THEORIES AS TO ACTION OF 



contact with another chemical substance, Liebig's view of the 

 vis inertice to reaction, or, as we would term it, of the resistance 

 being overcome by an enhancing of molecular vibration, fits the 

 facts better than any other theory. 



A concise account of the view can perhaps best be put in 

 Liebig's own words : 



"It is well known that there are chemical compounds of so 

 unstable a nature that changes in temperature and electrical condi- 

 tion, or even simple mechanical friction, or contact with bodies 

 apparently totally indifferent, cause such a disturbance in the 

 attraction of their constituents, that the latter enter into new 

 forms, without any of them combining with the acting body. 

 These compounds appear to stand but just within the limits of 

 chemical combination, and agents exercise a powerful influence 

 on them which are completely devoid of action on compounds 

 of a stronger affinity. Thus, by a slight increase of temperature 

 the elements of hypochlorous acid separate from one another 

 with evolution of heat and light ; chloride of nitrogen explodes 

 by contact with many bodies which combine neither with chlorine 

 or nitrogen at common temperatures ; and the contact of any 

 solid substance is sufficient to cause the explosion of iodide of 

 nitrogen, or of fulminating silver. 



"It is evident that the active state of the atoms of one body 

 has an influence upon the atoms of a body in contact with it ; 

 and if these atoms are capable of the same change as the former, 

 they likewise undergo that change ; and combinations and de- 

 composition are the consequence. But when the atoms of the 

 second body are not of themselves capable of such an action, any 

 further disposition to change ceases from the moment at which 

 the atoms of the first body assume the state of rest, that is, when 

 the changes or transformations of this body are quite completed." 



It is worthy of note, in view of modern opinion upon the subject, 

 that Liebig was well aware of the fact (and actually deprecates 

 the use of the term catalytic force for this very reason), that a 

 catalytic agent need not necessarily start a reaction, but only in- 

 crease the rapidity of one already in progress ; instancing as an 

 example the catalysis of hydrogen peroxide by platinum or silver. 



There is no other theory which appears to the writer to cover 

 the case of detonating substances in which the mechanical per- 

 cussion acts as a catalyst in inducing chemical reaction ; similar 



