﻿314 Intelligence and Miscellaneous Articles. 



in an air-bath ; and one of them may be lengthened or shortened at 

 pleasure. In the space between them two other prisms for total re- 

 flection are placed, which send the two coloured beams parallel, so as 

 to form two tangential images as in the saccharometer. The tube of 

 fixed length is gradually heated ; and equality in colour is obtained 

 by varying the length of the second tube, which is kept at a tempe- 

 rature of 26°- 7. 



It was previously ascertained that the principle of compensation 

 adopted was applicable ; for two columns of vapour, the one hot and 

 short, and the other cold and long but presenting the same colour to 

 the eye, gave the same spectrum when the same image was examined 

 by a direct-vision spectroscope the refracting edges of which were 

 horizontal. 



Spectroscopic examination showed that the colour of a column of 

 nitrous vapour cannot be compensated by that of a column of liquid 

 peroxide of nitrogen. The spectrum of this latter does not present 

 bands of absorption, only a maximum of intensity in the reddish yel- 

 low. — Comptes Rendus , August 8, 1868. 



ON THE MAGNETISM OF CHEMICAL COMPOUNDS. 

 BY PROFESSOR WIEDEMANN. 



The magnetic deportment of chemical compounds of magnetic me- 

 tals is highly interesting, inasmuch as the metals in them frequently 

 retain to a greater or less extent the magnetism which they possess in 

 the free state, and thus, by a determination of this magnetism, conclu- 

 sions may frequently be drawn in reference to the properties of the 

 metals themselves in their combinations. From this point of view 

 the author had determined in a former investigation the degrees of 

 magnetism of various oxygen and haloid salts of the magnetic me- 

 tals, and had found that in analogous salts of the same metal the product 

 of the atomic weight with the temporary magnetism excited by the unit 

 of magnetizing force in the unit of weight of the salt {that is, the 

 magnetism of an atom of these salts) is almost constant. If this atomic 

 magnetism for ferric-oxide salts is 466, its mean value for chromic- 

 oxide salts is 190 '8, and for protosalts of manganese, iron, cobalt, 

 and nickel the numbers respectively 468, 307, 313, and 142. 



I. Recent investigations, made by an entirely analogous method to 

 the former, have shown that the same deportment also prevails in the 

 oxygen and haloid salts of cerium, didymium, and copper. Retain- 

 ing the former unit, we have for the atomic magnetism in aqueous 

 solutions the numbers — 



Didymium sulphate 104*4 



nitrate. 104*2 



,, acetate. . 105-2 



,, chloride 105*7 



