967 



tive opinion, as further experiments are wanting to furnish sufficient 

 grounds for a decision. 



3. "On the Condition of certain Elements at the moment of 

 Chemical Change." By B. C. Brodie, Esq., F.R.S. 



This paper contains an experimental inquiry, founded upon cer- 

 tain theoretical considerations as to the condition of bodies at the 

 moment of chemical change, with the discussion of which the intro- 

 duction is occupied. 



The author considers that the peculiar combining properties of 

 the elemental particles of which chemical substances are composed, 

 are due to a chemical polarity of the acting masses, which takes 

 place at the contact of the bodies, and have only a remote relation 

 to the electro-chemical nature of the isolated element. In support 

 of this view are cited the phsenomena of double decomposition, and 

 the properties of the so-called "nascent" elements, which could 

 never be inferred from the nature of the element when once isolated 

 and formed. Double decomposition the author considers to be the 

 true tj'pe of all chemical action. In the case of the bodies called 

 compound, this polarity is manifested by the division of the sub- 

 stance into two parts, v.'hich are universally considered to stand to 

 one another in a certain positive and negative relation ; and also by 

 the synthesis, which corresponds to this division. 



The object of the paper is to point out that an analogous polar 

 relation exists, at the moment of chemical change, between the par- 

 ticles of which the elemental bodies themselves are composed, of 

 which condition we have evidence both when the isolated element 

 is chemically acted on by other bodies, and also in certain cases of 

 the formation of the element from its compounds, in which we have 

 a division and synthesis of the element corresponding (so far as this 

 polar relation is considered) to the division and synthesis of a com- 

 pound body- The evidence of these statements is, that when the iso- 

 lated element is chemically acted upon, we may observe in it (as mani- 

 fested by its combining properties) the same polar or nascent state 

 as is developed in compound bodies; and also that we have certain 

 remarkable cases of the synthesis of the element, to account for 

 which we must assume the same combining relation between its par- 

 ticles as between the particles of which a compound substance is 

 formed. These statements are supported by numerous instances. 



The experimental inquiry relates to a remarkable case of the 

 formation of oxygen, in which the author considers that the mutual 

 a.ttraction of the particles of that element determines the decompo- 

 sition of the substances from which it is evolved. The experiment 

 in question is the mutual decomposition which the peroxide of hy- 

 drogen and certain metallic oxides, first discovered by Thenard, 

 undergo when in contact. Thus the author regards, in this case, 

 the decomposition of the metallic oxide as a pheenomenon which 

 may be represented thus : — 



H02 4-m02=Ho6o6m=HO + 02 + mO, 



