ABSTRACT
Radium has consequently been possible to compare the standards in use for many years in the Laboratories in Montreal and Manchester with the International Standard. It may be of interest to mention briefly the history of the preparation which for ten years has served as a laboratory standard and in terms of which a number of important radioactive magnitudes have been measured. The result was expressed in terms of the 3.69 milligram standard, which has generally been referred to as the 'Rutherford-Boltwood' standard. A radium standard in use in the Laboratory in Manchester was accurately compared for me by Professor Stefan Meyer, Secretary of the International Radium Committee, in terms of the Vienna standard, which has been set aside as a secondary International standard. It has been suggested to me that it would be a convenience to many workers if the various radioactive magnitudes determined in the Laboratory at Manchester were re-calculated in terms of the International Standard.
