248 Van Name and Edgar — Velocities of Certain Reactions 



while the concentrations directly indicated by the titrations 

 are given under C. It will be observed that each C denotes 

 the concentration of the bromine at the beginning of a time 

 interval At, the concentration at the end of the same interval 

 being that value of C which is found in the table on the 

 horizontal line next below, so that the equation by w T hich the 

 constant K" is calculated takes here the form 



" v C ' 

 At C 2 

 The analyses, both here and in the later experiments with 

 mercury, were made by running each sample from the pipette 

 into an excess of potassium iodide solution and titrating the 

 iodine in the usual way. 



From the mean values of K" in the three experiments of 

 Table VI the following values were obtained by graphic 

 interpolation : 





Table VII. 





V 



K" 



for At - 



480 



4*55 





460 



4-70 



0-0044 



440 



4-84 



0048 



420 



4-96 



0-0051 



400 



5-06 



00055 



380 



5-15 



0-0059 



In the experiments with mercury and bromine the same 

 method was followed as in those with iodine, but with atten- 

 tion to certain details which were previously not important. 

 The pipette was tilled immediately after each removal of the 

 disk from the solution, and the time during which the disk 

 remained out of the liquid was limited to exactly one minute in 

 each case. The concentration changes due to loss of bromine 

 during each such interval were calculated with the aid of the 



0' 



above values of log-W-- Table VIII contains the results of 



two parallel experiments on the rate of solution of mercury in 

 bromine, with the necessary corrections applied. Under c 

 are the bromine concentrations as determined by direct analysis, 

 under c' the (calculated) concentrations at the moment of 

 inserting the disk. The concentrations at the beginning and 

 end of the same reaction period At are therefore given respec- 

 tively by c' and that value of c which stands on the next line 

 below. K7 is the combined velocity constant for the solution of 

 mercury and the evaporation of bromine. K is the velocity 

 constant for the solution of mercury alone, obtained by sub- 

 tracting from E7 the corresponding value of K", as given in 

 Table VII. 



