CHEMICAL AFFINITY OF ATOMS. 23 



pies of like character, as well as of other transformations, could be readily given 

 in any number. 



Chemical Affinity of Atoms : Relation to Heat. While the force of 

 gravitation acts upon the particles of matter without reference to the 

 character of the body, still another form of force is found in the realm 

 of atoms, which is effective between the atoms of chemically different 

 bodies, namely, chemical affinity. This is the force by means of which 

 the atoms of chemically different bodies unite in chemical combination. 

 The energy itself is extremely variable between the atoms of different 

 chemical bodies. 



A distinction is made between strong chemical affinities (or rela- 

 tions) and weak affinities. Just as it is possible to determine the kinetic 

 energy of a body in motion from the amount of heat that it generates 

 in its impact upon an unyielding surface, so the degree of chemical 

 affinity can be determined from the amount of heat that is produced, 

 as the atoms of chemically different bodies unite in chemical combina- 

 tion; for if a complex body is formed from individual, chemically 

 different atoms heat is, as a rule, generated. If as a result of the 

 force of affinity the atoms of i kilo of hydrogen and 8 kilos of oxygen 

 unite to form the chemical combination water, an amount of heat is 

 generated that is equal to that developed by the impact of a weight of 

 47,000 kilos in falling from a height of 300 meters above the surface of the 

 earth. One gram of hydrogen converted into water by addition of 

 oxygen yields 34,460 heat-units (calories). One gram of carbon con- 

 verted into carbon dioxid yields 8080 calories. 



Whenever in the course of chemical processes considerable affinities 

 are satisfied heat is set free, that is, generated from the force of affinity. 

 The force of affinity is a form of potential energy acting between the 

 various atoms that in the course of the chemical process is transformed 

 into heat. It is thus likewise explicable that in the course of those 

 chemical processes through which strong affinities are dissolved, in 

 which the chemically united atoms are again separated, cooling takes 

 place, or, as is commonly stated, heat becomes latent. That is, the 

 energy of the heat rendered latent is transformed into chemical poten- 

 tial energy, and this in turn, after disintegration of the complex chemical 

 body, appears between its isolated, individual atoms as chemical affinity. 



LAW OF THE CONSTANCY OF ENERGY. 



Julius Robert v. Mayer (1842) and Hermann Helmholtz (1847) have 

 'established the important law that in a system that receives no influ- 

 ence or impression from without the sum of all the contained kinetic 

 energies is always equal. The energies may be transformed one into 

 another, so that the potential energy may be converted into kinetic 

 energy, and the reverse, but never is even the slightest amount of the 

 energy lost. The transformation that takes place in the energies 

 occurs in a definite manner, so that from a definite measure of a given 

 force an equally definite measure of the new-appearing force always 

 results. . 



The forces occurring in the animal organism appear in the following 

 modifications : 



i. As movement in mass (generally designated simply movement), 



