392 SUMMARY OF CURRENT RESEARCHES 



on the effect of rapid heating and cooling of various metals are described. 

 Quenching lines were produced on the surface of mild steel specimens by 

 a rapid cooling from temperatures below 400° C. Cracks were no't 

 obtained either by quenching or rapid heating. 



Importance of Metallography in the Iron Industry.* — P. Oberhoffer 

 indicates the various directions in which the Microscope may be applied 

 to practical advantage in the iron and steel industry. Photo-micro- 

 graphs illustrating the effect of silicon, phosphorus, and manganese 

 upon size of grain, the changes in structure brought about by heat 

 treatment, the effects of segregation, and other structural features, are 

 given. Further examples are given by E. Heyn,f who also reviews 

 briefly the progress of metallography in Germany. 



Cementation by Solid Carbon.! — G-. Charpy and S. Bonnerot have 

 obtained purely negative results in attempting the cementation of a 

 mild steel with sugar carbon, graphite, and diamond, in the total 

 absence of gas. The metal and the carbon were first heated to 1000° C. 

 in separate tubes, in a vacuum continuously maintained, and were placed 

 in contact after cooling. The temperature was raised to and main- 

 tained at 700° C. in a vacuum, till no more gas could be extracted, and 

 was then kept at 1000° C. for several hours. Microscopic examination 

 of the surface of the steel showed that not the least trace of carbon 

 had been absorbed. The presence of traces of gas was found to bring 

 about cementation with each of the three forms of carbon. 



It now becomes necessary to ascertain if the diffusion of carbon in 

 the interior of cast iron and steel is in any way connected with the 

 presence of occluded gas. 



Composition of Mixed Crystals in Alloys. S— D. Mazzotto describes 

 a new method for determining the composition of mixed crystals 

 deposited by alloys at different temperatures, based on a knowledge of 

 the heats of fusion of the mixed crystals. The method is applied to 

 the following binary systems : — lead-tin, tin-zinc, tin-bismuth, bismuth- 

 lead. 



Sintering-point Curve. ||— The sintering-point of a binary mixture 

 is the temperature at which the eutectic begins to melt, and is readily 

 observed. A. Stock points out that the sintering-point curve of a binary 

 system may be used to determine the composition of any chemical com- 

 pounds formed. The curve shows a sharp cusp directed upwards at the 

 composition corresponding with a compound. 



* Stahl und Eisen, xxx. (1910) pp. 239-43 (27 figs.). 

 t Tom. cit., pp. 243-6 (3 figs.). 

 % Comptes Rendus, cl. (1910) pp. 173-5. 



§ Nuovo Cirn., xviii. (1909) pp. 180-96, through Jouin. Cheni. Soc, xcvi. (1909) 

 pp. "1008-9. 



|| Ber. Deutsch. Chern. Ges., xlii. (1909) pp. 2059-61. 



