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VIT. Dilute Solutions of Aluminium in Gold. 
By C. T. Heycock, F.R.S., and F. H. Neville, F.R.S. 
(From the Goldsmiths Metallurgical Laboratory , University of Cambridge.) 
Received June 16,—Read June 25, 1914. 
[Plates 4-5.] 
The following is an account of an attempt we have been making to determine the 
complete equilibrium diagram of aluminium and gold. We have been occupied with 
the problem during the last two years, and, as the experiments consume a great deal 
of labour and time, we are not likely to complete the work for at least another year; 
we therefore venture to ask the Boyal Society to accept a resume of the portion 
which is practically complete. 
The results, in part embodied in the accompanying diagram, are based on two kinds 
of experiment—the tracing of cooling curves and the microscopic examination of 
ingots that have been annealed at certain temperatures, specially treated, and finally 
chilled by sudden immersion in water, the chill preserving to a great extent the 
structure existing a moment before the chill. 
The diagram, fig. 1, is a temperature-concentration diagram, the temperature being 
expressed in degrees Centigrade and the concentration in atomic per cents, of 
aluminium. We also give a table stating the percentage by iveight of aluminium at 
important points. It will be seen that none of the alloys contains more than 5 per 
cent, by weight of aluminium. It may very well be thought that the percentage 
compositions at points, such as b and B, c and C, respectively, differ by amounts 
comparable with possible experimental errors. This is to a certain extent true, but, 
for reasons which we give towards the end of the paper, we think that the only 
probable error of any importance is that we may have slightly overestimated the 
amount of aluminium in the alloys; this error will be of the same sign and almost of 
the same amount for all the alloys, and its only effect will be to shift a little to the 
left the points b, L, and perhaps c, a matter of no importance for our conclusions. 
The points B and, to a less degree, C were determined very exactly in a previous 
research ; b and c were fixed partly from theoretical considerations and partly from a 
minute study of the alloys. 
yol. ccxiv. —a 515. 2 m 2 
Published separately, September 23, 1914. 
