538 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Nature of the Cast-irons.* — G-. B. Upton adduces further evidence 

 in support of his modification of the iron-carbon diagram.f The effects 

 of silicon, phosphorus, sulphur, and manganese on total carbon and on 

 graphite-content are analysed and expressed numerically. Grey cast iron 

 has crystalline flake graphite mixed with a metallic matrix, which is a 

 solution of silicon and carbon in y-iron. White cast-iron is a super- 

 saturated solution of carbon and silicon in y-iron. Malleable cast iron 

 has temper-graphite mechanically mixed with a metallic matrix, which is 

 a-iron, ferrite, with more or less pearlite. None of the irons' as cast are 

 homogeneous from crystal to crystal. 



Thermal Treatment, f — L. Guillet indicates the importance of the 

 time effect in the heat treatment of steel. The quenching temperature 

 should exceed the highest critical point, but not by more than 50° C. A 

 method of quenching frequently employed is to heat the steel consider- 

 ably higher than this — say to 900°-950° C— and allow it to cool to the 

 upper critical point before quenching. 



A. Porte vin § discusses the heat treatment of alloys of copper. The 

 properties of some of the copper-tin and the copper-aluminium alloys are 

 modified by quenching. A correlation between the mechanical pro- 

 perties and the micro-structure of cold-worked brass annealed at various 

 temperatures has been established. 



Special Steels. || — L. Guillet states that the alloy steels found to be 

 industrially useful, are nearly all of the pearlitic class. The composition 

 of several of these steels, and their mechanical properties after given 

 treatments, are included. 



Industrial Applications of Metallography.^]"— L. Revillon signifies 

 the directions in which metallography is usefully applied in the manu- 

 facture and employment of bronzes, brasses, and steels. Ferric chloride 

 solution is a o-ood etching; reagent for bronzes and brasses. 



)r> K 



Polishing Metals for Examination with the Microscope.** — A. 

 Kingsbury recommends the use of paraffin-wax as a supporting substance 

 for polishing powders. The polishing discs, grooved on the flat face, are 

 warmed to about 100° C, laid flat, and the melted paraffin is poured on 

 them to a depth of about h in., a removable ring or baud retaining the 

 melted wax. Hard foreign particles settle out before the wax sets. After 

 the hardening of the wax, the discs are placed in the spindle of the 

 polishing machine, and the face of the wax turned flat by a hand-tool. 

 The author uses three grades of emery powder, which are mixed to a 



* Journ. Phys. Chem. xiii. (1909) pp. 388-416 (10 figs.). 



t See this Journal, 1909, p. 114. 



% Rev. de Metallurgie, vi. (1909) pp. 807-9. (Paper presented to the Inter- 

 national Congress of Applied Chemistry, London, 1909.) 



§ Tom. cit., pp. 814-18. (Paper presented to the International Congress of 

 Applied Chemistry, London, 1909.) 



| Tom. cit., pp. 810-13. (Paper presented to the International Congress of 

 Applied Chemistry, London, 1909.) 



% Tom. cit., pp. 819-22. (Paper presented to the International Congress of 

 Applied Chemistry, London, 1909.) 



** Proc. Amer. Soc. Mech. Eng., xxxi. (1909) pp. 615-18. 



