Chemical Affinity. 



189 



The authors also consider the special case in which A = ferric 

 chloride, B= hydrochloric acid, Aj = ferric oxide, and B x = 

 water; and also that in which A = nitric acid, B = sodium 

 nitrate, A! = sulphuric acid, and Bj = sodium sulphate. The 

 experimental data for the first case were accumulated by G. 

 Wiedemann (Pogg. Ann. 1878), and those for the second case 

 are taken from the researches of Thomsen. 



It is evident from equation (1) that the proportion k x : k is 

 determined by experiment, but not the actual value of k x and 

 1c. By carrying out analogous experiments with new systems 

 A, B, A 2 , B 2 , &c, it is easy to determine the new proportion 

 k 2 &c. : k. If, now, k be taken as = 1, the relative values of 

 kiy k 2 , &c. are obtained in reference to the pair AB. A Table 

 may be thus drawn up by the aid of which the conditions of 

 equilibrium for those systems which any two pairs of bodies 

 in the Table are capable of forming among themselves may be 

 calculated. 



Thus, if it be wished to calculate the conditions of equilibrium 

 for the system A 1? A 2 , B 17 B 2 , the equation is 



Pl- 



h^=k 



P2. 

 Q2 



and the values of k x and k 2 are found from the Table. 



The three following Tables have been drawn up from data 

 taken from Thomsen's researches. 



A. 



Hydrochloric acid. 

 Nitric acid. 

 Sulphuric acid. 

 Oxalic acid. 

 Phosphoric acid. 

 Tartaric acid. 

 Citric acid. 

 Acetic acid. 

 Boric acid. 



Table I. 

 Relative values of k. 



HC1 



HN0 3 



i(H 8 S0 4 ) 



i(H 2 C 2 4 ) 



H 3 P0 4 



i(C 4 H 6 6 ) 



i(O e H 8 7 ) 



C 2 H 4 2 



HB0 2 



K 



NaCl 



NaN0 3 



i(Na 3 S0 4 ) 



i(Na 2 C 2 4 ) 



KaH 2 P0 4 



i(C 4 H 4 Na 2 6 ) 



i(C 6 H fi Na 8 7 ) 



C 2 H 8 Na0 8 



NaB0 2 



k. 



1 



1 



0-25 



0-0676 



0-0625 



0-0025 



0-0025 



0-0009 



0-0001 



Table II. 



A. B. k. 



Hydrochloric acid. Metallic chloride. 1 



Sulphuric acid. Metallic sulphate. 0'25 



The metal may be potassium, sodium, or ammonium. 



