Section III., 1915 [27] Trans. R.S.C. 



A Comparison of Radium Standard Solutions 

 By J. MoRAN, B.Sc, McGill University. 

 Presented by Dr. A. S. Eve, F. R.S.C. 



(Read May Meeting, 1915). 

 SECTION 1. HISTORY. (a). SOLID STANDARDS. 



The fundamental Radium Standard of the present time is the 

 International Radium Standard at Sèvres, France. It was prepared 

 by Mme. Curie in 1912, on the recommendation of the Congress of 

 Radiology and Electricity which met at Brussels in 1910.^ It con- 

 sists of 21-99 milligrams of pure radium chloride, sealed up in a thin 

 glass tube. This standard, before being accepted, was compared 

 with three other purified amounts of radium chloride, prepared 

 by Honigschmidt for atomic weight determinations. These all agreed 

 with Mme. Curie's standard to within one part in three hundred. 

 One of Honigschmidt's preparations has been preserved at the Radium 

 Institute of Vienna, as a secondary standard, and termed the Vienna 

 Standard. 



Before this, however, in 1903, the first radium standard was 

 prepared at McGill University, Montreal, and termed the Ruther- 

 ford-Boltwood Standard. A quantity of pure radium bromide was 

 bought from Dr. Giesel of Germany, and generously presented 

 to McGill University by Sir William Macdonald. Of this amount, 

 3 • 69 milligrams were weighed out and sealed up in a tube by Professor 

 Eve and Dr. Levin, and thereafter constituted a primary laboratory 

 standard. It is now at Manchester University, England. 



Various secondary national standards exist, examples of which 

 are the English standard at the National Physical Laboratory, 

 and the Washington standard in U .S.A. These have all been accurately 

 compared with the International and Vienna standards. 



After the preparation of the International standard, the Ruther- 

 ford-Boltwood standard was carefully compared with it, and also 

 with the Vienna standard. It was compared indirectly with these 

 by means of the secondary standard at the National Physical 

 Laboratory. These investigations showed that the Rutherford- 



1 "Radioactive Substances and their Radiations," 1913 ed. By Sir Ernest 

 Rutherford. See also Phil. Mag. Sept., 1914. Sir E. Rutherford. 



