322 DR. WALTER ROSENHAIN AND MR SYDNEY L. ARCHBUTT ON THE 



was required in order to render intelligible the nature of the various heat evolutions 

 and their mutual relations; it will, however, be more convenient to describe this 

 further experimental work by first giving the equilibrium diagram finally arrived at. 

 It will then be possible to discuss each group of alloys and the reactions which they 

 undergo, and to give in detail the evidence upon which the position and interpretation 

 of each line of the diagram is based. 



The equilibrium diagram of the aluminium-zinc alloys is shown in fig. 4, where 

 the concentration of aluminium is plotted horizontally and temperature is plotted 



ft* 



aw- 



f>. 



4. 



34 



t 



r* 1 



603- 



.fil'C 



MO "6 



if. 



H 



fJ 



Fig. 4. 



vertically in the usual manner. The observed temperatures of arrests or retardations 

 on the cooling-curves are shown as crosses, while the results of quenching experiments 

 are indicated by dots surrounded by small circles or squares. The points plotted 

 include all those observed. 



The liquidus, or curve of initial freezing, is represented by the line ABCD ; this 



* only very slightly from the corresponding curve in the diagram of SHEPHERD,* 



e diagram of SHEPHERD did not show the small break in the liquidus at the 



The evidence for the existence of this break in the liquidus lies in the first 



the accuracy with which the observed points on the liquidus have been 



SHEPHERD, Aluminium-Zinc Alloys," 'Journal of the Physical Society,' 1905, 9, p. 504. 



