the Constitution of Carbon Compounds, 109 



(31) While of opinion therefore that the arguments ad- 

 vanced by Thomsen, as a rule, do not suffice to substantiate 

 his views, I would yet express my conviction that even in 

 their present form his results are of the very greatest value, 

 and that it is already possible to base important theoretical 

 conclusions upon them. It may be doubted whether it will 

 ever be possible to determine the value of/. C, in the manner 

 he suggests ; but fortunately many of the problems of che- 

 mical affinity which press for solution may be solved without 

 the knowledge of this value by comparing isomeric compounds, 

 as in the case of the alcohols, for example §§ 10, 29 : and it is 

 in this direction that further investigation appears to be most 

 likely to lead to valuable results. 



It is before all things important, however, that independent 

 investigators should occupy themselves with thermochemical 

 studies, in order that the fundamental values may be placed 

 beyond doubt and that accurate thermochemical data may 

 be accumulated for discussion ; moreover, it is essential to 

 extend the field of study so as to include members of every 

 class of compound. 



XII. Note on the foregoing Communication. By Spencer 

 Umfreville Pickering, M.A., Professor of Chemistry at 

 Bedford College*. 



IN the foregoing communication Professor Armstrong 

 makes a suggestion which must recommend itself to 

 most chemists — that the heat evolved on the fixation of one 

 atom of oxygen by one atom of carbon is greater than that 

 evolved on the subsequent addition of a second oxygen atom 

 to the compound thus formed. The fundamental value,/. C 1; 

 on which all Thomsen's calculations are based, will thus be 

 erroneous; and the only meaning which can then be attached 

 to his values for i\, v 2 , and v 3 will be the differences between 

 their actual values. 



Thus, v 2 is given by the equation 



*=/- Ci- [(0 2 H 4 , 30 2 ) - (CH 4 , 20 2 ) ] 



=/.Ci- (333350- 211920); (I.) 



and i\ is deduced from the heat of formation of ethane, 



(2C,3H 2 ) = 6?< + Vl 



3(H 2 , ±00 + ~2f. C^CX |0 2 ) 



3 x 68360 + 2/. G ± - 370440= 6r + Vl ; . . (II.) 



* Communicated by the Author. 



