Atomic Laws of Thermochemistry. 3e> 



molecules ; in our notation we have 



4(H) +4/(CH) + (C solid) =21-2, 



-(C solid) =38-4; 



.-. 4(H) + 4/(CH) =59-6. ... (10) 

 ! Or, strictly, 



4(H) +4/(CH) +/(00 3 )-2/(00)=59-6. 



As H 2 is a diatomic molecule it may be that (H) = 

 similarly to the cases of CI, Br, and I, and then equation (10) 

 becomes 



4/(CH) = 59-6 (11) 



The case of C 2 H 4 ought to work out to practically the same 

 result as that of CH 4 ; following Thomsen we will take it as 

 another example : — 



2(C solid) + 4(H) +/(C:C)+4/(CH)= -3-3, . (12) 



-2(0 solid) +/(C0 3 ) -2/(00) = 76-8, 



and by (7) 



/(0:C)+/(00 3 )-2/(CO) = 14-2. 



Therefore adding the first two equations and subtracting the 

 third, 



4(H) + 4/(0H)= 59-3. 



8. Fundamental Thermochemical Constants. — From all his 

 data for the hydrocarbons Thomsen determines average values 

 of his constants v l9 v 2 , and v s , the thermal values of single, 

 double, and treble bindings of carbon atoms, and for r the heat 

 developed when an atom of hydrogen is forced out of a mole- 

 cule of hydrogen and united to an isolated atom of carbon ; 

 he gets a series of equations, such as 



for CH 4 



59-6 = ±r, 



for C 2 H 6 



104-2 = 6r + ^, 



for C 3 H 8 



148*5 = 8r + 2^, 



and so on, for 6 paraffins in all. Applying the method of least 

 squares to ihe six equations for two unknowns he finds 

 2r=30'l and v 1 =14*0, which is nearly the same as the 

 value already found for v 2) namely 14*2. 



To find v 3 h& uses the data for acetylene 2 H 2 , allylene 

 C 3 H 4 , and dipropargyl C 6 H 6 , which give the equations : — 



Phil. Mag. S. 5. Vol. 40. No. 242. July 1895. D 



