Metals at High Temperatures. 



38T 



sion at 250° falls out of the curve entirely as may be seen at 

 once by calculating - . This exceptional behavior was not 







unexpected, however, on account of the change which takes 

 place in nickel in the neighborhood of 300° where its magnetic 

 properties disappear. 



Below this temperature therefore the formulae 



A 8 = 6*496* + 0-00160t'(fi) 

 A = {13460* + 3-315£ 2 }10- 9 



do not apply : the term in the first power is there smaller while 

 the quadratic term increases. 



6. Constantan (60 Cu, Jfi Ni). 



The electrical conductivity as well as the thermo-electrical 

 properties of constantan are peculiar, but in its expansion it 

 differs little from other alloys. It has a coefficient correspond- 

 ing to about the mean of those of the component metals. 



The bar used was 6 mm in diameter and the scale divisions 

 drawn upon the metal itself as with the earlier metals described, 

 in consequence of which the marks grew fainter as the oxida- 

 tion increased although the observations were only extended to 

 500°. The permanent changes in the total length reached a 

 maximum value of about O01 mm . The length at 0° was 

 483-0 mm . 



The results (Tables Yla and Ylb) may be expressed by the 

 following formulae : 



A s = 7-156* + 0-00194 f (ft) 

 A = {14810* + 4-024* a }10- 9 



Table Yla. 

 Constantan Bar. 



>ept, 24 



>ept. 2! 



17'9° 



1818 MV 

 4036 



17-9° 

 1815 MV 

 2917 

 4007 



M 



(mm) 



1-854 

 2-215 



1-723 

 1-374 

 0-972 



M' 

 (mm.) 



— 0-023 



— 0-125 



0-090 

 0-348 

 0-056 



2 

 (mm.) 



1-831 

 2-090 



1-818 

 1-026 

 1-028 



17-9° 

 1821 MV 

 4036 



17-9° 

 1820 MV 

 2927 

 4011 



M 



M' 



(mm.) 



(mm.) 



1-877 



— 0-057 



2-187 



—o-ioo 



1-750 



0-052 



1-366 



—0-335 



0-956 



0-063 



2 

 (mm.) 



1-820 



2-087 



1-802 

 1-031 

 1-019 



