308 Intelligence and Miscellaneous Articles. 



Although only taken very approximately, these measurements 

 (recorded in the annexed Table) will nevertheless, I hope, suffice 

 to show what relatively great coercive force these metals, especially 

 cobalt, can acquire in a state of purity, when it is known that pure 

 iron, obtained by the same means, gave under the same circum- 

 stances only inappreciable deflections. 



For completeness I add that some examples of cobalt which took 

 only a weak magnetization two years since, when I made these 

 experiments, became strongly magnetized now, without having 

 been annealed, and having lost nothing of their original hardness. 



It would a priori seem that the feeble coercive force of these 

 metals when they issue from the galvanoplastic baths is due to 

 the presence of hydrogen in combination with them, and that as 

 soon as it has disappeared, either by the action of heat or by 

 spontaneous liberation, nickel and cobalt resume their real coercive 

 force. In that case the action of hydrogen would be analogous to 

 that of the metals which are combined with nickel to constitute 

 argentan : it would paralyze their magnetic power. 



Comparative Table of the Coercive Forces of Nickel and 

 Cobalt in different States. 



Deflection in 

 the magnetometer. 



Conditions of the experiments. , * N 



Nickel. Cobalt. 



Immediately after magnetization : 



Bar not annealed . . 2° 15' 5° 30' 



„ annealed '. . 5 20 11 



„ annealed and forged 7 14 45 



Thirty-six hours after magnetization : 



Bar not annealed 1 45 5 



„ annealed 3 30 9 30 



„ annealed and forged 6 14 



Seventy-two hours after magnetization : 



Bar not annealed 1 30 4 45 



„ annealed 3 5 9 



„ annealed and forged 5 30 13 30 



„ annealed, magnetized, and again an- 

 nealed 5 115 



Bar annealed, magnetized, and after- 

 wards forged 25 6 



Comptes Rendus de VAcademie des Sciences, 12th Sept. 1881, 

 t. xciii. pp. 461, 462. 



