296 ADVANCED ELECTRICITY AND MAGNETISM. 



no deflection of the particles which are being studied. When 

 this condition is realized, the force qe with which the electrical 

 field acts on the moving particles is equal and opposite to the 

 force gvh with which the magnetic field acts on the moving parti- 

 cles, so that, disregarding sign, we have 



qe = gvh 

 or 



that is to say, the velocity of the particles is equal to the ratio 

 of the electric field intensity e in abvolts per centimeter to the 

 magnetic field intensity h in gausses, on the condition that the 

 fields together produce no deflection of the moving particles. 



" Electrochemical equivalent " of a- and /3 -particles. Accord- 

 ing to the dissociation theory of electrolysis each atom of hydrogen, 

 for example, in a dilute solution of sulphuric acid is isolated and 

 carries a definite amount of charge, and the ratio m/q is called 

 the "electrochemical equivalent" of hydrogen, where m is the 

 mass of a hydrogen atom (ion) and q is the charge upon it. 

 The ratio (m/q) of the mass of a gas ion to the charge upon the 

 ion is called the "electrochemical equivalent" of the gas ion. 

 This ratio is determined by equation (3) or (4) when the electric 

 or magnetic deflection of the particle has been observed and when 

 the velocity of the particle is known. The value so determined 

 is given in grams per abcoulomb and it is equal to 5.36 X io~ 8 

 grams per abcoulomb for the 0-particles (electrons), from which 

 it follows that the particles have a mass 1/800 as great as the mass 

 of a hydrogen atom if the charge q is the same in both cases.* 



* In regard to the equality of charge on mono-valent ions in electrolytes and on 

 gas ions, see Oliver Lodge's Electrons, pages 77-90. where a simple account is given 

 of the work which has been done by J. J. Thomson in the determination of the 

 value of q (or m). 



