64 On the Specific Volumes of Oxides. 



We deduce the following : — 



1. In strong bases the oxygen possesses a negative volume. 



2. In the oxides of the heavy metals and metalloids the 

 volume of the oxygen is positive. 



3. The earth-metals unite with oxygen without any appre- 

 ciable change of volume; and on this account they form a 

 connecting link between acids and bases. 



4. The higher the specific volume of the metal in the oxide, 

 the more negative is the specific volume of the oxygen com- 

 bined with it ; for instance 



Sp. vol. K = 45'4, 

 Sp. vol. 0=55-4. 



The lower the specific volume of the element, the more 

 positive is the specific volume of the oxygen in the oxide ; for 

 example 



Sp. vol. C=+3-6, 



Sp. vol. 0=+21-2. 



Mendelejeff has published some very interesting obser- 

 vations of this kind in his Russian ' Principles of Chemistry,' 

 pp. 856-859. He gives a very beautiful hypothesis of the 

 mechanical theory of the act of combination. It is not, how- 

 ever, suitable to enter upon these discussions here. 



When we observe the above arrangement in Table II, we 

 notice the following : — The more strongly electro-positive the 

 base which an element forms with oxygen, the greater is 

 the negative value for the volume of the oxygen. It appears 

 as if the negative maximum were reached with caesium. On 

 the contrary, the maximum of positive values is probably 

 attained in the vicinity of fluorine. From this one perceives 

 that the value representing the atomic volume of the oxygen 

 in the oxides can, to a certain extent, be looked upon as the 

 amount of affinity of the metal for the oxygen. 



In the same manner that, in the horizontal series of the 

 periodic system, the electro-negative character increases with 

 the atomic weight, the volume of the oxygen changes from 

 negative to positive. The opposite appears to be the case 

 in the vertical groups — at all events, as regards the even 

 elements. In this matter new researches upon the metals 

 and their oxides would be of considerable interest. 



We cannot conclude without thanking Mr. M. M. Pattison 

 Muir, of Caius College, Cambridge, for his great kindness in 

 supplying us with the material to make our determinations 

 of the specific gravity of bismuth pentoxide. 



