360 Kinetic Energy of Positive Ions emitted by Hot Platinum, 



The value of the gas constant calculated for the same 

 number of particles as those for which R is given in the 

 table is 37 x 10 3 . The agreement is quite satisfactory. The 

 table also seems to show that the mean kinetic energy is 

 independent, or almost independent, of the air-pressure sur- 

 rounding the hot platinum. The fact that the temperatures 

 were so low and so near the chief calibration temperature, 

 that of the melting-point of potassium sulphate, may account 

 for the close agreement in the value of R. The temperature 

 should be accurate to within 0*5 per cent. The range of 

 temperature is about twice as great as is the range of R 

 when expressed as percentage variation. This would lead us 

 to expect that the theoretical formula (2) would hold not only 

 for the temperatures given but also for any temperatures 

 obtainable. To test this experimentally is quite impossible, 

 because of the appearance of the negative electrons at higher 

 temperatures than those given in Table III. 



The value of the mean energy of the ions in terms of the gas 

 constant R may also be calculated from the data in Table II. 

 by the use of equation (13) in the paper by Richardson 

 ■arid Brown (Joe. cit.). That equation reduces to 



R=^-^, (3) 



where t is the time elapsed since the upper plate began 

 charging up, i is the current at zero potential and i the 

 current after time t, c is the capacity of the upper plate, and 

 6 is the absolute temperature. 



Two determinations from one of the sets of data gave 

 4*3 x 10 3 and 4'8 x 10 3 as the value of R. We should expect to 

 get the most accurate and consistent calculated values of R 

 from equation (2). By drawing curves through the points 

 representing the value of the current, and also through 

 those representing the logarithm of the current for different 

 potentials, the errors of single observations are largely 

 eliminated. In addition, equation (3) requires an accurate 

 knowledge of the magnitude of ? , which it is not necessary 

 to know in the use of equation (2). 



Discussion of Results. 



The close agreement between the value of the kinetic 

 energy and that required for thermal equilibrium, would 

 appear to militate against the somewhat prevalent idea that 

 the positive ions arise from chemical action. In that case, we 

 should expect the kinetic energy of the emitted ions to be 



