Marie Curie, who would soon receive a second Nobel prize, this time for chemistry, had strong ideas about the directions to take towards international standards. The first order of business of this committee was to agree to the quantity and unit for radioactivity. It was quickly agreed that the unit for radioactivity would be the Curie in memory of Pierre Curie, but there was considerable discussion over the amount of activity that would correspond to 1 Curie. (A working amount of radium at the time was of the order of a few milligrams of the element.) Marie Curie felt that it was inappropriate to use the name Curie for an infinitesimal amount of material, so she insisted that a Curie correspond to a larger amount. Her definition was "la quantité d'émanation en équilibre avec un gramme de radium." That is, that quantity of 222Rn (3.8 day half life) in equilibrium with one gram of its parent 226Ra.
The second order of business for the committee was to agree on an international standard that could be used to intercompare radium preparations from the principal laboratories in North America, UK, France, Germany and Austria. The preparation of a radium standard was assigned to Marie Curie, and in 1911 she prepared 21.99 milligrams of pure radium chloride in a sealed glass tube. The job of preparing multiple standards for distribution fell to a chemist, Otto Hönigschmid in Vienna, who was expert in gravimetric measurements and a leading authority on measurements of atomic weights.
"The International Committee on Radium Standards also arranged for the preparation of standards for those governments that required them. These secondary standards are compared directly both with the International Standard in Paris and with the Vienna Standard. In December, 1913, the United States received its standard. It is designated by the Committee as 'Secondary Radium Standard No. 6,' and is certified to have contained in the autumn of 1913, 20.28 mg. of radium chloride, equivalent to 15.40 mg. of radium. This radium standard is preserved at the National Bureau of Standards at Washington, D.C., and is the primary radium standard of the United States. The radium content of all the working standards at the Bureau are determined by comparison with this. The certificate was signed by Stefan Meyer from the Institut für Radiumforschung in Vienna, Marie Curie and Ernest Rutherford. The certificate has three columns and the text is replicated in German, French and English. The radium in this standard had been obtained from pitchblende from St. Joachimstal in Bohemia."