256 AN UNDISCOVERED GAS. 



liave a lower one, seeing that potassium follows argon in the table. 



Farther on in the table there is a similar discrepancy. The row is as 



follows: 



Ag = 108, Cd = 112, In = 114, Su = 119, Sb = 120.5, Te = 127.7, 1 = 127. 



The differences are: 



4.0, 2.0, 5.0, 1.5, 7.2, -0.7. 



Here, again, there is a negative diiference between tellurium and 

 iodine. And this apparent discrepancy has led to many and careful 

 redeterminations of the atomic weight of tellurium. Professor Brauner, 

 indeed, has submitted tellurium to methodical fractionation, with no 

 positive results. All the recent determinations of its atomic weight 

 give practically the same number, 127.7. 



Again, there have been almost innumerable attempts to reduce the 

 differences between tlie atomic weights to regularity by contriving 

 some formula which will express the numbers which represent the 

 atomic weights with all their irregularities. Needless to say, such 

 attempts have in no case been successful. Apparent success is always 

 attained at the expense of accuracy, and the numbers reproduced are 

 not those accepted as the true atomic weights. Such attempts, in my 

 o]^inion, are futile. Still, the human mind does not rest contented in 

 merely chronicling such an irregularity; it strives to understand why 

 such an irregularity should exist. And, in connection with this, there 

 are two matters which call for our consideration. These are: Does 

 some circumstance modify these "combining proportions" which we 

 term "atomic weights'?" And is there any reason to suppose that we 

 can modify them at our will? Are they true "constants of nature," 

 unchangeable, and once for all determined'? Or are they constant 

 merely so long as other circumstances, a change in which would modify 

 them , remain unchanged'? 



In order to understand the real scope of such questions, it is neces- 

 sary to consider the relation of the "atomic weights" to other magni- 

 tudes, and especially to the important quantity termed "energy." 



It is known that energy manifests itself under different forms, and 

 that one form of energy is quantitatively convertible into another form, 

 without loss. It is also known that each form of energy is expressible 

 as the product of two factors, one of which has been termed the "inten- 

 sity factor" and the other the " capacity factor." Professor Ostwald, 

 in the last edition of his Allgemeiue Chemie, classifies some of these 

 forms of energy as follows: 



Kinetic energy is the product of mass into the square of velocity. 



Linear energy is the product of length into force. 



Surface energy is the product of surface into surface tension. 



Volume energy is the product of volume into pressure. 



Heat energy is the product of heat capacity (entropy) into temper- 

 ature. 



