34 PRINCIPLES OF CHEMISTRY 



As regards those phenomena which accompany chemical action, the 

 most important circumstance in reference to chemical mechanics is that 

 not only do chemical processes produce a mechanical displacement (a 

 visible disturbance), heat, light, electrical potential and current ; but 

 that all these agents are themselves capable of changing and governing 

 chemical transformations. This reciprocity or reversibility naturally 

 depends on the fact that all the phenomena of nature are only different 

 kinds and forms of visible and invisible (molecular) movement. First 

 sound, and then light, was shown to consist of vibratory movements, as 

 the laws of physics have proved and developed beyond a doubt. Then, 

 the connection between heat and mechanical motion and work has 

 ceased to be a supposition, but has become a known fact, and the 

 mechanical equivalent of heat (424 kilogrammetres of mechanical work 

 correspond with one kilogram unit of heat or Calorie) gives a mecha.- 

 nical measure for heat phenomena. Although the mechanical theory 

 of electrical phenomena cannot be considered so fully developed as the 

 theory of heat, nevertheless there can be no doubt but that the elec- 

 trical state of substances, and electric or galvanic currents, represent a 

 peculiar form of motion ; more especially as both statical and dyna- 

 mical electricity are produced by mechanical means (in common elec- 

 trical machines or in Gramme or other dynamos), and, as conversely, a 

 current (in electric motors) can produce mechanical motion, as heat 

 produces motion in heat (steam, gas, or air) engines. Thus by passing 

 a current through the poles of a Gramme dynamo it may be made 

 to revolve, and, conversely, by revolving it an electrical current is 

 produced, which demonstrates tlje reversibility of electricity into 

 mechanical motion. Therefore, chemical mechanics must look for the 

 fundamental lines of its advancement in the correlation of chemical 

 with physical and mechanical phenomena. But this subject, owing to 

 its complexity and comparative novelty, has not yet been subjected to 

 a harmonious theory, or even to a satisfactory hypothesis, and there- 

 fore we shall avoid lingering over it. 



A chemical change in a certain direction is accomplished not only 



as simple as it appears to be, according to this hypothesis, one would expert, for 

 instance, that the compounds of carbon with chlorine would be easily decomposable by 

 reason of the supposed considerable affinity of the separate atoms of carbon, which should 

 therefore tend to mutual combination and the formation of charcoal. It is evident, how- 

 ever, that not only does reaction itself consist of movements, but that in the compound 

 formed (in the molecules) the elements (atoms) forming it are in harmonious stable move- 

 ment (like the planets in the solar system), and this movement will affect the stability 

 and capacity for reaction, and therefore these depend not only on the affinity of the 

 participating substances, but also on the conditions of reaction which change the state of 

 movement of the elements in the molecules, as well as on the nature, form, and inten- 

 sity of those movements which the elements have in their given state. In a word, the 

 mechanical side of chemical action must be exceedingly complex. 



