G72 SUMMARY OF CURRENT RESEARCHES RELATING TO 



distribution of sulphide of manganese may be ascertained by taking a 

 "sulphur print." Baumann's method is to apply a sheet of photo- 

 graphic bromide paper, moistened with dilute sulphuric acid, to the 

 steel. The sources of sulphide and silicate of manganese have been held 

 to be the sulphur, manganese, and silicon present in the steel, and the 

 oxygen of the atmosphere, but the author considers that these enclosures 

 may also arise from the inclusion within the steel of furnace slag, or of 

 siliceous matter picked up by the molten metal in its passage from furnace 

 to ingot mould. 



Sulphur as a Cause of Corrosion in Steel.* — G. N. Huntly has in- 

 vestigated the pitting of a steam boiler. Blisters on the interior surface 

 of the boiler were found to contain a solution of ferrous sulphate, to- 

 gether with free sulphuric acid, and a pit was forming in the centre of 

 each blister. The only possible source of the free acid appeared to be 

 the manganese sulphide in the steel. 



Nickel Steel Injured by Over-heating.j — E. Heyn and 0. Bauer 



have investigated the cause of the tracking in forging of two pieces 

 of steel containing 5*49 p.c. nickel and 0*09 p.c. carbon. Sections 

 polished and etched with copper-ammonium chloride showed a very 

 coarse structure, similar to that of a casting, but no segregation or slag 

 inclusions. The steel became fine-grained when heated at 900° C. for 

 one hour. Forging tests made on pieces heated at different temperatures, 

 lor different lengths of time, showed that the steel cracked on forging 

 when heated above a certain temperature. This limiting temperature 

 was found to depend both on the size of the piece and the duration of 

 heating. 



Cementation.} — In the first and second of these articles F. Giolitti 

 points out the disadvantages involved in the rapid fall of carbon content 

 from surface to interior of steels carburised in the usual way. A more 

 uniform percentage of carbon in the carburised layer may be obtained 

 by employing, as cementation agent, a mixture of carbon monoxide and 

 carbon dioxide, or a hydrocarbon. The composition of the gas mixture 

 is adjusted to give the desired carbon content in the steel. 



The third article, by F. Giolitti and F. Garnevali, deals with the lower 

 limit of the temperature interval within which cementation may be 

 effected. The discrepancy between the author's previous statement that 

 700° C. is the lower limit, and Charpy's results, is explained by the 

 observation that at lower temperatures carbon monoxide acts upon iron, 

 funning an adherent layer, probably a, carbide of iron. This is not 

 cementation in the sense understood by the. authors. 



Malleable Cast Iron.§-- F. Giolitti, F. Carnevali, and G. Gherardi 

 have studied the conversion of cast iron containing 2*9 to 3 "6 p.c. 



* Journ. Soc. Chem. Ind., xxviii. (1909) pp. 339-10. 



t Stahl und Eisen, xxix. (1909) pp. G32-5 (13 figs.). 



X Rend. Soc. Cbim. di Roma, vi. (1908) pp. 337-41, 354-8, 359-63, through 

 Journ. Soc. Chem. Ind., xxviii. (1909) p. 205. 



§ Rend. Soc. Chim. di Roma, vi. (1908) pp. 388-93 ; Atti R. Accad. Liucei, 

 xvii. (1908) pp. 662-7, 748-54, through Journ. Soc. Chem. Ind., xxviii. (1909) 

 1 1]>. 205, 245. 



