Certain Metals in Dissolved Iodine. 



211 



this paper ; 580 cc for the first reaction period, and 20 cc less for 

 each succeeding one. Values of c, the iodine concentration, 

 are expressed in cubic centimeters of an approximately 0*02 

 normal thiosulphate solution required by 20 ce of the liquid. 

 At is the time interval (t 2 — t i page 208) in minutes. A few 

 abnormal constants, indicated by parentheses, have been omit- 

 ted in calculating the averages. 



Table II shows the effect of varying acidity. Corrections 

 for fluctuations in the stirring have been applied by the 

 method described above, r being the mean rate of stirring 

 during the given reaction period. In experiments 4 to 11 the 

 correction data have been omitted for the sake of brevity, 

 but the average given in each case is that of the corrected 

 constants. 



A necessary readjustment of the apparatus between this 

 series and that of Table I has slightly altered the value of the 

 constant. A proper comparison is obtained by comparing 

 experiments 2, 3, and 4, which are closely concordant, and 

 whose average is Iv = 6'86, with the 6-72 of Table I. 



The close agreement between the first five experiments of 

 Table II shows that a change in acidity between the limits of 

 O002 and 0-1 normal has no appreciable effect upon the results. 

 Further increase in the acidity diminishes the rate of solution 

 by an amount which increases with the concentration of the 

 acid. A comparison of experiments 3 and 4 shows that the 

 substitution of hydrochloric for sulphuric acid does not appre- 

 ciably alter the constant.* A similar agreement between 

 the effect of hydriodic acid and of sulphuric acid at 0'5 

 normal concentration will appear later. 



H 2 S0 4 



v = 

 At= 

 o 

 K = 



r = 



Metal : Cadmium. 

 0-002 normal. 

 580 560 



10 10 



Table II. 

 KI 0'5 normal. 



= 1965 



17-51 



Temperature 25°. 



540 520 500 480 460 



10 10 10 10 10 



15-50 13-61 lost 10-41 9-05 780 



6-68 

 170-5 



K (corr.) = 6-67 



6-83 

 170-0 

 6-83 



6-78 

 169-3 

 6-80 



169-5 



6-83 

 171-1 



6-82 



6-72 

 168-9 

 6-75 



6-82 

 169-5 

 6-84 

 Av. 679 



I. H 2 S0 4 0-02 normal. 



Af= 10 10 10 10 10 10 



c = 19-92 17-71 15-68 13-74 12-09 10-51 9'09 



K= 6-82 6-81 7-12 6-65 6-99 6-96 



r = 171-3 170-1 171-0 170-2 1709 168-8 



K (corr.) = 6-78 6-81 7"09 6-64 6-96 7'00 Av. 688 



* Compare also, in Table III, experiments 1 and 2, and in Table VI, 

 experiments 8 and 9. 



