278 



Dr. W. C. Anderson and Mr. G. Lean. [June 16, 



The curve shown in Diagram 1 is obtained by means of a direct- 

 reading Le Chatelier pyrometer. The platinum-rhodium couple was 

 wrapped in a thin covering of asbestos paper, worked into a pulp and 

 dried, and then placed in the thoroughly liquid mixtures of aluminium 

 and tin. The quantities of metal used were the same throughout, and 

 the conditions of experiment were arranged so that the radiation was 

 similar in each case. The curve ABCDEF shows the position 



500 



400 



300 



00 



%AL 



DIAGBAM 1. Aluminium-Tin Alloys. 

 80% 60% 40% 20% 



o%AL 



of the first halt in the cooling curves of the alloys lying between 

 100 per cent, aluminium and 9 per cent, aluminium. It is, therefore, 

 the liquidus curve, or freezing-point curve. In each experiment the 

 point of temperature was noted at which the retardation of the fall in 

 temperature ceased and the rate of cooling became once more normal. 

 These temperatures are plotted on the line HKLM, which may, 

 therefore, be regarded as approximating to the points at which active 

 separation of solid matter ceased in each of the alloys. It thus 

 indicates the trend of the solidus curve of the series. 



The positions occupied by this first break point in the several alloys 



