986 
§ 19. Change in the resistance of pure iron in a magnetic field. 
As experimental material an iron wire from Konrswa, Sweden, was 
used for which we are indebted to the kindness of Prof. C. BENEDICKS, 
Stockholm. On analysis the following impurities were found present 
eek We OR 
3 0007 
B 0,028 
SL 0.014 
Mur 0:03 
thus giving a total impurity of about 0,18 "/,. After analysis the 
wire was drawn by Heraeus to a diameter of 0.1 mm. 
. ° SE LURO0 ; 
Before it was drawn the temperature coefficient was —— = 0.14; 
109890 
4 800 AS 
afterwards it was a hy. 
02890 
The iron wire was wound non-inductively upon an ebonite cylinder, 
and was so placed in the magnetic field as to be perpendicular to - 
the lines of force throughout. The method of overlapping shunts was 
used for determining the resistance. Resistances without field are 
given in Table XXIII. 
TABLE XXI 
Resistance of pure iron as a function 
of the temperature. 
i w 
988.0 K. | 11.18 0 | 
90 2.225 
11.5 1.859 
20.3 | 1.129 
14.5 1.124 
The temperature coefficient of the resistance is very small in the 
liquid hydrogen region; in liquid oxygen and nitrogen it is large. 
Resistances were measured at 288° K., 77° K., 20°,3 K. and 14°,5 K. 
The measurements at 77° K. are not quite trustworthy, and we 
communicate them only because they are sufficiently accurate to 
determine the orientation of the temperature curve, 
