258 SUMMARY OF CURRENT RESEARCHES RELATING TO 



line structure of metals, and illustrates the paper- with an instructive series 

 of photomicrographs. A molten metal, on cooling to its freezing-point, 

 starts to crystallise from centres which are more numerous as the speed 

 of cooling is greater. Thus rapid freezing produces a small grain. In 

 impure metals the greater purity of the first forming dendrites produces 

 irregularity in composition in the solid metal ; this may be rendered 

 visible in etched sections. In pure metals the orientation within each 

 grain may be revealed by deep etching, developing etching-pits and 

 secondary crystals. The influence of mechanical distortion and of 

 annealing was investigated. The author describes the crystalline 

 structure of aluminium, antimony, bismuth, cadmium, copper, gold, lead, 

 nickel, platinum, silver, tin, and zinc. 



Theory of Malleableising.* — F. Wrist found that in cast iron 

 containing 4 p.c. total carbon, 1 p.c. silicon, with very small amounts of 

 other impurities, 3' 4 p.c. temper carbon was formed by heating in 

 vacuo for two hours at 950° C. Weighed quantities of the cast iron 

 and of dried iron oxide, contained in separate porcelain boats, were 

 heated in a previously evacuated tube in a Heraeus furnace. Samples 

 of gas formed could be drawn off and analysed. The author gives the 

 results obtained, from which he concludes that malleableising proceeds 

 through the combination of oxygen with temper carbon (formed by 

 annealing) giving CO.,, which then penetrates the iron and forms CO 

 with more temper carbon. The CO then takes oxygen from the ore, 

 which is reduced, and C0 2 is again formed. If the supply of oxygen 

 from the ore fails, C0 2 ceases to be re-formed, and the iron may even 

 be re-carburised by the decomposition of CO into C0 2 and C. Photo- 

 micrographs and diagrams illustrate the paper. 



Melting Point Diagram of Nickel - sulphur Compounds.! — 

 K. Bornemann gives the equilibrium diagram of the nickel-sulphur 

 system from 0-31 p.c. sulphur. A homogeneous melt is obtained in 

 this range. The only compound stable in the molten state is Ni 3 S 2 , 

 melting-point 787° C. Others exist at lower temperatures. Ni 3 S 2 and 

 nickel form two series of mixed crystals ; the eutectic of the two 

 saturated solid solutions melts at 644° C. The thermal results were 

 microscopically confirmed. 



Steel and Meteoric Iron.f—F. Berwerth describes the structure of 

 meteorites, with special reference to the Vienna collection, and points 

 out that meteoric iron may be regarded as a variety of steel. Kamacite, 

 taenite, and plessite are the three chief constituents, all containing 

 nickel. A plate of Toluca meteoric iron was kept at 950° C. for seven 

 hours and slowly cooled. The kamacite was then found to have changed 

 into a finely-granular aggregate. The author proposes to distinguish 

 meteoric irons, whose structure has been changed by heating within 

 terrestrial space, as metabolites. Such meteorites have a finely- 

 granular fracture, differing greatly from the usual coarsely crystalline 



* Metallurgie, v. (1908) pp. 7-12 (16 figs.). 



f Tom. cit., pp. 13-19 (20 figs.). 



X Journ. Iron and Steel Inst.,lxxv. (1907, 3) pp. 37-51 (5 figs.). 



