732 PLUCKER ON THE DETERMINATION OF THE 



53. Protoxide of nickel in the hydrate 



54. Protoxide of nickel in a nitric solution 



55. Protoxide of nickel in a muriatic solution 



56. Nickel in the protoxide . . . 



57. ... the hydrated protoxide 



58. ... a nitric solution . . 



59. ... a muriatic solution 



60. Hydrated oxide of manganese . 



61. Protoperoxide of manganese 



62. Oxide of manganese as hydrate 



63. Manganese as hydrated oxide . 



64. ... ... protoperoxide . 



142 

 164 

 171 



45 

 180 

 208 

 217 



70 

 167 



78 

 112 

 232 



24. If we reduce in the same manner the results of the table 

 in paragraph 19, and arrange them beside the corresponding 

 ones which we have previously obtained, we have — 



The agreement of the observations, Mhich were instituted 

 under different circumstances, leaves nothing to be desired if we 

 exclude the micaceous iron ore. As regards powders, a source 

 of error consists in their unequal pressure into the watch-glass ; 

 and since it cannot be admitted that in the two months, during 

 which the powdered micaceous iron ore was exposed to the air, 

 it might have undergone a chemical change, I am inchned to 

 attribute the difference to the former source of eiTor. 



25. Although iron is of itself so strongly magnetic, it loses its 

 magnetism in most of its chemical combinations in so great a 

 degree, that until quite recently, as these were 7ioi attracted by 

 the magnet, they were regarded as not magnetic. I have not 

 yet been able to examine the deportment of the protoxide of 

 iron, nor to determine accurately in what proportion the intensity 

 of the magnetism of iron is diminished in the pure peroxide. On 

 taking different kinds of the peroxide of iron occurring in nature 

 and prepared in laboratories, the results were extremely discord- 

 ant. It might be imagined that the different intensity of the 

 magnetism in the various kinds of peroxide of iron might be con- 



