222 CHEMICAL TRANSFORMATIONS. 



together only by a weak affinity. It is well known 

 that there are chemical compounds of so unstable a 

 nature, that changes in temperature and electrical 

 condition, or even simple mechanical friction, or 

 contact with bodies of apparently totally indifferent 

 natures, cause such a disturbance in the attraction 

 of their constituents, that the latter enter into new 

 forms, without any one 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 com- 

 pounds of a stronger affinity. Thus, by a slight 

 increase of temperature, the elements of hypochlo- 

 rous 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 nor nitrogen at common tempera- 

 tures; and the contact of any solid substance is 

 sufficient to cause the explosion of iodide of nitro- 

 gen, or fulminating silver. 



It has never been supposed that the causes 

 of the decomposition of these bodies should be 

 ascribed to a peculiar power, different from that 

 which regulates chemical affinity, a power which 

 mere contact with the down of a feather is 

 sufficient to set in activity, and which, once in 

 action, gives rise to the decomposition. These 

 substances have always been viewed as chemical 

 combinations of a very unstable nature, in which 



