2 Rutherford and Boltwood — Radium and Uranium, 



10~ 6 milligram of radium bromide per cubic centimeter. By 

 evaporating known quantities of these solutions and testing 

 the a-ray activity of the residues, Eve found that the relative 

 activities were in close agreement with their supposed content 

 of radium. There was, therefore, every reason to assume that 

 the standard solutions were correct. About two months after 

 preparation, a portion of one of these solutions was trans- 

 ferred to another bottle and sent to Boltwood, who, assuming 

 the accuracy of the standard, determined by experiment that 

 the amount of radium corresponding to one gram of uranium 

 in a mineral was 7'4XlO -7 gram. 



Recently, however, some experiments made by Mr. Eve in 

 the laboratory of McG-ill University indicated that the solu- 

 tion used for the above determination was in some way defec- 

 tive and that the quantity of radium actually in solution was 

 less than had been assumed to be present. It was found that 

 a considerable proportion of the radium had been deposited 

 on the surface of the glass vessel in which the solution had 

 been preserved and it is probable that this action had taken 

 place before the solution sent to Boltwood was withdrawn. 

 A full account of Mr. Eve's experiments is given by him in a 

 paper which accompanies this in the same number of the 

 Journal. We desire to thank Mr. Eve for his kindness in 

 drawing our attention to this matter and for his assistance in 

 preparing a new radium standard. 



The method employed for determining the quantity of 

 radium present in the material from which this new standard 

 solution was prepared is described in detail in Mr. Eve's 

 paper. The weight of radium bromide taken was ascertained 

 by this method to be equal to 0'27 milligram. The minute 

 fragment of salt was removed from the small sealed vial in 

 which it had been received and was dropped into a small 

 beaker containing a few cubic centimeters of dilute hydro- 

 chloric acid. The liquid was heated and was then carefully 

 examined with a glass, when absolutely no trace of any insolu- 

 ble material could be detected. The vial which had contained 

 the salt was washed several times with concentrated hydro- 

 chloric acid and water, and these washings were added to the 

 main solution. The solution was introduced into a standard 

 graduated flask, the volume was increased to exactly 1000 cc by 

 the addition of freshly distilled water, and the whole was 

 agitated for some time in order to insure complete mixing. 

 Ten cubic centimeters of this solution were now withdrawn 

 with a standard pipette and introduced into a second gradu- 

 ated flask. A few cubic centimeters of dilute hydrochloric 

 acid were added and the solution was diluted to 1000 cc with 

 distilled water. After thorough mixing, 10 cc of this second 



