Affinity and Dissected {Structural) Formula, 415 



22. It may be noticed that the values of H 100 can also be cal- 

 culated from the equation 



H 100 =S{2S(H 1 + H 2 )^-S{28(H 1 + H 2 )^ 



where 2 {^{^i + H 2 ) \ m and 2 {28 (H x + H 2 ) }^ indicate the alge- 

 braic sums of the values of 2S(H X 4- H a ) for the materials and pro- 

 ducts respectively ; for these quantities indicate respectively the 

 heat that would be generated were the materials in the gaseous 

 state at 100° and 760 millims. burnt to gaseous carbon dioxide and 

 liquid water at 15° and 760 millims., and that absorbed were the 

 resulting carbon dioxide and liquid water at 15° and 760 mil- 

 lims. converted into the gaseous products at 100° and 760 

 millims. It is easily seen on examination that this equation can 

 be inferred from the previous one involving H 100 , and the fun- 

 damental equation involving 2o\F 100 , from which the numbers in 

 the Table are calculated. 



23. If it be required to know the heat-disturbance during any 

 reaction when the materials and products are measured under 

 circumstances different from those above stated (vaporous state 

 at 100° and 760 millims.), this can easily be calculated by means 

 of the formula 



where %(h x ) m and 2(AJ represent the algebraic sums of the 

 amounts of heat absorbed in the alteration of the materials and 

 products respectively to the new conditions. H^ thus becomes 



=2{2S(H 1 + H 2 )+y m -2{2S(H 1 + H 2 )+/*4 p . 



Thus, if ethylic alcohol in the liquid state at 15° give rise to 

 ethylene and liquid water measured at 15° and 760 millims., the 

 value of H^ becomes 



H, = S(2SH 1 ) ro -2(2SH 1 ) p) 



as 



2(2SH 2 )„ = -2 ( y ra) 



and 



2(28H 2 ) p = -2(/y ? , 



or 



H, = 46x 6-998- (28x11-919 + 18x0) = -11-8. 



24. By reversing this mode of calculation, it becomes possible 

 to infer from the heat-disturbance taking place in any given re- 

 action under known conditions the heat-disturbance that would 

 take place under the conditions taken as standard (vaporous 

 state at 100° and 760 millims.), and hence to infer the differ- 

 ences between the algebraic sums of 2 (F p ) and S(F OT ) , or, in other 

 words, to obtain the means of correcting the first approximations 



