in alloys slightly on the a side of pure ft 

 a very decided increase in the amount of a was observed, after a few 

 hours' annealing : subsequently no further increase in the amount of a 

 was noted ; (2) pure ft showed no sign whatever of breaking down ; 

 (3) in alloys slightly on the y side of pure ft there appeared to be 

 a small increase, which soon ceased, in the amount of y. An in- 

 homogeneous alloy was made by pouring a molten alloy (y), containing 

 40 p.c. copper and 60 p.c. zinc, on to copper which had just solidified in 

 a crucible. When cold, the specimen was cut through, and was found 

 to consist of copper at the bottom and y at the top, with layers 

 of intermediate composition between. The layer of pure ft, with some 

 B + y on one side, and some a + ft on the other side, was cut out and 

 annealed at 435° C. The ft iayer gradually grew at the expense of the 

 a and y, and in thirty-two days increased in width from 0" 05-0 "075 in. 

 During this experiment recrystallization of the ft, by the division of 

 large crystals and the subsequent growth of the small ones formed. 

 was observed. A small piece of copper was immersed in molten zinc 

 at a temperature below 4f>0° C. for thirty-six hours. The whole was 

 allowed to cool, and a section was cut and examined. The copper core 

 was surrounded by a layer of yellow alloy, which in turn was surrounded 

 by a layer of y. It appeared that the yellow alloy, which was sharply 

 separated from the copper, was ft. To test this, the experiment was re- 



* Zeitschr. Anorg. Chem., xci. (1915) pp. 1-45. 



t Jouru. Inst. Metals, xii. (1914, 2) pp. 89- 110 (27 figs.). 



