368 G. A. Linhart — Reduction of Mercuric Chloride. 



5. When hydrochloric acid is present at the outset the veloc- 

 ity coefficient, calculated for a reaction of the second order, 

 shows a steady increase to two or three times its initial value. 

 This, however, is what would be expected, on account of the 

 breaking down of the complexes with decreasing concentration, 

 upon the assumption that only the single molecules of HHgC] 3 

 react with phosphorous acid. 



6. Fairly concordant velocity constants are obtained if, in 

 the velocity equation (5), (a — x) is replaced by m{a—x), where 

 m denotes that fraction of the total mercuric chloride present, 

 at any time t, which is in the form of single molecules 

 (HHgCl 3 ), whose concentration is assumed to be always small 

 in comparison with that of the double molecules, H 3 Hg 2 Cl 6 . 



