Influence of Atomic Weight. 473 



N _ N 

 compounds, ( I . The nitro-compounds of the phe- 



v H H ' 

 nols also always have a slight colour, the N and being united 



thus, ( — N^ | \ ; an( i on reduction this becomes ( — N\g L 



as in the important series of anilines. (Notes of Prof. Schor- 

 lemmer's lectures on Organic Chemisty, 1871.) 



Electric Conductivity. — Kohlrausch and Grotian, and also 

 Tollinger, have found that the conducting-power of the fol- 

 lowing chlorides when in solution are in the order repre- 

 sented below, beginning with the highest in each class : — 



KC1, 



NaCl, 



LiCl. 



BaCl 2 , 



SrCl 2 , 



CaCl 2 , 



ZnCl 2 , 



MgCl 2 . 





The order of conductivity of the sulphates also appears to 

 be the same as above. We thus see that the conductivity of 

 the salts in the same group, when in solution, diminishes with 

 the atomic weight of the positive element. 



Magnetic and Diamagnetic Powers. — It has been noticed 

 (Watts's Diet. iii. p. 773) that those metals which are highly 

 diamagnetic possess large atomic volumes, whereas those which 

 are highly magnetic have but small atomic volumes. Thus 

 Bi, the most diamagnetic substance known, has the high 

 atomic volume 21*2, whilst Fe, Ni, and Co, which are highly 

 magnetic, have very low atomic volumes, viz. about 3*5. The 

 relative distances between the atoms, however, are not the 

 only cause which conditions the magnetism or diamagnetism 

 of a body ; for there are several well-known exceptions to the 

 above rule, as K and Na, which have large atomic volumes, 

 and are slightly magnetic, while Cu and Zn, on the other 

 hand, have small atomic volumes, and are slightly diamag- 

 netic* For elements belonging to the same group, the 

 diamagnetism appears to increase with the atomic weight : 

 thus 



* In a paper which will be published shortly in the JBer. deut. chem. 

 Ges., I have shown that those elements which belong to MendeljefF's even 

 series (vide supra) are magnetic, whilst those which belong to odd series 

 are diamagnetic. Out of about forty elements to which this rule may be 

 applied there is not a single exception, unless it be Na — which Faraday 

 found to be diamagnetic, and therefore in accordance with the rule, 

 whereas Lamy states that it is first repelled and afterwards attracted by 

 a magnet. 



Phil. Mag. S. 5. Vol. 8. No. 51. Dec. 1879. 2 K 



