Properties of the Alloys of Cast-iron and Aluminium. 623 



§ VIII. The Relation between the Temperature of Minimum 



Permeability and the Percentage of Aluminium in the 



Specimens. 



It is not possible to say, with any degree of precision, at 

 what temperature the permeability of a specimen attains its 

 minimum value, as the change of permeability with tempe- 

 rature is very gradual in the neighbourhood of the temperature 

 of minimum permeability. It also appears to depend to some 

 extent on the strength of the field considered, being higher 

 for strong than for weak fields. 



For the specimens so far investigated the following approxi- 

 mate values of the temperature of minimum permeability have 

 been obtained. 



Per cent, of Aluminium. 



Temperature of 

 Minimum Permeability. 



364 

 544 



9-89 

 18-47 



750° C. 

 050 

 450 

 25 



A curve connecting these values is shown 

 This curve will be seen to be a straight line. 



Fisr. 6. 



as 



fig. 6. 



% 800 



5 400 





10 



Per cent, of Aluminii 



^o 



