28 THE ROYAL SOCIETY OF CANADA 



Boltwood standard consisted of 3-51 instead of 3-69 milligrams of 

 radium bromide. It is therefore 4-9% low on the International. 

 It is known that radium bromide on exposure to air gives up bromine, 

 and changes over to the carbonate, while water of crystallisation 

 is also formed. This is suggested by Sir Ernest Rutherford as an 

 explanation of the increase of weight. 



(b). — Solution Standards. 



For laboratory purposes a solution standard is prepared. This 

 is obtained by comparing a small quantity of the radium salt with a 

 solid standard by the /-ray method. It is then dissolved in distilled 

 water with a little HCi, to keep it in solution. 



Such a solution, but with no acid added, was made up by Eve at 

 about the same time as the preparation of the Rutherford-Boltwood 

 folid standard, using about one quarter of a milligram of radium 

 bromide. Determinations by Boltwood a few years later at New 

 Haven with some of this solution led to results which conflicted with 

 those obtained by Eve in similar work, where the solid standard 

 was used. It was shown by the latter that the original solution had 

 weakened by the deposit of radium on the walls of the flask, as no 

 hydrochloric acid had been used in the preparation. Two new 

 solutions were then prepared by Boltwood from a known amount of 

 radium bromide, determined by Eve by the /-ray method. These 

 solutions were of strength in the ratio of 100: 1, one containing 1 -57 X 

 10"^ and the other 1 -57X10"^ gram of radium per c.c. This time 

 a little HCI was added as a precaution, to keep the radium in solution. 



Since the Rutherford-Boltwood solid standard is known to be 

 4-9% low on the International, and the Rutherford-Boltwood solu- 

 tion standards were compared with the former, considerable import- 

 ance attaches to finding whether its accepted value may not also be 

 in error, and to what extent. The more so, since determinations by 

 Boltwood on the relative amounts of uranium and radium in rocks, 

 and results obtained by Eve and others for the amount of emanation 

 in air, and also of radium in rocks and water, are based upon these 

 solution standards at their present accepted value. The investigation 

 was carried out by comparing the weak solution of the Rutherford- 

 Boltwood standard with a solution of the Washington standard. 

 A litre of the latter was obtained by Eve in September, 1914, from 

 Satterly of Toronto University, containing 9-15X10"^^ grams of 

 the radium element per c.c. It was certified as follows: 



"100 c.c. of acid solution of the Washington Standard of strength 

 12-2X10"^ gram of radium per c.c. 10 c.c. of this were diluted 

 to one litre. 250 c.c. of this were removed, and distilled water added 



