524 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Influence of Phosphorus on the Iron-carbon System.* — F. Wiist 

 prepared and examined 30 alloys containing phosphorus, increasing from 

 0*02-21 '56 p.c. and saturated with carbon in the molten state. The 

 temperature of commencement of solidification is progressively lowered 

 by increase of phosphorus up to C> ■ 7 p.c, about 27° C. for each 1 p.c. 

 phosphorus. Further additions raise the freezing-point. A pause in 

 the cooling curves at 950° C. is due to the presence of phosphorus ; it 

 increases in intensity up to 6 • 7 p.c, then diminishes, and finally dis- 

 appears at 15 p.c. (Fe 3 P). At this percentage Ar 1 also vanishes ; it is 

 diminished in intensity though unchanged in position by smaller phos- 

 phorus additions. The solubility of carbon in iron is diminished by 

 phosphorus. A ternary eutectic occurs in the iron-carbon-phosphorus 

 system, phosphorus 6 • 7 p.c, carbon 2*0 p.c, iron 91 "3 p.c, melting 

 point 950° C. Its existence and that of the compound Fe 3 P are amply 

 confirmed by microscopic examination. A combined heat-tinting and 

 etching method was used. Some reproductions of Lumiere colour photo- 

 micrographs of sections treated in this way are given, in which the 

 constituents of the ternary eutectic are clearly differentiated. 



Solidification and Melting of Cast-iron. — To determine at what 

 stage in the cooling of molten cast-iron the formation of graphite occurs 

 P. Goerens and N. Gutowskyf have quenched two pure cast irons (carbon 

 3*91 and 4*72 p.c. respectively) at different temperatures, both rising 

 and falling, and studied the micro-structure. Cooling and heating 

 curves were also taken. The authors conclude that graphite formation 

 in pure cast-iron takes place during the eutectic solidification interval. 

 The longer the duration of solidification of the eutectic, the more 

 abundantly is graphite formed. The graphite crystals are larger the 

 more slowly they are formed. The eutectic forming on solidification 

 is cementite-mixed crystals ; graphite results from the decomposition of 

 this cementite. These conclusions (agreeing with Wrist's) are supported 

 by an interesting series of photo-micrographs. 



Binary Systems, Platinum-arsenic and Bismuth-arsenic.J — K. 

 Friedrich and A. Leroux have determined the equilibrium diagrams for 

 the ranges 72-100 p.c. platinum and 85-100 p.c. bismuth. Arsenic- 

 rich alloys were not investigated. The first diagram points to the 

 existence of a eutectic melting at 597° C, containing about 13 p.c. 

 arsenic. Possibly the compound Pt 2 As 3 occurs. There appear to be no 

 mixed crystals. The diagram of the bismuth-arsenic system consists of 

 two horizontal lines, one at 267° C. (melting-point of bismuth), and one 

 between 480-490° C. 



Cobalt-arsenic Alloys.§ — K. Friedrich has determined the equi- 

 librium diagram for the range 0-53*5 p.c. arsenic. The compounds are 

 Co 5 As 2 (a and fi modifications) Co 2 As, Oo 3 As 2 , and possibly CoAs. The 

 pure cobalt used melted at 1494° C. The diagram is too complex for 

 brief description. 



* Metallurgie, v. (1908) pp. 73-87 (38 figs.). 



t Tom. cit., pp. 137-47 (32 figs.). 



j Tom. cit., pp. 150-7 (27 figs.). § Tom. cit., pp. 148-9 (7 figs.). 



