ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 261 



ends of the diagram. W. Guertler suggests as an explanation of this 

 discrepancy that the mixed crystals formed during solidification decom- 

 pose at lower temperatures into tin and lead. 



Alloys of Lead with Indium and Thallium.*— N. S. Kurnakow 

 and 8. Zemczuzny have determined the electrical conductivity curve of 

 the lead-indium and lead-thallium systems. The plasticity of the alloys 

 was also studied by determining the pressure required to produce flow 

 through an aperture of given size. The flow-pressure curve was found 

 to follow closely the Brinell hardness curve, and was the reverse of the 

 conductivity curve. The authors conclude that lead and indium form a 

 continuous series of mixed crystals. Lead and thallium form three series 

 of mixed crystals. No compounds occur in either system. 



Aurides of Magnesium. - ) - — CI. G. Urasow has made a careful deter- 

 mination of the equilibrium diagram of the gold-magnesium system. 

 The cooling curves of 109 alloys were taken. In some regions of the 

 diagram inoculation was necessary to prevent supercooling. The com- 

 pounds occurring and their melting points (dystectic points or maxima 

 in the diagram) are Mg 3 Au 818° C, Mg 2 Au 788° C, MgAu 1150° C. ; 

 the compound Mg 5 Au 2 is formed at 796° 0. by a reaction taking place 

 between Mg 3 Au and the liquid. Mg 5 Au 2 exists in two forms, the trans- 

 formation temperature being 721° C. The microstructure of alloys rich 

 is magnesium was sufficiently developed by polishing on wet chamois 

 leather. Sections of the other alloys were etched with hydrochloric 

 acid and bromine. 



Phosphorus Compounds of Cobalt.J — S. Zemczuzny and J. Schepelew 

 have studied the range 0-33 '7 atomic p.c. phosphorus of the cobalt- 

 phosphorus system by thermal and microscopical methods. A dystectic 

 point at 33*33 atomic p.c. phosphorus indicates the compound Co 2 P, 

 melting at 1380° C. ; this compound has a transformation point at 

 920° C. The eutectic contains 19*85 atomic p.c. phosphorus and melts 

 at 1022° C. The hardness of the alloy was measured. Co 2 P was 

 observed as well-defined crystals in sections polished and etched with 

 ferric chloride solution in hydrochloric acid. 



Systems : Tin-sulphur, Tin-selenium, Tin-tellurium. § — W. Biltz 

 and W. Mecklenburg have determined the equilibrium diagrams. The 

 volatility of sulphur restricted the range of the tin-sulphur system in- 

 vestigated to 0-23-4 p.c. sulphur. The compounds occurring and their 

 melting points are SnS, 882° C. ; SnSe, 861° C. ; Sn 2 Se 3 or SnSe 2 , about 

 650° C. ; SnTe, <S00° G. The compounds SnS, SnSe, and SnTe were 

 observed microscopically in sections of the alloys. 



The System Cu 2 S-FeS.||— K. Borneinann and P. Schreyer have de- 

 termined the equilibrium diagram by thermal methods and confirmed it 

 by microscopical examination of the melts after solidification. The 



* Zeitschr. Anorg. Chem., lxiv. (1909) pp. 149-83 (5 figs.). 



t Tom. cit., pp. 375-96 (16 figs.). J Tom. cit., pp. 245-57 (7 figs.). 



§ Tom. cit., pp. 226-35 (7 figs.). 



|| Metallurgie, vi. (1909) pp. 619-30 (22 figs.). 



