INFLUENCED BY RADIUM. CREIGHTON. 39 



In the preceding table column five gives the changes in pres- 

 sure of the gas in millimetres of mercury. These values have 

 been calculated from the data in column four, the hydrogen 

 peroxide having a density which is approximately one. Column 

 six contains the values of colum'n five after approximate cor- 

 rections have been made for the changes due to variation in 

 temperature and pressure ; that is, these numbers represent the 

 changes in pressure due to the increase of gas. 



From these results, then, it is seen that the effect of radium 

 on the solution of hydrogen peroxide is to decompose it. This 

 decomposition, however, is small; for the increase in pressure 

 corresponds only to a small increase in volume. In its behaviour 

 towards hydrogen peroxide radium resembles light. It will be 

 noticed that the pressure exerted by the gas, as given in the 

 sixth column of the above table, after a time begins to decrease. 

 The reason of this diminution in pressure will be considered 

 later. 



It is a well-known fact that the presence of finely divided 

 solid matter or salts of the heavy metals slowly decomposes con- 

 centrated solutions of hydrogen peroxide, even at ordinary 

 temperature. For this reason 10 cc. of ^ solution of lead 

 nitrate were added to 350 cc. of the dilute hydrogen peroxide 

 'used in these experiments. The addition of the lead nitrate to 

 the peroxide caused the formation of a finely divided precip- 

 itate, the presence of which should also tend to decompose the 

 solution. After making the necessary approximate corrections 

 for changes in temperature and pressure, it was found that 

 during the ten days the solution was under observation the pres- 

 sure had not changed at all. Hence, it would seem that dilute 

 solutions of hydrogen peroxide are not, or at most only exceed- 

 ingly slowly, decomposed by the presence of finely divided solid 

 matter or solution of lead nitrate. 



A'n experiment similar to this was next carried out, with 



