Cartoon from Vanity Fair of Marie and Pierre Curie.

Marie Curie and the History of Radioactivity

After the exciting results of Marie's early experiments Pierre abandoned his study of crystals to join her in her search for new substances. He constructed sensitive laboratory equipment such as this electrometer.

electrometer

The chamber consists of a positive and negative plate connected by an electrometer. Radiation ionises the air in the chamber. The breakdown of air molecules into positive and negative ion pairs allows them to act as carriers of electric current. The negative ions migrate to the positive plate and the positive ions to the negative plate. This causes a weak electric current to flow which can be measured on the electrometer. The level of radioactivity will determine the strength of the current.

The couple laboured over their work, Marie carrying out the chemical separations and Pierre taking the measurements. In July 1898, using basic chemical refining methods, they isolated a product from pitchblende about 400 times more active than uranium. This they named polonium in honour of Marie's native Poland.

Marie later recalled that 'it was exhausting work to move the containers about, to transfer the liquids and to stir for hours at a time, with an iron bar, the boiling material in the cast iron basin'.

They continued with the painstaking refining and by December 1898 the couple announced the discovery of an even more radioactive substance in pitchblende which they called radium. This discovery had far-reaching effects; opening up the fields of radiotherapy and nuclear medicine.