Energy and Ft her. 1035 



of iron, calcium, barium, and strontium. (Barker's Chemistry p. 152.) 

 Compare this fact with what is said on page 232 in regard to the prop- 

 erty of sulphuric acid as a ferment. The fermenting power both of 

 the sulphuric acid and the soluble ferment is due to their polar energy. 

 Moreover the occurrence of the acid free in nature suggests its probable 

 agency in the evolution of organic, from inorganic life. 



That chemical affinity is not an original inherent property of matter, 

 is proved b} T its dependence on heat. An affinity which a body has at 

 one temperature is completely lost at another-. Thus sulphuric acid at 

 certain temperatures will, from certain compounds, drive off and take 

 the place of phosphoric acid or boracic acid. But at very high tem- 

 peratures either of these is more powerful than sulphuric acid, and the 

 latter is evaporated and driven off while the former remain to enter 

 into the combination. 



But at extremely high temperatures all chemical attraction is nulli- 

 fied, and all bodies pass into the condition of gases. If steam be 

 heated to a temperature of 3,000 C, it ceases to be steam, and the hy- 

 drogen and oxygen no longer remain united, but are resolved into their 

 elementary atoms, or into hydrogen molecules and oxygen molecules. 

 While thus dissociated, the hydrogen has been separated from the oxy- 

 ' gen through a porous partition, but if the gases are allowed to cool to- 

 gether they will reunite at a lower temperature. Liquids and solids 

 likewise undergo dissociation as well as gases. Some liquids become 

 dissociated by simply warming, while boiling effects the dissociation of 

 many liquids and solids. When any body is made volatile, it is dissoci- 

 ated. Many bodies of all three kinds, gaseous, liquid and solid, renew 

 their combinations upon cooling after they have been dissociated by 

 heat. We may suppose that the shapes of the elementary atoms have 

 not been destroyed, and that when a reduction of temperature takes 

 place again, a part of the heat is absorbed in giving motion to the ether 

 belonging to them, and thus re-establishing their attractive affinity. 

 11 The valence of elements decreases with the increase of temperature." 

 Thus at the ordinary temperature phosphorus unites with chlorine to 

 form phosphorus-pentachloride PC1 5 , and phosphorus is then said to be 

 quinquivalent. But if the temperature .be raised, the phosphorus be- 

 comes trivalent, PC1 3 and Cl being formed from the first named com- 

 pound, the increase of heat nullifying two of the polar bonds. Great 

 heat is the antagonist of chemism. At very high temperatures all 

 chemical bonds are dissolved. But the "valence of an element may be 

 constant towards some elements and variable toward others. Thus the 

 valence "of the members of the chlorine family towards hydrogen and 

 towards most of the so-called metals is constant, while towards oxygen 

 and towards hydrogen and oxygen together, it apparently varies between 



