i8 



CLARKE 



I2a -\- 6d — c — 8n 



= constant 



is properly applicable. Taking Thomsen's data we have the 

 following table : 



Mean, 13730 



Here the absolute heat of formation is still directly proportional 

 to the number of atomic linkings, all of the latter being equal 

 in value. 



In the alcohols the oxygen is wholly present as hydroxyl ; 

 that is, it is connected with carbon on one side and with hydro- 

 gen upon the other. With these compounds the usual for- 

 mula does not exactly hold, and a simple modification of it 

 becomes necessary. Let c represent the external oxygen 

 required for a combustion, and Cj the number of oxygen mole- 

 cules ^ contained in the alcohol, using quadrupled formulas as 

 heretofore. Then 



4^ 



—^7 — ' ^s- = constant, 



12a -\- 00 — C — C^ — Qfl 



at least for this particular series of substances. The data are 

 as given on next page. The results, on the whole, are satis- 

 factory, and their significance is evident when they are taken 

 in connection with previous series of computations. 



In the aldehydes and ketones all of the internal oxygen is 

 combined with carbon in the group = C = O ; but in the acids 

 of the paraffin series it plays a double part in the arrangement 

 O = C — O — H. Nevertheless these compounds, so far as 



'The word molecule as thus used is hardly exact. It is taken as equivalent to 

 a pair of atoms, and is so employed in order to avoid circumlocution. 



