The end of the 19th century was the era of the invisible ray! From cathode rays, to ultraviolet rays, to X-rays, there was a ray to suit every taste. In February 1896, the French physicist Henri Becquerel noted that uranium salts could expose photographic plates without needing to be "charged" by exposure to the sun.
Henri Becquerel in his laboratory (circa 1903) by Source : Musée Curie (coll. ACJC)Musée Curie
It appeared that uranium spontaneously generated a type of energy in the form of invisible rays, called "uranium rays" or "Becquerel rays."
From Uranium Rays to Radioactivity
In 1898, Marie and Pierre Curie developed an experimental method for quantitatively and accurately measuring uranium radiation. This method was to play a crucial role in the history of radioactivity...
The hangar of Pierre and Marie Curie (1898) by Source : Musée Curie (coll. ACJC)Musée Curie
At the end of 1897, Marie Curie was working in a window-lined workshop at the Paris School of Industrial Physics and Chemistry. Her focus was uranium rays, a phenomenon that was still unexplained and hadn't been studied much by the scientific community. Rather than seeking to understand the nature of the rays, Marie Curie's objective was to verify whether or not they were specific to uranium.
With Pierre Curie, she developed a method that allowed her to quantitatively measure the emission of a given radioactive source. This method measured the electricity generated by the rays, which is proportional to the radioactive emission.
Piezo-electric quartz (1920) by Source : Musée Curie (coll. Institut du radium)Musée Curie
The unique feature of the Curie method is the piezoelectric quartz, an instrument developed by Pierre Curie and his brother Jacques in the 1880s. As a standard for measuring electric charge, it improved the accuracy of the measurements obtained by the Curies based on very low quantities of electricity.
Pierre and Marie Curie ; caricature published in "Vanity Fair" in 1904 (1904) by IMP. Source : Musée Curie (coll. ACJC)Musée Curie
Thanks to the Curie method, Marie and Pierre Curie were soon able to demonstrate that other minerals emit the same type of invisible rays as uranium. They discovered two new elements: polonium and radium.
The Curie Method during the 20th Century
The Curie method was used for measuring radioactivity in the Curie laboratory for several decades before being gradually replaced from the 1930s.
Stefania Maracineanu in the first floor physics room of the Curie laboratory (1922) by Albert Harlingue. Source : Musée Curie (coll. ACJC)Musée Curie
In 1921, the Curie laboratory in the Radium Institute contained no less than 12 measuring tables equipped with this apparatus.
Galabert and Regnier in one of the measurement rooms of the Curie laboratory (1930) by Source : Musée Curie (coll. ACJC)Musée Curie
The measurement of radioactivity using the Curie method required a certain dexterity. Everyone who passed through the Curie laboratory soon learned this.
To measure radioactivity : the Curie method (2016) by Uriel ChantraineMusée Curie
A set of the instruments that were used for measuring radioactivity in the Curie laboratory has been restored to full functionality and can now be found at the Curie Museum— in the same spot where Marie Curie once carried out her own radioactivity measurements.
Conception : Musée Curie