ZOOLOGY AND BOTANY, MICIIOSCOPY, ETC. 119 



Metallography, etc. 



Copper-tin Alloys.* — F. Giolitti and G. Tavanti have re-determined 

 the equilibrium diagram of this system, using thermal and microscopical 

 methods. The diagram is regarded as being composed of two distinct 

 parts, corresponding to alloys of the compound Cu 3 Sn with copper and 

 with tin respectively. 



Silver Coinage Alloys.f — E. Pannain has investigated microscopic- 

 ally the effect of working upon a coinage alloy containing 83*3 p.c. 

 silver and 16 "5 p.c. copper. The alloy, etched with concentrated nitric 

 acid, is observed to consist of white crystals of a solid solution of copper 

 in silver, surrounded by a dark eutectic. The crystals become elongated 

 by rolling ; annealing tends to restore the regularity of structure. The 

 actual coining breaks up the crystals and produces a structure sufficiently 

 distinct from that of cast metal to permit of the detection of some false 

 coins by microscopic examination. 



Aluminium-copper-tin System.^— J. H. Andrew and C. A. Edwards 

 have determined the liquidus curves of this ternary system. A diagram 

 of the well-known equilateral triangle type is given, representing the 

 results of freezing point determinations of more than 400 alloys. Each 

 isothermal line passes through points indicating the composition of 

 alloys having the same freezing point. The diagram is held to demon- 

 strate that no ternary compound is deposited from any of the liquid 

 alloys, and that no true ternary phase appears to form above the solidus. 

 The compound Cu 3 Al is remarkably stable. Homogeneous solid alloys 

 containing more than 16 p.c. tin and 12 p.c. aluminium could not be 

 obtained, excessive segregation occurring. Some of the alloys separate, 

 in the liquid state, into tin and a copper-aluminium mixture. 



Lead and Tin Alloys.§ — A. E. Dunstan finds that a wire of lead or 

 tin, or an alloy of these metals, loaded in tension beyond its elastic 

 limit, extends at a steady rate. A " viscous flow " takes place. For 

 any given load a coefficient of viscous traction may be deduced from 

 the rate of flow. While the effect of tin on the mobility of lead is great, 

 the effect of lead on the mobility of tin is small. 



Brass and Copper. jj — The effect of cold working and annealing 



upon the tensile properties and microstructure of brass containing 



67 p.c. copper, 33 p.c. zinc, has been exhaustively studied by Grard. 



A numerical expression of degree of cold working is given bv 



100 (8 - s) _ , . , „ . , , ..,,„" 



— , o being the area of cross-section of the original fully 



o 



annealed strip, s the area of cross-section of the strip after cold-rolling 

 in the direction of its length. The effect of temperature and time of 

 annealing was determined on strips cold worked to 125 on the above 

 arbitrary scale. Annealing below 275° C. has little effect ; between 



* Gaz. Chiin. ltal., xxxviii. (1908) pp. 209-39, through Journ. Soc. Chem. Ind., 

 xxvii. (1908 j p. 1155. 



t Atti R. Accad. Lincei, xviii. (1909) pp. 523-5, through Journ. Chem. Soc, 

 xcvi. (1909) p. 731. 



t Proc. Roy. Soc, Series A, lxxxii. (1909) pp. 568-79 (9 figs.). 



§ Phil. Mag., xvii. (1909) pp. 192-201. 



|l Rev. Metallurgie, vi. (1909) pp. 1069-1113 (69 fige.). 



