CHEMISTRY OF THE NINETEENTH CENTURY. 629 



in larger quantities. The arrangement is shown in Fig. 316, where is 

 seen a section of a furnace of a glazed porcelain tube passing through 

 it. Within the outer is another tube, A, of porous earthenware. The 

 space a between the inner and outer tube is connected by the tube c 

 with the bottle c, which contains the materials for evolving carbonic 

 acid gas, and at the other end is the exit tube b. When the furnace 

 is in full activity steam is driven into the porous tube by boiling the 

 water in the vessel B, this steam being decomposed by the heat ; the 

 hydrogen for the most part diffuses through the porous tube into the 

 space a, and with the carbonic acid gas passes through the tube b into 

 a solution of potash, which absorbs the carbonic acid and permits the 

 hydrogen to be collected alone. The oxygen is collected chiefly from 

 the central tube in the same manner. We see that in this experiment 

 the porous tube is a filter, as it were, by which the hydrogen is re- 

 moved from contact with the oxygen, and thus recombination in the 

 cooler part of the apparatus is prevented. 



This experiment seems to show that at a certain very high tempera- 

 ture steam would be completely decomposed into its elements, and 

 that at that temperature the two gases might be mixed in combining 

 proportions without combination taking place. If the temperature 

 were allowed to decrease gradually, the gases would combine, passing 

 gradually from a condition in which the vessels contained only a mix- 

 ture of oxygen and hydrogen to one in which it contained nothing but 

 steam, through every intermediate stage in which both steam and un- 

 combined gas are present. These considerations show that chemical and 

 thermic forces are definitely related to each other, and that the quan- 

 tities of the several factors and products of a reaction may exist in the 

 presence of each in proportions varying through an interval of time 

 determined by the surrounding conditions, according to laws which it 

 might be possible to discover. These laws would express the rate at 

 which the chemical action takes place under the given circumstances ; 

 that is, instead of studying merely the final product of a chemical 

 action, we should be studying the progress of the action the forces 

 in the very act of their operation. 



The difference between examining the products only of a chemical 

 reaction and examining the progress of the reaction itself, is analogous 

 to that between statics and dynamics in mechanics. Hence the study 

 of the laws of the progress of chemical reactions is termed chemical 

 dynamics. This mode of investigating chemical phenomena promises 

 to be prolific of results of great importance when it is fully developed. 



Another method of investigation has been applied to the science 

 by the eminent French chemist, M. Berthelot (who must not be con- 

 founded with the older chemist, Berthollet, page 379). In other de- 

 partments of science the forces in operation are reduced to terms of 

 mechanical effort or work; and it is by the same standard, or rather 

 by its equivalent in heat, Berthelot measures the chemical forces which 



