ROOLOGY AND BOTANY, MICROSCOPY, ETC. 221 



Sulphide Enclosures in Iron and Steel.* — G. Rohl has studied, 

 inicroscopicallj and otlierwise, alloys of manganese sulphide and ferrous 

 sulphide with each other and with pure iron. In seeking for a method 

 of distinguishing the two sulphides microscopically, it was found that 

 1 p.c. solutions of organic acids in alcohol, \\ith five minutes etching, 

 produced considerable darkening of the ferrous sulphide as compared 

 with the manganese sulphide. After preliminary etching with picric 

 acid in alcohol, tempering (heat-tinting) to dark yellow leaves the 

 ferrous sulphide blue and the manganese sulphide a dull whitish. The 

 results obtained with binary alloys of the two sulphides are interpreted 

 as indicating the presence of a compound FegMuoSj which forms a 

 continous series of solid solutions with MnS. Such a sobd solution 

 occurring as inclusions in steel may be mistaken for manganese sulphide. 

 A considerable excess of manganese appears to be necessary in steel in 

 order to prevent the formation of harmful ferrous sulphide. 



Roman Iron.! — H. Bell, H. Louis, and J. E. Stead give some notes 

 on a bloom of iron found in 1909, during the exploration of the Romano- 

 British site of Corstopitum. The bloom was 39 in. long, and tapered 

 from about 7 iii. square at one end to about 4| in. square at the other 

 end. By polishing and etching a complete longitudinal section it was 

 ascertained that the bloom was composed of smaller masses- welded 

 together. These masses differed considerably in composition, some 

 being nearly carbonless iron, others steels containing much carbon. 

 The photomicrographs reproduced show the unusual structure of a 

 region of high carbon content. (Plate YIII.) 



Intercrystalline Fracture of Iron and Steel. i — When a piece of 

 a metal is broken, the fracture normally passes through the crystals 

 and not to any extent along the crystal boundaries. J. C. W. Humfrey 

 has investigated specimens of iron or mild steel, which were remarkably 

 brittle, or became so when annealed in a vacuum, and broke along the 

 crystal boundaries when slightly stressed. The presence of small amounts 

 of carbon-dioxide during annealing promoted the development of inter- 

 crystalline weakness, but when carbon dioxide or other oxidizing gases 

 were present in quantity sufficient to oxidize the surface of the specimen 

 strongly, intercrystalline brittleness was not produced. It is suggested 

 that when nearly pure iron is annealed in a slightly oxidizing atmo- 

 sphere, an oxide of iron, soluble in y-iron, but insoluble in a-iron, is 

 formed. AVhen the transformation of the y-iron occurs on cooling, the 

 oxide is deposited at the boundaries of the a-iron crystals and causes 

 intercrystalline weakness. No microscopic evidence of the presence of 

 this oxide was obtained. 



* Iron and Steel Institute, Carnegie Scholarship Memoirs, iv. (1912) pp. 28-79 

 (35 figs.). 



t Joiirn. Iron and Steel Inst., Ixixv. (1912, 1) pp. 118-33 (16 figs.). 



X Iron and Steel Inst , Carnegie Scholarship Memoirs, iv. (1912) pp. 80-107 

 (20 figs.). 



