260 INORGANIC CHEMISTRY 



stated the general question, it may conduce to clearness if some 

 details are given. 



(1) The variation of molecular surface-energy with temperature is 

 such that the surface-energy, for equal numbers of molecules distrib- 

 uted over a surface, is equal for equal intervals of temperature below 

 the temperature at which surface-energy is zero that is, the critical 

 point. This gives a means of determining the molecular weights of 

 liquids, and we assume that the molecular weight of a compound is 

 accurately the sum of the atomic weights of the constituent elements. 



(2) The volume-energy of gases is equal at equal temperature from 

 that at which volume-energy is zero i. e., absolute zero. And it fol- 

 lows that those volumes of gases which possess equal volume-energy 

 contain equal numbers of molecules again, a close connection with 

 atomic weights. 



(3) The specific heats of elements are approximately inversely pro- 

 portional to their atomic weights; and of compounds to the quotient 

 of their molecular weights divided by the number of atoms in the 

 molecule. Specific heat and entropy are closely related ; hence one of 

 the factors of thermal energy is proportional (nearly) to the recipro- 

 cal of the atomic weights. 



(4) The ion carries in its migration through a solution one or more 

 electrons. Now, the ion is an atom carrying one or more charges 

 one for each equivalent. Here we have the capacity for electric charge 

 proportional to the equivalent. 



(5) The factors of chemical energy are atomic weight and chemical 

 potential; and as the former is identical numerically, or after multi- 

 plication by a simple factor with equivalent, electric potential is pro- 

 portional to chemical potential. 



We see, therefore, that surface, volume, thermal, electrical, and, no 

 doubt, other forms of energy have as capacity factors magnitudes, 

 either identical with, or closely related to, units of chemical capacity; 

 while kinetic and linear energy are not so related, except through the 

 periodic arrangement of the elements. 



It appears, therefore, to be a fundamental problem for the chemist 

 to ascertain, first, accurate atomic weights, and, second, to investigate 

 some anomalies which still present difficulties. In America, you have 

 excellent workers in the former branch. Mallet, Morley, Richards, and 

 many others have devoted their time and skill to perhaps the best 

 work of this kind which has been done; and F. W. Clarke has col- 

 lated all results and afforded incalculable help to all who work at or 

 are interested in the subject. Valuable criticisms, too, have been 

 made by Hinrichs; but it must be confessed that in spite of these, 

 which are perhaps the best determinations which have been made, 

 the problem becomes more, and not less, formidable. 



There are lines of work, however, which suggest themselves as pos- 



