ELECTRONIC THEORY OF ELECTRICITY. 7 



up hydrogen at the negative electrode, we find that to evolve a volume 

 of one cubic centimeter of hydrogen gas at 0° C. and 760 mm. we have 

 to pass through the electrolyte a quantity of electricity equal to 8.62 

 coulombs. For 96,540 coulombs are required to evolve one gram 

 of hydrogen and 11,200 cubic centimeters at 0° C. and atmospheric 

 pressure weigh one gram. The number 8.62 is the quotient of 

 96,540 by 11,200. 



Various arguments, some derived from the kinetic theory of gases, 

 indicate that the number of molecules of hydrogen in a cubic centi- 

 meter is probably best represented by the number twenty million 

 million million =2 X 10 19 . Hence it follows, since there are two 

 atoms of hydrogen in a molecule, that in electrostatic units the electric 

 charge on a hydrogen atom or hydrogen ion is 



96540 x 3 x 10 9 65 , 



11200 x 4 X 10 19 = 10" electrostatic unit 



22 

 = TT^n of a coulomb. 

 10 ° 



Accordingly, if the above atomic charge is called one electron then 

 the conventional British Association electrostatic unit of electric 

 quantity is equal to 1540 million electrons, and the quantity called a 

 coulomb is nearly five million million million electrons. The electron 

 or the electric charge carried by a hydrogen atom or ion is evidently 

 a very important physical constant. If we electrolyze, that is decom- 

 pose by electricity aqueous solutions of various salts, such as sodium 

 chloride, zinc chloride, copper sulphate, silver nitrate, we find, in ac- 

 cordance with Faraday's Laws of Electrolysis, that the passage of a 

 given quantity of electricity through these solutions decomposes them 

 in proportional amounts such that for every 46 grams of sodium 

 liberated there are 65 of zinc, 63.5 of copper and 216 of silver. 

 These masses are called chemical equivalents. Accordingly, if we 

 imagine a number of vessels placed in a row containing these solutions 

 and by means of platinum connecting links or plates we pass an electric 

 current through the series, for every atom of copper or zinc carried 

 to their respective kathodes, we shall have two atoms of silver or 

 sodium similarly transported. Since the same quantity of electricity 

 must pass through every vessel in the same time it is evident that the 

 above fact may be interpreted by assuming that whilst an atom of 

 silver or sodium acting as an ion carries one electron, an atom of zinc 

 or copper carries two electrons. 



In the same way we may have atoms which carry three, four, five 

 or six electrons. Thus we may interpret the facts of chemical 

 valency and Faraday's Law of Electrolysis in terms of the electron. 



