Natural Philosophy

by Wilhelm Ostwald

However that may be, light is an energy which, according to the known laws, travels through space with tremendous rapidity. We will call it radiant energy, since the part optically visible, to which alone the name light in its original sense belongs, represents an extremely small portion of a vast field, the properties of which change quite continuously from one end to the other.

Radiant energy is characterized as an oscillatory or wave-like process. So long as this fact was unknown (up to the beginning of the nineteenth century) it was thought that light consisted of minute spherical particles, which shot through space in a straight line with the tremendous velocity mentioned above. Later, in order to "explain" its wave nature, which in the meantime has come to be recognized, it was assumed to be due to the elastic vibrations of an all-pervading thing called ether, of which we know nothing else. This elastic undulatory theory has been abandoned in our time in favor of an electromagnetic theory supported by quite considerable experiential grounds. Whether it will be spared the fate that has overtaken the older theories (or rather hypotheses) of light cannot as yet be predicted with any degree of certainty.

Radiant energy is of very marked importance in human relations. As light it serves, with the aid of the corresponding receiving organs, the eyes, as a more manifold means of intercommunication between our bodies and the outer world than any other form of energy. The energy quantities penetrating to us from the extreme limits of the world space mark the outermost limits of which we have knowledge in any way whatsoever, and finally the energy quantities radiating to us from the sun constitute the supply of free energy at the expense of which all organic life on earth is maintained. Even the chemical energy stored up in coal represents nothing else than accumulations of former sun radiation, which had been transformed by the plants into the permanent form of chemical energy.

Very recently other newly discovered forms of radiant energy have been added to light. They are produced in manifold circumstances, and some bodies emit them constantly. The scientific elaboration of these extremely manifold and unusual phenomena has not yet been carried so far that they can be reduced to a doubt-free system. But so much, it seems, is already apparent, that they are presumably not purely new forms of energy, but rather very composite phenomena which may yield one or more new energies as component parts. But despite the peculiarity of these new rays, nothing certain has as yet been proved against the law of conservation itself.

53. Chemical Energy.

Since chemical energy is only one of several forms of energy, there seems to be no justification for allotting it to a special science, since all the other forms of energy must be incorporated in physics.

But the actual existence of chemistry as a special science which has already many subdivisions is justified in the first place by the external fact that in practical life and in industry chemistry occupies a very wide field comparable, if not superior, to that of the whole of physics. In the next place, from the psychological point of view, it is found that the chemist's methods of reasoning and working are so different from those of the physicist that a division seems to be in order for that reason also. Finally, there is in the nature of chemical energy itself an important distinction which marks it off from the other forms.

While, for example, there is only one form of heat or of kinetic energy, and in electricity there are only the two forms of polar opposites, chemistry, even after the greatest theoretical reduction, possesses at least about eighty forms. That is, it possesses as many forms as there are chemical elements. The experiential law, that the elements cannot be changed into one another,[H] also limits the corresponding changes of the chemical energies into one another, and thus characterizes the independence of these various forms. From this results a disproportionately greater manifoldness of relations, which find their expression in the many thousands of the individualized chemical substances or combinations.

This great manifoldness and the slight regularity hitherto found in connection with the properties and reciprocal relations of the numerous chemical elements renders modern chemistry more a descriptive than a rational science. It was no more than twenty years ago that an earnest and successful attempt was begun to apply the stricter methods of physics to the investigation of chemical phenomena. These labors, so far as they have gone, have yielded a great many far-reaching and comprehensive principles.

The significance of chemistry in human life is twofold. In the first place the energy of the human body, just as that of all other living organisms, depends chiefly upon the action of chemical energies in the most manifold forms. Of all the physical sciences, therefore, chemistry is the most important for biology, particularly for physiology. In the second place, as I have emphasized a number of times, it possesses the peculiar property which enables it to be preserved for a long time without passing into other forms and being dissipated. Furthermore, energy in this form permits of the most powerful concentration. More of chemical energy can be stored in a given space than of any other form of energy. Both these properties, then, may be considered as the reason why organic beings are constituted chiefly by means of chemical energy. At any rate, it is due to these two peculiarities that chemical energy serves as the primary source for almost all the energy used in industry.