ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 641 



displaced towards Ar 1. With the higher carbon steels Ar 3, 2, 1 is 

 lowered as a whole by heating beyond the lowering temperature and 

 produces a single low point. The eutectic composition is the same as 

 for carbon steels. 



Platinum Alloys.* — F. Doerinckel has determined the equilibrium 

 diagrams for the binary alloys of platinum with copper, silver, gold, tin, 

 and lead by thermal methods, confirming the results by microscopical 

 examination. With gold and copper, platinum forms a continuous series 

 of mixed crystals. With silver a similar series of mixed crystals is found 

 from 0-48 p.c. platinum. With lead and tin a number of compounds 

 are formed. Of the three lead-platinum compounds, the formula of 

 one only, PtPb, has been established. PtgSn and PtSn are indicated 

 as the formula of two of the four platinum-tin compounds, while the 

 other two are probably Pt2Sn3 existing in two allotropic modifications, 

 and PtgSng. The relationship of platinum to the definitely electro- 

 positive metals would appear to be more remote than to those of the 

 middle part of the periodic system. All these platinum compounds 

 except Pt Sn appear to decompose on melting, forming a liquid of definite 

 concentration and another solid phase. 



Ternary Alloys of Lead, Magnesium, and Tin.f — A. v. Vegesack 

 devotes the first portion of this paper to a theoretical consideration of 

 the conditions of equilibrium of a ternary system in which two binary 

 compounds occur, but no ternary compounds and no ternary mixed 

 crystals. The three components are assumed to be miscible in all pro- 

 portions in the liquid state, and the compounds to be fusible without 

 decomposition. The numerous types of equilibrium possible are 

 separately considered in two main classes : (1) no mixed crystals are 

 formed ; (2) the two compounds are isomorphous. The author has 

 determined the equilibrium diagram of the lead-magnesium-tin series by 

 thermal analysis of the cooling curves of more than 100 alloys, which 

 were also examined microscopically. The two compounds SnMg2 and 

 PbMg2 which occur in this series form with each other two series of 

 mixed crystals a and fi. These, with the two compounds and the three 

 pure metals, are the only solid phases, a has a limiting concentration 

 (tti) -I'l p.c. Mg, 21 p.c. Sn, 57 p.c. Pb, by weight. With more PbMga 

 the reversible reaction 



mixed crystals aj + melt '^ mixed crystals /8j 



occurs at 570 C. 



It is not possible to give here more than a general outline of this 

 illuminating contribution to the study of ternary alloys. 



Alloys of Antimony with Manganese, Chromium, Silicon, and 

 Tin ; of Bismuth with Chromium and Silicon ; and of Manganese 

 with Tin and Lead. J — R. 8. Williams has determined the equilibrium 

 diagrams for each of these binary systems, and summarises the results in 

 a table which is too lengthy to be reproduced here. 10 p.c. ferric 



* Zeitschr. Anorg. Chem., liv.(1907) pp. 333-6 (23 figs.). 



t Tom. cit., pp. 367-416 (83 figs.). 



: Op. cit., Iv. (1907) pp. 1-33 (34 figs.). 



