ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 559 



" Graphitic " Cast-iron.*— 0. Krohnke has studied the peculiar decay 

 of cast-iron pipes resulting in the so called graphitic condition, in which 

 the material is sufficiently soft to be cut with a knife or even to be crumbled 

 in the fingers. Microscopical examination of numerous specimens has 

 indicated that the change involves the dissolving of the ferrite out of 

 the pearlite and the transformation of the graphite into a grey or white 

 substance designated " graphitite." Cementite and the phosphide eutectic 

 are unaffected, and only grey iron is subject to corrosion of this kind, 

 white iron resisting the corrosive agencies. 



Malleable Cast-iron.f— F. Giolitti, F. Carnevali and G. Tavanti 

 have heated various samples of white cast-iron, grey cast-iron, and steel 

 in different mixtures of carbon monoxide and carbon dioxide, at tempera- 

 turps ranging from 800° to 1050° C, to ascertain the effect on carbon 

 content and carbon condition. It was found that carbon was more 

 readily oxidized when existing as cementite than when in the free state, 

 as graphite or temper carbon. The conditions for effective decarburiza- 

 tion were determined. 



Precipitation of Free Carbon in the Iron-carbon System.:}: — "W. H. 

 Hatfield has submitted a number of alloys of iron and carbon, containing 

 also different percentages of common impurities, to various heat treat- 

 ments. The main conclusion reached is that free carbon is only produced 

 by the decomposition of structurally free carbide of iron. AVhen silicon 

 is the only other element present in the alloy, the carbide contains some 

 silicon. Manganese is largely found in the carbide to the exclusion of 

 silicon. Sulphur also appears to cause the exclusion of silicon from the 

 carbide. The tendency of the carbide to decompose is influenced by the 

 presence in it of other elements. The mechanism of the separation of 

 annealing carbon in high-carbon steel is described. 



Synthesis of Meteoric Iron.§ — C. Benedicks has prepared an artifi- 

 cial plessite (the eutectoid aggregate, kamacite + taenite, of meteoric 

 iron) by cooling an iron-nickel alloy containing 12 p.c. nickel very slowly 

 from the molten state. The results are regarded as confirming the 

 Osmond equilibrium diagram for the iron-nickel system. 



Effect of Galvanizing on Strength of Steel Wire.||— H. Winter has 

 made a microscopical study of galvanized wire. The wire was coated 

 electrolytically with copper and embedded in Rose's alloy ; transverse 

 sections were polish-etched with rouge and a solution of ammonium 

 nitrate. The injurious effect of pickling, the formation of a brittle 

 layer of zinc-iron alloy, the thermal action of too long immersion or too 

 high temperature in the zinc bath, are causes of the reduction of strength 

 which occurs to a very variable extent upon galvanizing. 



Annealing of Steel. ^ — W. Campbell has determined the temperature 

 at which, in a rolled steel containing ' 30 p.c. carbon and having a 



* Metallurgie, vii. (1910) pp. 674-9 (29 figs.). 



t Rass. Min. Met. e Chim., xxxiii. (1910) pp. 1-51, through Journ. Soc. Chem. 

 Ind., xxix. (1910) p. 1456. 



t Proc. Roy. Soc, Series A, lxxxv. (1911) pp. 1-13 (36 figs.). 



§ Rev. Metallurgie, vii. (1910) pp. 1084-6 (4 figs.) and viii. (1911) pp. 85-170 

 (15 figs.). || Rev. Metallurgie, vii. (1910) pp. 1064-74 (15 figs.). 



t Proc. Amer. Soc. Testing Materials, x. (1910) pp. 193-200 (12 figs.). 



2 o 2 



