V. Gold-Aluminium Alloys. 

 By C. T. HEYCOCK, F.R.S., and F. H. NEVILLE, F.R.S. 



Received October 31, Read December 7, 1899. 

 [PLATES 4-5.] 



THIS paper is a study of the binary alloys composed of gold and aluminium. The 

 fact that metals in many cases form definite chemical compounds with each other, is 

 becoming increasingly evident as attention is given to the subject. But there are 

 many pairs of metals whose freezing point-curve affords no indication of chemical 

 combination, and which probably do not combine with each other under the conditions 

 of our experiments. It is therefore desirable, in seeking for such compounds, to 

 select a pair of metals which are known to have a peculiar relation to each other. 

 We chose gold and aluminium for several reasons. First, on account of the beautiful 

 purple compound of Sir W. ROBERTS- AUSTEN, and on account of our own experiments 

 ('Journal Chemical Society,' voL 74, 1894), which showed it to be a very stable body 

 in solution. There was also the important point that the alloys of gold and aluminium 

 admit of fairly rapid analysis by the determination of the gold. 



In the present paper the freezing point method is combined with a microscopic 

 study of the alloys, and we hope that it will be found that the interpretation of the 

 results is more conclusive than in previous papers of our own and of others in which 

 only the one method or the other was employed. 



Section I. describes the methods of experiment. 



Section II. contains tables of freezing points, figures of the freezing point-curve, 

 and an account of the curves. 



Section III. is devoted to a description of the microscopic appearance of the alloys, 

 and is illustrated by photomicrographs. 



SECTION I. 



In the experiments on which the freezing point-curve is based, the method of pro- 

 cedure was similar to that described in our paper (' Phil. Trans.,' A, vol. 189, p. 25) 

 on the freezing point of copper tin, silver copper, and other alloys.* The freezing 

 point of pure gold was first determined, and then successive roughly weighed 

 amounts of aluminium were added, the freezing point being taken after each addition. 



* For the method of determining temperatures, sec also our paper (' Journ. Chem. Soc.,' 1895, p. 160). 

 VOL. CXCIV. A 256. 2 D 11.4.1900 



