660 SUMMARY OF <TJRKENT RESEARCHES RELATING TO 



Metallography, etc. 



Formulae of Metallic Compounds.* — Much of the formerly ac- 

 cepted information regarding the composition of compounds of metals 

 with each other has been derived from the chemical analysis of insoluble 

 residues. W. Guertler points out that the application of the methods of 

 physical chemistry has proved this information to be to a large extent 

 erroneous. While, however, the method of thermal analysis has so largely 

 superseded the older methods, abnormal behaviour of some elements 

 renders conclusions uncertain in some cases ; in these instances chemical 

 methods may be profitably employed. The author discusses the dis- 

 crepancies between the formulae of silicides of copper as given by Philips 

 and by Ruclolfi — the method of residue analysis being used by the former, 

 while the latter employed thermal methods. E. Rudolfi f continues the 

 discussion. 



Selective Colouring.!— R. Bolder remarks on the advance mmetallo- 

 graphic methods resulting from the introduction of Lumiere colour- 

 photomicrography. A section of an 83-p.c. ferro-wolfram, when etched 

 with 2 p.c. hydrochloric acid in alcohol for 30 minutes, showed two 

 constituents. Further etching with a dilute solution of potassium ferro- 

 cyanide in water brought out the duplex character of one of these sub- 

 stances, colouring one of the two constituents of which it was made up 

 a deep blue. 



Cobalt-sulphur Alloys. § — K. Friedrich has studied the equilibrium 

 diagram from 0-35 p.c. sulphur. A eutectic line occurs at 879° C. 

 The constitution of the compounds is uncertain : Co 3 S 2 , Co 4 S 3 , Co 6 S 5 , 

 CoS, are suggested. Iodine in potassium iodide solution and concen- 

 trated nitric acid w r ere used for etching. 



Antimonides of Iron and Cadmium. || — N. S. Kurnakow and 

 N. S. Konstantinow give the equilibrium diagrams of the systems 

 antimony-iron and antimony-cadmium. In the former system the 

 compounds FeSb 2 and Fe 3 Sb 2 occur, and two eutectics. The limit of 

 solid solubility of antimony in iron is about 5 p.c. ; this is confirmed by 

 microscopic examination. In the range 0-70 p.c. cadmium of the 

 antimony-cadmium system, stable equilibrium is obtained by inoculating 

 the melt with crystals of CdSb. If the molten alloys are allowed to cool 

 undisturbed, without inoculation, a labile state is established. The 

 diagram corresponding to labile equilibrium differs from the stable 

 diagram in that both the eutectic and " dystectic " (maximum) tempera- 

 tures are lower. The compounds are CdSb and Cd 3 Sb 2 . Some heating 

 curves were taken. The crystal angles of the compounds of both 

 systems were measured. Characteristic photomicrographs are given. 



Copper-tin Alloys. % — O. Sackur and H. Pick have investigated the 

 action of solutions of lead chloride and other metallic salts upon 



* Metallurgie, v. (1908) pp. 184-6. f Tom. cit., pp. 257-9. 



t Torn, cit., pp. 201-2 (2 rigs.). § Torn, cit., pp. 212-15 (14 figs.). 



|| Zeitschr. Anorg. Chem, lviii. (1908) pp. 1-22 (18 figs.). 



•j Tom. cit., pp. 46-58. 



