EUTECTIC RESEARCH: THE ALLOYS OF LEAD AND TIN. 



117 



the section it was possible to detect the presence of a very slight excess of either of 

 the constituents, thus differentiating between alloys which could not be definitely 

 separated by the indications of the pyrometer alone. It was found that in a small 



300- 



JOO'- 



/ftf- 



/Of- 



*t 



n't 



(f) 



(.1) fi+LifuiJ 



(3) ft 



\ff 



(61 fin + Lia uLal 



\ M/3+uiectic (fi + 



(f) Of + Euieetic 



(1} 



H 



S + Euttdic 



K 



(0 



ro 



io 



V 



3o 



1*0 



io 



fo 



f.o 



io 



+0 



70 



3? 



SO 



10 



10 

 /o 



/oo 

 o 



Fig. 30. 



ingot of such an alloy, particularly if slowly cooled from fusion, there was generally a 

 slight concentration of tin towards the top of the ingot and a corresponding small 

 concentration of lead near the bottom. By the aid of the microscope, however, 

 specimens free from excess of either constituent could be picked out, and these were 

 submitted to careful chemical analysis. The composition as thus determined is found 



to be : 



Lead 37'07 per cent. 



Tin 62-93 



and this result agrees closely with the figures given by GUTHBIE, and derivable from 

 ROBERTS- AUSTEN'S diagram, although it is believed that owing to the greater refine- 

 ment introduced by the use of the microscope the present determination is probably 



