ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 673 



carbon, 0*1 to 0*2 p.c. silicon, and 0*03 to 0*18 p.c. manganese, into 

 malleable cast iron by heating in oxide of iron at about 1000° C. In 

 samples withdrawn after different periods, estimations of carbon at dif- 

 ferent depths and mien iscopic examination showed that the carbon content 

 increased gradually with the depth, passing through a pearlite zone of 

 constant composition. The chief factor in decarburisation is the dif- 

 fusion of oxidising gases from the iron oxide into the interior, but 

 the diffusion of carbon from the interior outwards also plays a part. 

 The statement of Wrist,* that the formation of temper-carbon from 

 cementite is a necessary preliminary to decarburisation is disputed. 



Decarburisation of Iron-carbon Alloys.f — W. H. Hatfield disagrees 

 with Wiist's view that in the decarburisation of white iron the carbon 

 must lie precipitated as temper-carbon before it is eliminated. Pieces 

 of cemented Swedish bar-iron containing 1 * 64 p.c. carbon, all combined, 

 were packed (1) in charcoal, (2) in sand, (3) in iron ore, and heated 

 slowly. The temperature was maintained at 890° C. for 2-1 hours, then 

 raised to 960 0., where it was kept f or 4<s hours. The temperature then 

 fell very slowly. In (1) the carbon content was unchanged, in (2) it had 

 fallen to 0*75 p.c., in (3) to 0*15 p.c. No temper-carbon could be found 

 in any of the three samples, either by chemical analysis or microscopic- 

 ally. Carbon may therefore be eliminated without previous formation 

 of temper-carbon. The examination of white iron at different stages in 

 its conversion to malleable iron fully confirmed this view. 



Progress in Metallography.} — E. Ileyn reviews the output of re- 

 search in metallography and related subjects, from the Brussels Congress 

 of 1906 up to the beginning of 1909. A comprehensive list of papers 

 published is given, with valuable explanatory and critical comments. The 

 papers are classified as dealing with : — 1. Researches for establishing the 

 chemistry of intermetallic compounds, chiefly by the determination of 

 equilibrium diagrams of systems of alloys, without regard to their 

 practical utility. 2. The iron-carbon system. 3. Iron and manganese 

 alloys, including special steels. 4. Alloys of industrially useful metals 

 other than iron. 5. Metallographical investigation of phenomena in 

 the manufacture of metals other than iron. Friedrich's studies relating 

 to the formation of matte and speiss are examples. 6. The phase theory, 

 physico-chemical methods, crystallography, etc. 7. Accessories for me- 

 tallographical work. 8. Industrial application of metallography. 



Metallographic Notes. § --K. Friedrich ranges over a variety of 

 subjects. The employment of ultra-violet light for photomicrography 

 does not offer advantages commensurate with the increased difficulties 

 of manipulation. Some questions arising in the study of the nickel- 

 cobalt-arsenic alloys are dealt with. No evidence was found for the 

 existence of a compound Ni 2 As. 



* See this Journal, 190S, p. 258. 



t Journ. Iron and Steel Inst., lxxix. (11)09) pp. 242-60 (7 figs.). 

 X Proc. Int. Assoc, for Testing Materials, No. 5 (1909), 20 pp. Report pre- 

 sented to the 5th Congress, Copenhagen, September, 1909. 

 § Metallurgie, v. (1908) pp. 593-604 (16 rigs.). 



