Book: Traité de Radioactivité

Overview
"Traité de Radioactivité" (1910) is a comprehensive, two-volume synthesis of the experimental facts and interpretations gathered by Marie Curie and contemporaries about the newly recognized phenomenon of radioactivity. It assembles meticulous measurements, chemical separations, and phenomenological descriptions to define radioactivity as an intrinsic property of certain elements, characterized by spontaneous emission of penetrating rays and by the capacity to ionize surrounding matter. The writing balances careful laboratory detail with broader reflections on what radioactivity reveals about atomic structure and the nature of matter.

Experimental Methods and Measurements
Detailed chapters describe the experimental techniques developed or refined to detect and quantify minute radioactive effects. Sensitive electrometers, photographic plates, and ionization chambers are presented alongside chemical methods for isolating trace quantities of radioactive substances from tons of pitchblende and other minerals. Emphasis falls on reproducible measurement: the correlation between ionization current and the amount of active material, methods for reducing contamination, and the painstaking use of fractional crystallization and precipitation to concentrate radioactive compounds.

Discovery and Characterization of Polonium and Radium
The treatise recounts the isolation and identification of two new elements, polonium and radium, discovered through persistent chemical separation and measurement of activity. Polonium is documented as a faintly active constituent extracted from pitchblende residues, notable for its strong radioactivity relative to its minute quantity. Radium is treated in far greater detail: its preparation as salts, analysis of spectral lines, chemical affinities, and striking physical effects such as intense ionization, persistent luminescence, and measurable heat emission. The narrative conveys the scale of effort required to obtain microgram quantities and the experimental patience that made characterization possible.

Theoretical Implications and Spontaneous Disintegration
The book situates radioactivity within emerging theoretical frameworks, emphasizing that radioactivity is a spontaneous process originating within atoms rather than a transient reaction to external excitation. It engages with the disintegration hypothesis then being developed by Rutherford and Soddy, treating atomic transformation and the emission of new radiations as central explanatory ideas. Discussion addresses how radioactive emissions challenge classical views of immutable atoms, suggest vast internal energy reservoirs, and call for new concepts linking chemistry, physics, and the nascent field of nuclear science.

Physical and Chemical Properties
Beyond detection and isolation, considerable attention is given to the physical and chemical behavior of radioactive substances. The text documents how radiation affects surrounding materials, induces phosphorescence and chemical changes, and produces continuous heat. Chemical studies probe affinities and valences to place radium and polonium within classical chemistry while acknowledging their exceptional behavior. Where measurements could be compared across laboratories, Curie underscores consistency and the need for standard procedures.

Impact and Legacy
The treatise consolidates the empirical foundations of radioactivity and sets methodological standards that shaped radiochemistry and experimental nuclear physics. Its thorough documentation validated the reality of new elements and established experimental protocols that accelerated discovery. The ideas collected here helped persuade scientists that atoms are mutable and energetic, opening pathways to atomic theory, medical applications such as radiotherapy, and later developments in nuclear physics. The work also, implicitly, foreshadows the practical and ethical challenges of working with powerful, invisible emissions, challenges that would only become fully understood in subsequent decades.