TABLE 40 {continued) I0i 



PROBABLE VALUES OF THE GENERAL PHYSICAL CONSTANTS 



Pedes 1 has pointed out that the ratio of the mass of the proton to that of 

 the electron (M p /m a ) is another dimensionless constant which should have 

 some significance, and has found that 



(hc/e 2 ) ( =2v/a) = (Mp/m*) (>- i) 



the left side equals 862.64 ±0.68, the right 858.36 ±0.49 or 862.26 ±0.99 de- 

 pending on whether one uses the spectroscopic or the deflection value of e/m. 

 The agreement is good for the deflection value but poor for the spectroscopic. 



Note. — In evaluating the constants, it has been necessary to calculate auxiliary con- 

 stants, and also to use certain conventional quantities, such as g^ and gn. All such quan- 

 tities are listed in Table 42. 



In addition to constants listed in Table 42 there are many other functions of constants 

 given on page 103 of this table and in Table 42. A number of these derived constants are 

 collected in Table 43. An attempt has been made to include the more important or more 

 frequently used values. The process for obtaining the correct probable error for many of 

 the constants of Tables 42 and 43 is sometimes involved. The various derived constants 

 of Table 43 (and the occasional derived constant appearing on page 103 of this table and 

 in Table 41) are given with one and often two more digits than required by the probable 

 error. Such digits are printed below the line, and have been added that calculations made in 

 different ways shall not introduce any appreciable error. 



e/m always indicates merely the ratio of charge to mass for an electron, in em units; e 

 indicates electronic charge in es units ; mo, electronic mass ; m, the atomic weight of an 

 electron. A more logical but less convenient nomenclature would have been (e/tru>) es 

 units, and possibly (e'/m<>) em units. 



In the quantum relation, e = hv = eV, each side represents energy in ergs, provided 

 all quantities are in abs. c.g.s. units. v/V (=e/h) then measures the frequency in sec." 1 

 associated with one abs. es unit of potential. It is usually convenient to substitute the 

 wave number (V) or the wave length (X) in place of v, and to substitute the number 

 of abs. volts (V") in place of V. (F' = int. volts, throughout this paper). The values 

 of the various ratios, such as v' IV" etc., are given in Table 43. 



An electron which has fallen through one abs. volt of potential is termed an abs. volt- 

 electron ; its energy in ergs and speed in cm • sec." 1 are given in Table 43. Corresponding 

 to any ionization potential of an atom or molecule in volts (V"), there is an energy of 

 ionization (eV") which can be measured in units equal to the energy of a volt-electron, 

 and is so designated. An ionization potential of 10 volts corresponds to an energy of 

 ionization of 10 volt-electrons. Similarly, in the case of molecules, we speak of a 

 dissociation potential of, let us say, 10 volts, and a corresponding energy of dissociation 

 (heat of dissociation) of 10 volt-electrons per molecule. The factor by which this last 

 quantity must be multiplied to give the heat of dissociation in calories per mole is given 

 in Table 43. Unfortunately there has arisen the practise, to which Doctor Birge pleads 

 guilty, of designating the heat of dissociation as 10 volts, instead of stating, more correctly, 

 that the equivalent dissociation potential is 10 volts, or that the heat of dissociation per 

 molecule is 10 volt-electrons. 



The name of the units conforms as far as possible with current practise. Difficulties 

 arise with the unknown dimensions of magnetic permeability n, and specific inductive 

 capacity e. It is customary to indicate these unknown dimensions by the symbols m and e. 

 A given unit, such as the gauss, is applied only to quantities of a given set of dimensions, 

 including n and e. In the present discussion we are concerned only with numerical mag- 

 nitudes and no particular attention has accordingly been paid to this matter of dimensions. 



1 Naturwiss., 16, 1094, 1928. 

 Smithsonian Tables 



