TRANSACTIONS OF SECTION A. 



525 



the substance, and known constants. The accuracy of this relationship has 

 been very carefully tested by experiment. 



The expression obtained for c depends upon the assumptions made as to the 

 nature of positive electricity. Two expressions have been obtained — 



(i) On the assumption that the positive electricity in the atom occupies 

 a volume comparable with that of the atom; (ii) that it is divided 

 into small units comparable in size with the negative electron. 



Experimental determinations have been made of the ratio <p/ \/t for different 

 elements and the corresponding number of electrons calculated. The appended 

 table gives the number of electrons in the atom divided by the corresponding 

 atomic weight. 



It will be seen that the numbers in the first column are practically constant 

 at a mean value — three. The numbers in the second column increase rapidly 

 with the atomic weight. From experiments on the scattering of JRontgen rays 

 it is almost certain that the number of electrons in the atom is proportional to 

 the atomic weight, as given by our first assumption. Thus we conclude that the 

 positive electrification occupies a volume comparable with that of the atom, and 

 that the number of electrons in an atom is three times the atomic weight. 



Ratio of the Number of Electrons in the Atom to Atomic Weight. 



3. On the Attraction Constant of a Molecule of a Compound and its 

 Chemical Properties. By E. D. Kleeman, D.Sc, B.A. 



The writer has previously deduced from surface tension and latent heat data that 



the attraction between two molecules of the same kind is — (2,/Jw ) 2 , where z is the 



distance between the molecules, and 2 %/wi, is the sum of the square roots of the 

 atomic weights of the atoms of a molecule, and K is a quantity whose exact form is 

 not known except that it has the same value for all substances at corresponding 

 temperatures and may therefore be a function of the distance between the molecules 

 and the temperature. The quantity 2 -/to, will be referred to as the attraction 

 constant of the molecule. It was now pointed out that it can be shown strictly 

 mathematically that the law of attraction cannot be completely determined from 

 surface tensions or latent heat data. The law deduced must contain an unknown 

 function of the distance between the molecules and the temperature. It follows, 

 therefore, that if we assume a law of attraction between molecules and deduce from 

 it a formula for the surface tension or latent, and find that it fits the facts, it does 

 not therefore follow that the law assumed is correct. In order to be on safe ground 

 it is necessary that the law deduced should contain an unknown function. Now 

 this is the case with the law given above, the exact nature of K being not known. 

 Further, since K is the same for all substances at corresponding temperatures it does 

 not contain 2 \Zm ]t and the chemical attraction of a molecule is therefore proportional 

 to 2\/w,, and this result should be true. 



The attraction constants of the atoms of a molecule of a compound we would 

 expect to be connected with its chemical properties. Thus the writer found that the 



To 

 properties of the quantity — -=■ of a substance, where To denotes the critical 



2 v w, 

 temperature, run parallel with its purely chemical properties. Thus the value of this 

 quantity is constant for a compound and its substitution products when an atom is 

 1910. M M 



