The Gold- Aluminium Series of Alloys. 367 



Yarkand Mission, Second. Scientific Results. Introductory Note and 

 Map. 4to. London 1891 ; Aves, by R. B. Sharpe. 4to. London 

 1891. The Government of India. 



Silver Medal, inscribed Johann Svatopluk Presl : Karl Borivoj Presl. 



Mr. W. T. Thiselton Dyer, F.R.S. 



Twenty- two Volumes, various, viz., seven vols. 4to and fifteen vols. 

 8vo. Also fifty-five parts of 'Philosophical Transactions,' and 

 217 Nos. of 'Proceedings of the Royal Society.' 



The Relatives of the late Mr. W. H. L. Russell, F.R.S. 



January 28, 1892. 

 Mr. JOHN EVANS, D.C.L., LL.D., Treasurer, in the Chair. 



A List of the Presents received was laid on the table, and thanks 

 ordered for them. 



The following Papers were read : 



I. "On the Melting Points of the Gold-Aluminium Series of 

 Alloys." By W. C. ROBERTS-AUSTEN, C.B., F.R.S. Re- 

 ceived January 25, 1892. 



The author has already described and exhibited to the Society a 

 new alloy of gold and aluminium, AuAl 2 , which is remarkable for its 

 intense purple colour. 



The physical constants of the gold-aluminium alloys are being 

 determined and the results will soon be ready for publication, but the 

 series has been found to have one interesting peculiarity which 

 deserves special mention. The author has shown ('Roy. Soc. Proc.,' 

 vol. 49, 1891, p. 347) that the addition of 0'2 per cent, of aluminium to 

 gold produces an appreciable fall in the freezing point, an addition of 

 0-4 per cent, causing a fall of 14'28, or an " atomic fall " of 5'0 C. 



Tliese facts indicated that it was desirable to ascertain what are 

 the melting points of the gold-aluminium series of alloys generally, 

 and this has now been done with the aid of the Le Chatelier thermo- 

 couple used in the way which was previously described (loc. cit.). 



The results show that, although a white alloy, containing 10 per 

 cent, of aluminium, has a melting point which is no less than 417 

 lower than that of gold ; the purple alloy, on the other hand, melts 



2 c 2 



