38 Mr. W. Sutherland on the Fundamental 



C (diamond) + H + 3C1 = CHC1 3 (gas) + 35*9, 

 C(diamond) + 4C1 = CCl 4 (gas) 4- 47. 



The differences in both cases ought to be the same ; with 

 Thomsen' s data it is +3*1, whereas with Berthelot and 

 Matignon's it is — 11*1. It is quite clear that none of 

 Thorn sen's exceptional results for the haloid compounds can 

 be accepted under such conditions of experimental uncertainty, 

 nor can we attach much weight to his values 13*4 for the 

 heat evolved on the junction of an atom of CI to an atom of 

 C, 5*9 for Br and C, and for I and C —5*9. These are 

 values of our/(CCl),/(CBr), and /(CI), and it would be of 

 great interest to ascertain whether/ (CI) really has a negative 

 value : but all the essential points in the thermochemistry of 

 the organic haloid compounds have still to be cleared up by 

 some experimenter who can devise such means of control of 

 his experimental results as will enable him to assign limits of 

 error within which his results must lie. Berthelot and 

 Matignon claim for their results for six chlorine compounds 

 (Compt. Bend, cxii.) by means of explosion with compressed 

 oxygen in presence of a sufficiency of combined hydrogen 

 and solution of arsenious acid to prevent the formation of free 

 chlorine, that they are the most accurate yet obtained for 

 chlorine compounds with organic radicals. Berthelot (A?in. 

 de Ch. et de Ph. 6th ser. xxviii.) finds for the evolution of heat 

 when CI acting on CH 4 liberates 1, 2, 3, or 4 atoms of H, the 

 following values, 10*3, 2 x 7*1, 3 x 9'3, and 4 x 12*5, whereas, 

 according to Thomsen, these values must be all nearly zero ; 

 this shows that we can attach but little weight to Thomsen's 

 negative value for /(CI), and once more proves what an 

 excellent field for the experimental thermochemist the haloid 

 organic compounds still remain. 



3. The Alcohols. — The most important result is that the 

 differences of the heats of formation of the primary alcohols 

 and of the related paraffins are constant ; that is that the heat 

 of formation of the radical OH from gaseous oxygen and 

 hydrogen and its substitution for an atom of H in a paraffin 

 is constant, or, according to our notation, 



(0)+/(OH)+/(C-0)-/(OH) 



is constant, the average value of the constant, according to 

 Thomsen, being 29*5 ; and as/(CH) is 15, and (0) and (H) 

 are both zero, then 



/(OH)+/(C-0)=44-5 (27) 



