G. A. Linhart — Reduction of Mercuric Chloride. 353 



Art. XXXII. — On the Rate of the Reduction of Mercuric 

 Chloride by Phosphorous Acid ; by G. A. Linhart. 



[Contributions from the Kent Chemical Laboratory of Yale Univ. — ccxliii.] 



In 1902 Montemartini and Edigi,* in studying the velocity 

 of the reaction between phosphorous acid and mercuric chloride, 

 represented it by the following equation : 



2HgCl 2 + H 3 P0 3 + H,0 = 2HgCl + H 3 P0 4 + 2HC1, 



and considered it, therefore, to be a reaction of the third order, 

 since the concentration of the water may be considered practi- 

 cally constant under the conditions of the experiment. How- 

 ever, these investigators were unable to obtain concordant 

 figures for the velocity constants when substituting their exper- 

 imental results in the formula, 



K=-L * 



2t \(c-aj) f c 2 / 



They then substituted their experimental results in a formula 

 representing a reaction of the second order, but again failed to 

 obtain constant figures. This abnormal behavior of the reac- 

 tion between mercuric chloride and phosphorous acid they 

 attributed to the effect of some initial disturbance. 

 j£5 Garner, f Foglesong and Wilson consider the reaction to be 

 of the fourth order, although they represent it by the same 

 equation as given above. They draw this conclusion not from 

 any theoretical consideration, but because " values for the second 

 and third order equations decrease rapidly, and those of the 

 fourth order are reasonably constant." In the calculation of 

 the velocity constants these investigators employ the formula, 



K= l ' ' 



3t \(a—xY a* 



which applies only to the special case where the concen- 

 trations of the reacting substances are all equal, but they use 

 it even in cases when the concentrations of the reacting sub- 

 stances in their experiments are unequal. In a later number of 

 the same Journal^, however, Garner acknowledges the error in 

 this procedure and states that his results will be recalculated 

 and published in a subsequent paper. However, the recalcu- 

 lated results have not yet appeared in print. 



*Gazz. Chim. Ital., xxxii, 2, p. 182. 



t Amer. Chem. J., xvi, 361. % Ibid., p. 648. 



Am. Jour. Sci.— Fourth Series, Vol. XXXV, No. 208. — April, 1913. 

 25 



