ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 371 



the distorted structure of cold- worked material was replaced by a normal 

 granular structure when the temperature of annealing reached or 

 exceeded 520° C. 



Manganese Sulphides and Silicates in Iron and Steel.* — In the 

 course of this investigation D. M. Levy has studied the microstructure 

 of the fused sulphides of iron and manganese, pure and alloyed together 

 in various proportions, and of the sulphides and silicates occurring in 

 pig-irons and steels containing different amounts of sulphur, manganese, 

 and carbon. Manganese sulphide can hold iron sulphide in solid 

 solution up to about 50 p.c. Three varieties of manganese sulphide 

 occurring in iron and steel, differing in their content of iron sulphide, 

 are distinguished ; the dark-coloured variety is the most free from 

 sulphide of iron and is the most infusi1)le. 



Internal Structure of Martensite and Pearlite.f — By the 

 previously-described method of examining serial sections J M. Oknof 

 has studied the structural details of martensite in quenched steels 

 containing 0*5 and O'T p.c. carbon, and of pearlite in the same 0'7 p.c. 

 carbon-steel annealed. The thickness of the layers removed in successive 

 grindings and polishings was as small as O'OOl mm. The martensite 

 was observed to be composed of plane lamellae about O'OOl mm. thick. 

 The pearlite consisted of a ground mass of ferrite in which were 

 embedded curved parallel lamellae of cementite, about O'OOl mm. 

 thick and O'Ol mm. broad. 



Solubility of Iron Carbide in y Iron.§^]Sr. J. Wark has prepared 

 ten pure iron-carbon alloys containing 1'21 to 1"96 p.c. carbon. Small 

 sections of these were heated in a salt bath at 1100° C, cooled slowly 

 to various desired temperatures, quenched in water and microscopically 

 examined. A 4-p.c. solution of nitric-acid in amyl-alcohol was used 

 for etching, and also sodium-picrate solution. From the presence or 

 absence of cementite in the sections of a given alloy quenched at 

 different temperatures, the temperature-limit of solubility of a concen- 

 tration of cementite corresponding to the carbon content of the alloy 

 was determined. Thus the solubility-curve of cementite in solid y-iron 

 in the range 1*2 to 2 • p.c. carbon was determined. The maximum 

 solubility was found to be 1-70 p.c. carbon. The solubility-curve, 

 ascertained by quenching specimens heated slowly to the given tempera- 

 ture, agreed with that determined as above. 



Constitution of Portland Cement Clinker.|| — In the course of this 

 investigation E. Jiinecke has shown by the examination of thin sections 

 by transmitted light that alite (8 CaO, 2 SiOg, AI2O3) has a simple 

 structure ; he concludes that it is a compound. 



* Iron and Steel Institute, Carnegie Scholarship Memoirs, iii. (1911) pp. 260- 

 319 (17 figs.). 



t Metallurgie, viii. (1911) pp. 539-41 (18 figs.). 

 t See this Journal, 1911,' p. 828. 

 § Metallurgie, viii. (1911) pp. 704-13 (14 figs.). 

 II Zeitschr. Anorg. Chem., Ixxiii. (1911) pp. 200-22 (14 figc). 



