244 PKOGKESS IN CHEMISTRY. 



sub.se(|ueiitly inustcT of the royal mint. Gnihain dlscovcrocl that the 

 rates of diffusion of gases into each other is inversely as the scjuare 

 roots of their densities. For instance, the density of hydrogen being 

 taken as a unity, that of oxygen is sixteen times as great; if a vessel 

 containing hydrogen be made to communicate with one containing 

 oxygen, the hj'drogen will pass into the oxygen and mix with it; and, 

 conversely, the oxygen will pass into the h3^drogen vessel. This is due 

 to the intrinsic motion of the molecules of each gas. And Graham 

 found experimentally that for each volume of oxygen which enters the 

 hydrogen vessel four volumes of hydrogen will enter the oxygen ves- 

 sel. Now, 4=x/16; and as these masses are relatively 1 and 10, and 

 their temperatures are equal, the squares of their velocities are respec- 

 tively 1 and 16. 



COMPLEXITY OF LIQUID MOLECULES. 



The question of molecular complexit}- of gases being thus disposed 

 of, it remains to be considered what is the relative complexity of 

 liquid molecules. The answer is indicated ])y a study of the capillary 

 phenomena of liquids, one method of measuring which is the height of 

 their ascent in narrow or capillar^" tubes. It is impossible in the space 

 at our disposal to enter into detail as to the method and arguments 

 necessary. Suffice it to say that the Hungarian physicist Eotvos was 

 the first to indicate the direction of research, and that Ramsay and 

 Shields succeeded in proving that the complexity of the molecules of 

 most liquids is not greater than that of the gases which they form on 

 being vaporized; and also that certain liquids, e. g., water, the alcohols, 

 and other liquids, are more or less '^ associated;" i. e., their molecules 

 occur in complexes of two, three, four, or more, and as the teuq3era- 

 ture is raised the complexity of molecular structure diminishes. 



As regards the molecular complexitj^ of solids nothing definite is 

 known, and. moreover, there appears to be no method capal)le of 

 revealing it. 



ELECTRO-CHEMICAL THEORY. 



While the researches of which a short account has now been given 

 have led to knowledge regarding the nature of molecules, the struc- 

 ture of the molecule has excited interest since the early years of the 

 century, and its investigation has led to important results. The fact 

 of the decomposition of acidified water by an electric current, discov- 

 ered by Nicholson and Carlisle, and of salts into '•" bases "■ and ""acids" 

 by Berzelius and Hisinger, in 1803, led to a belief that a close connec- 

 tion exists between electric energy or. as it was then t(>rmed, "electric 

 force." and the affinity which holds the constituents of chemical com- 

 pounds in combination. In 1807 Davy propounded the theory that all 

 compounds consist of two portions, one electro-positive and the other 



