4 THE INFLUENCE OF RADIUM ON THE 



containing the radium was held in the end of a hollow brass 

 rod, which was placed in a fixed position in a wooden block; 

 this latter fitted into the mouth of one of the bottles Thus, by 

 filling the bottle to a definite mark, the distance between the 

 radium and the surface of the liquid was always kept the same. 

 This distance was between two and three millimeters. 



These experiments were all carried out in a photographic 

 dark room, so that there was no chance of the reaction being 

 influenced by light. The solution which was not to be acted on 

 by radium was protected from the rays by a screen of lead, so 

 placed that the solution would not be affected appreciably by 

 the secondary rays set up in the lead. 



(Several experiments carried out in this way showed, at the 

 end. of twenty- four hours, that the decomposition in the solution 

 acted upon by radium was greater than the decomposition in 

 the other; but the excess varied in different trials from 15 per 

 cent to 25 per cent. In order to obtain more concordant 

 results for similar experiments, the temperature at which the 

 reaction took place was kept constant for a series of measure- 

 ments and it was found that this made a decided improvement 

 in the agreement of the results. It was still found, however, 

 that the differences in results under similar conditions were 

 considerably greater than those due to experimental error. In 

 'order to see whether these differences were due to small errors 

 in the mixing of the solutions, a large quantity of solution was 

 prepared and divided into six equal parts of 225 cc. each. These 

 were allowed to stand for twenty hours in the dark room, with- 

 out radium, at a temperature of 16 0.5C. At the end of 

 that time the amount of decomposition, as measured by the 

 number of cc. of titrating solution required, was found to be for 

 the several- portions, 5.38, 5.23, 5.41, 5.34, 5.07, 5.33, respectively. 

 The lack of equality of these numbers shows that the irregular- 

 ity is not to be accounted for in this way. 



The influence of the impurities in the ordinary distilled 

 water used in making up the solution was next investigated, 



