NEW LAW IN THERMOCHEMISTRY 29 



amounts, and wouM produce its greatest effect in the higher 

 homologues of each series. 



Fourth. — Uncertainties in the corrections which have been 

 actually applied, and in the factors used in the computations. 

 For example, the uncertainties in the molecular weights of the 

 compounds, though very small, might amount in some cases to 

 two or three hundreds of calories. So also the reduction from 

 liquid to gaseous water is possibly too small, and hence the com- 

 puted value of the constant may be somewhat too high. 



Fifth. — In data and calculations of this kind there is always 

 a distinct possibility that essential physical corrections may have 

 been overlooked and neglected. 



Sixth. — In gasifying liquids of high boiling point, Thomsen 

 made use of his " universal burner." This leads to a suspicion, 

 which has often been voiced, that extraneous heat may have 

 been added to that due to the actual combustion. 



Seventh. — The average variation between lowest and highest 

 in Thomsen's detailed series of measurements is 0.45 percent. 



Taking all of these considerations into account, it seems clear 

 that the actual determinations of heat of combustion may well 

 be uncertain by as much as one per cent. In the last analysis, 

 however, averages cannot be trusted ; but each measurement 

 must be scrutinized separately, with reference to its own individ- 

 ual conditions and difficulties. It is probable, also, that the 

 mean value assigned to the henotherm is too high rather than 

 too low, and that its final value may be nearer to the usually 

 accepted value for the neutralization constant, namely, 13 700 

 calories. With the latter quantity we have already given esti- 

 mates of the heats of formation of several of the molecules which 

 fell outside of the regular organic series. With the new value, 

 13 777 calories, the absolute heats of formation of these mole- 

 cules, as deduced from the general formula, are as follows : 



