PRESENT I'KOHLKMS OF INOKOANK; CHEMIHTRY. 209 



such that the surfaoe eiun-ofy for equal numbers of molecules distrib- 

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

 the temperature at which surface enerjjy is zero — that is, the critical 

 point. This ijives a means of determining; the molecular weights of 

 liquids, and we assume that the moleculai" weij>:ht of a compound is 

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

 •2. I'he 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- 

 poi-tional to their atomic weights, and of compounds to the quotient 

 of theii- 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 

 reciprocal 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 Ave 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 l)y a simple factor with equivalent, electric potential is 

 proportional 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 investi- 

 gate some anomalies which still present difficulties. In America you 

 iiave excellent workers in the former branch. Mallet, Morley, 

 Ivichards, and many others have devoted their time and skill to per- 

 iiaps the best work of this kind which has been done, and F. W. 

 (.'larke has collated all results and afforded incalculable help to all 

 who work at or are interested in the subject. Valuable criticisms, 

 too, have been made by Tlinrichs; but it must be confessed that, in 

 spite of these, which are [)erliaps 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- 

 sibh' likely to throw light on the (|uesti()n. P'irst, there is a striking 

 anomaly in the atomic weight of nitrogen, determined by analysis 

 SM 1904 14 



