246 THE POPULAR SCIENCE MONTHLY. 



Avhole length of tlac liquid. This subject has been studied very care- 

 fully, and for a great number of liquids, by Professor HittorflF, of 

 Munster, and Professor G. Wiedemann, of Leipsic. 



Professor F. Kohlrausch, of Wiirzburg, has brought to light the 

 very important fact that, in diluted solutions of salts, including hy- 

 drates of acids and hydrates of caustic alkalies, every atom under the 

 influence of currents of the same density moves on with its own pecul- 

 iar velocity, independently of other atoms moving at the same time 

 in the same or in opposite directions. The total amount of chemical 

 motion in every section of the fluid is represented by the sum of the 

 equivalents of the cation gone forward and of the anion gone back- 

 ward, in the same way as in the dualistic theory of electricity, and the 

 total amount of electricity flowing through a section of the conductor 

 corresponds to the sum of positive electricity going forward and nega- 

 tive electricity going backward. 



This established, Faraday's law tells us that, through each section 

 of an electrolytic conductor, we have always equivalent electrical and 

 chemical motion. The same definite quantity of either positive or 

 negative electricity moves always with each univalent ion, or with 

 every unit of affinity of a multivalent ion, and accompanies it during 

 all its motions through the interior of the electrolytic fluid. This we 

 may call the electric charge of the atom. 



Now, the most startling result, perhaps, of Faraday's law is this : 

 If we accept the hypothesis that the elementary substances are com- 

 posed of atoms, we can not avoid concluding that electricity also, posi- 

 tive as well as negative, is divided into definite elementary portions, 

 which behave like atoms of electricity. As long as it moves about 

 on the electrolytic liquid, each atom remains united with its electric 

 equivalent or equivalents. At the surface of the electrodes decompo- 

 sition can take place if there is sufficient electro-motive power, and 

 then the atoms give off their electric charges and become electrically 

 neutral. 



Now arises the question, Are all these relations between electricity 

 and chemical combination limited to that class of bodies which we 

 know as electrolytes ? In order to produce a current of sufficient 

 strength to collect enough of the products of decomposition without 

 producing too much heat in the electrolyte, the substance which we 

 try to decompose ought not to have too much resistance against the 

 current. But this resistance may be very great, and the motion of the 

 ions may be very slow so slow indeed that we should need to allow 

 it to go on for hundreds of years before we should be able to collect 

 even traces of the products of decomposition ; nevertheless, all the 

 essential attributes of the process of electrolysis could subsist. If you 

 connect an electrified conductor with one of the electrodes of a cell 

 filled with oil of turpentine, the other with the earth, you will find 

 that the electricity of the conductor is discharged unmistakably more 



