954 THERMAL CONDUCTIVITY AND SPECIFIC HEAT OF MANGANESE-STEEL. 



the other data along with it give the specific heat of manganese-steel. The specific heat 

 of iron may be taken as being 0"114 (1 + *0014 t), most experimenters agreeing with 

 this result. 



The following table embodies the mean results of ten experiments on each of the 

 cubes. Temperature excess is in degrees Centigrade ; rates of cooling in degrees 

 per minute : — 





Rate of Cooling. 





Temperature 

 Excess. 





Ratio of these 

 Rates. 









Iron. 



Manganese-Steel. 





20 



102 



0-91 



1121 



40 



210 



1-88 



1-117 



60 



319 



2-87 



1111 



80 



441 



3-97 



1111 



100 



5-78 



517 



1118 



120 



7-22 



645 



1119 



140 



8-76 



7-83 



1118 



160 



1038 



9-27 



1119 



180 



1210 



10-86 



1114 



200 



1398 



12-50 



1118 



220 



15-96 



14-28 



1117 



240 



1817 



16-20 



1121 



The fourth column shows that the ratio of the rates of cooling of the two cubes is 

 very nearly constant. The average value of these numbers may be taken for the 

 purposes of calculation as being very near the truth. This average value is 1*117. 

 Then the specific heat of manganese steel is — 



, m r 

 c = , x- x c 

 m r 



252-25 



x 1117 x 114 (1 + 0014 t) 



259-25 

 - -124(1 + -0014 0- 



Thus the specific heat of manganese-steel is about 1*087 times that of iron, and its rate 

 of rise with temperature is the same as that in iron. 



