under the influence of Radium Bromide. 425 



in presence of various electrolytes, follows the law for a reaction 

 of the first order 



1 



t a — x 



Solutions of the pure dioxide, however, under the influence 

 of the platinum solution alone do not decompose strictly in 

 accordance with this law, the value of the constant increasing 

 as the concentration of the dioxide diminishes. 



It will be seen from the following results that solutions of the 

 pure dioxide, contained in paraffin-coated vessels, shew a similar 

 increase in the value of the constant as the decomposition pro- 

 ceeds, whether under the influence of radium rays or not. In 

 glass vessels the rate, which is at first irregular, appears to become 

 approximately constant after a few days. 



In both series, whether the solution is contained in glass or in 

 paraffin-coated vessels, the value of the constant for the decom- 

 position under the influence of radium appears, in each ex- 

 periment, to be approximately double of that in the parallel 

 blank experiment. 



The observations were carried out in the following manner : — 



The pure hydrogen dioxide was diluted to a convenient 

 strength with ordinary distilled water, and the solution accurately 

 titrated with potassium permanganate. This solution was then 

 divided into two similar flasks and kept in separate dark cupboards 

 in the same room, one of the flasks being placed directly over, 

 and almost in contact with, the specimen of radium bromide. 

 Equal portions (5 c.c.) were then withdrawn at stated intervals 

 and the strength determined as before by permanganate (0 - 0030 

 KMn0 4 per c.c). 



In the following table the concentrations (a — x) are expressed 

 in terms of the permanganate solution used and the time inter- 

 vals (t) in hours. Ordinary logarithms are used, so that 



K' = Kx 0-4343. 



I. Paraffin-coated flasks. 0*225 molar H 2 2 . 



Eadium Blank 



t (a-x) K' (a — x) K' 



... 



24 ... 



48 ... 



72 ... 



96 ... 



120 ... 



144 ... 



168 ... 



VOL. XII. PT. V. 28 



