348 M. H. Kolbe on the Province of Mineral Chemistry. 



tion of temperature, which was that which was due solely to the 

 remainder of the heat after this portion had been separated 

 from it. 



It appears, therefore, that a conclusion, legitimately deduced 

 from a certain experiment, has been too hastily generalized, and 

 is now enunciated as true in all cases, beyond the limitations 

 which, though not observed, were nevertheless present at, and 

 controlled the results of the original experiment. It is true that 

 as often as gas is condensed or rarefied under an invariable pres- 

 sure, there will be a change of temperature representing a gain 

 or loss of heat proportionate to pdv. But when the pressure is not 

 constant, the variation of temperature will be proportional to 

 d(pv), and not to pdv. d(pv) may be nothing; pdv may be 

 = — vdp. In that case there is no variation of temperature ; 

 and in all cases where d(pv) has any value different from nothing 

 and different from pdv, there will be a change of temperature 

 which does not represent a quantity of heat proportional to pdv. 



In a short paper upon this subject, published in the April 

 Number of this Magazine, I attempted to represent the same 

 argument (adopting the language and conceptions of the new 

 philosophy itself) as I am now urging in the older and more 

 generally familiar modes of expression. I believe that^z; is the 

 true expression for the maximum internal potential energy, vdp 

 is the elementary potential energy expended, and pdv is the 

 elementary work done. So long as pdv + vdp = 0, the internal 

 forces, or potential energy, do all the internal work that is 

 done, and no other, and d(pv) or Bcft=0, and there is no change 

 of temperature. When pdv + vdp has a value, positive or nega- 

 tive, i. e. when pdv is > or < vdp, then, and then only, is the 

 temperature affected. 



Milland, Lipkook, April 18, 1870. 



LI. The Province of Mineral Chemistry. 

 By Hermann Kolbe*. 



ORGANIC chemistry, once the neglected sister of the maturer 

 inorganic chemistry, has become so honoured and courted 

 since Liebig introduced her as a young science into the chemical 

 world, that her relative has gradually been thrown into the shade. 

 But now we are beginning to see that inorganic chemistry is not 

 deserving of this neglect, but that in her lap she hides a store 

 of undiscovered treasure — the promised reward of those who 

 cherish her. 



* From the Journal fur Praktische Chemie, neue Folge, vol. i. p. 1. Trans- 

 lated by Dr. T. E. Thorpe, Owens College. 



