300 



MAGNETIC METHOD 



[Chap. 8 



degrees (keeping its distance from the magnetometer the same), and the 

 deflection is again observed. 



If the specimen is placed in the first Gauss position (that is, the magnetic 

 needle in the extension of the magnet) with respect to the magnetometer, 

 if its equivalent magnetic moment is Af = dv, where v is its volume and d 

 the intensity of magnetization, the apparent change in magnetic intensity 

 is e(s - .So) = AH = 2M/7', so that 



s — So = di, 



(8-7) 



where c = 2v/er , e is the scale value (see page 323), So is the reading without 

 the specimen, and s the reading with the specimen. If residual magnetism 



Fig. 8-2. General hysteresis curve. 



is present, its component in the longitudinal direction of the specimen will 

 be added to the induced magnetism (reading: S\). After the specimen has 

 been reversed, the component of permanent magnetization opposes the 

 induced magnetization (reading: 52). Then with di as the induced, and dr 

 as the residual magnetization: 



c3i = — - — — So 



and 



) (8-8) 



Cdr = '^ 



2, Quantitative determinations of induced magnetization may be made after 

 residual and induced magnetizations have been separated. It is conven- 



