Effects due to Magnetization. 457 



broken at regular intervals over a considerable time, and curves 

 were drawn showing the variation of the " throw " with time, 

 and the fluctuation of the original deflection caused by this 

 treatment. The strength of field was about 11,000 H, and the 

 experiment was conducted without compensating the original 

 deflection, and by making the field for one minute, then break- 

 ing for one minute, and so on. 



One of the curves is shown in fig. 1, (III) in which positive 

 ordinates are values of the concentration throw at " make," and 

 negative ordinates the values of the " protective throw." 



Experimenting was not begun until the gelatine had com- 

 pletely hardened, and since the electrodes would tend to become 

 polarized while the gelatine was hardening, the "protective 

 throw" was very small, and soon masked by the concentration 

 effects. After about five minutes, making the field had very 

 little effect at all, but began to show decided " concentration 

 throws" ten minutes later, and these rapidly increased with 

 time, as the curve indicates. 



Considering the fluctuation of the original deflection, the 

 effect of this periodic field was to tend to reverse it, just as in 

 the case of the uniform field in experiment B, but much more 

 slowly, since the field was on but half the time in this case. 



The cell also showed the iron salts almost entirely about the 

 point, forming a thick black envelope. 



I. Summary. — The principal results of this investigation 

 may be summarized as follows : 



Whenever iron is exposed to chemical action in a magnetic 

 field, there are two directly opposite influences exerted. 



(a) The direct influence of the magnetized condition of the 

 metal, causing the more strongly magnetized parts to be pro- 

 tected from chemical action. 



This is exhibited in the phenomenon of the " protective 

 throw " which is always in the direction to protect the more 

 strongly magnetized parts of magnetic electrodes. The " pro- 

 tective throw " is small, often requiring delicate apparatus to 

 detect it, and is soon masked by the secondary concentration 

 effects. 



As to the absence of the " protective throw " with acids 

 which attack iron with the evolution of hydrogen, the hydro- 

 gen acts merely mechanically, and when removed by adding to 

 the solution small quantities of hydrogen dioxide, the "pro- 

 tective throw" becomes very decided. 



In the curve, fig. 2 (p. 449), representing the variations of the 

 " protective throw" with the strength of the magnetic field, we 

 trace at once the magnetization of the point electrode. Since 

 only the minute point was exposed to the liquid, it would 



