78(1 SUMMARY OF QUERENT RESEARCHES RELATING TO 



0" 50-0* 65 p.c. combined carbon, 0' 57-0 "64 p.c. manganese, 0'30- 

 - 42 p.c. phosphorus, • 08-0 • 10 p.c. sulphur, 1; 30-1* 51 p.c. silicon. 

 Photomicrographs were taken of specimens (1) as cast ; (2) annealed for 

 1 hour at 600°, 700°, 800°, 900°, and 1000° C. ; (3) quenched in water 

 after 5 minutes heating at 700°, 800°, 900°, and 1000° C. ; (4) quenched 

 after 1 hour heating at temperatures as in (3) : (5) reheated for 1 hour 

 at 400° C. after above quenchings. Kourbatoff's reagent, nitric acid and 

 orthotrinitrophenol in ethyl-alcohol, was used for etching. Austenite 

 was observed in some specimens quenched at 1000 c C. The mechanical 

 properties of these cast irons may be improved either by annealing at 

 900° 0., or by a quenching from 900° C. followed by reheating. 



Separation of Graphite in Cast Iron.* — (I. Charpy has heated 

 powdered white cast iron at temperatures 600°-1200° C. under pressures 

 up to 15,000 atmospheres. The iron was placed in a hollow magnesia- 

 lined steel cylinder, and the pressure applied through pistons, one at 

 each end, through which the electric current for heating the sample 

 passed. In all cases graphite resulted from the decomposition of carbide 

 of iron, at temperatures 700°— 1100° C. 



Solubility of Steel.t — E. Heyn and O. Bauer have further extended 

 the application of their method of investigating the constitution and 

 condition of steel by determining its rate of solution in 1 p.c. sulphuric 

 acid.f The influence of the treatment of steel on its solubility in 

 sulphuric acid is here dealt with. The effect of quenching and sub- 

 sequently reheating to different temperatures was studied with steels 

 containing 0"95 and 0*07 p.c. carbon. The influence of cold working 

 and annealing was determined with steels containing 0'0f>, 0*06, 0*08, 

 and' 0*19 p.c. carbon. Many of the authors' conclusions have been 

 given previously.^ Differential heating curves of steel containing 0*95 

 p.c. carbon, quenched from 900° C, indicate that the bulk of the heat 

 produced by the decomposition of the martensite is evolved below 

 400° C. This points to the segregation of one or more solid bodies, x, 

 the nature of which is doubtful, from the solid solution martensite 

 during tempering up to 400° C. Whether the segregation proceeds 

 ultn i -microscopically or microscopically is an open question. For some 

 chromium-tungsten steels examined, there appears to be a direct con- 

 nection between quenching temperature and solubility in sulphuric acid. 

 Th'e solubility of mild steel in sulphuric acid is increased by cold work, 

 and falls again when the cold worked steel is reheated. Very small 

 amounts of permanent distortion in structural steel can be detected by 

 solubility tests. 



In the correspondence on this paper. 0. Benedicks replies to certain 

 objections raised by the authors to the view that troostite is a colloidal 

 solution, or, to use a preferable term, a colloidal system. H. M. Howe 

 sums up the-evidence for each of the rival theories of the constitution 

 of troostite, the colloid theory and the osmondite theory. Neither 

 theory yet appears to be established or disproved. 



* Kev. Metallurgie, vi. (1909) pp. 983-5 (1 fig.) 



t Journ. Iron, and Steel Inst., lxxix. (1909) pp. 109-241 (53 figs.). 



t See this Journal, 1907, pp. 115-16. J Loc. cit 



