RICHARDS AND ARCHIBALD. — CONCENTRATED SOLUTIONS. 357 



less and less satisfactorily with the facts, the amount of mercury actually 

 found always exceeding the calculated amount. Evidently this disagree- 

 ment may be due to the fact that some of the new complex acid remains 

 in the uudissociated state; the calculation considers only the ion, while 

 the mercury weighed in analysis constituted the sum total. The exact 

 calculation of the amount undissociated is impossible for two reasons; 

 in the first place, the mode of dissociation of such a tri-ionic comjxmnd as 

 H 2 HgCl 4 is uncertain ; and in the next place, we have no data for the 

 extent of the dissociation of the compound beyond the strength of a nor- 

 mal solution. • 



In spite of this double uncertainty, it is possible to make an approxi- 

 mate calculation. This is sufficient to show that in a general way the 

 argument is sound. The approximate calculation is based upon the fact 

 that so far as the extent of dissociation of the complex acid is known, it 

 is equal to that of hydrochloric acid at the same concentration.* On mak- 

 ing the assumption that this relation holds in very strong as well as in 

 moderately strong solutions, and waiving entirely the uncertainty as to the 

 possible existence of the half-way ion HHgCl 4 ', the proportion of the 



Approximate Calculation of the Total Amount of Mercury. 



* Le Blanc and Noyes, loc. cit. 



t These figures were obtained by graphic interpolation from the figures of 

 Kohlrausch and Holborn, Leitvermogen U. Eiectrol., p. 154 (1898). 

 \ By interpolation. 



