Henri Becquerel

Henri Becquerel was born on December 15, 1852 in Paris, France. He was born into a family of scientists. His grandfather, Antoine Cesar Becquerel, invented an electrolytic method for extracting metals from their ores and his father, Alexander Edmund Becquerel, a professor of applied physics was known for his work on solar radiation and phosphorescence. Becquerel attended the Ecole Polytechnique in 1872 and the Ecole des Pontes at Chaussees from 1874 to 1877 where he studied engineering. After graduation he worked as a engineer for the Department of Bridges and Highways. In 1876 he became an assistant teacher at the Ecole Polytechnique. In 1895 he became the chair of physics. He also worked as an assistant naturalist at the Museum of Natural History. When his father died in 1891 he assumed his position as the professor of physics at Museum of Natural History.

Becquerel's research covered a number of physics topics. His first work was the rotation of polarized light rays using magnets. Next he began researching phosphorescent materials following in the footsteps of his father. He studied phosphorescent materials by exposing them to sunlight and then exposing them to photographic plates. He was conducting an experiment with uranium. First he would expose it to sunlight and them place it in with a photographic plate. He noticed that the uranium fogged the picture produced. He found he could block the fogging by inserting coins between the uranium and the photographic plate. An experiment run on February 27 and 28, 1896. The weather was overcast when he exposed his uranium salts and so he expected only a faint fogging on the developed photographic plate. Instead he was surprised to find the fogging as severe as it would be from uranium exposed to the sun. This radiation produced by the uranium did not need to be illuminated with sunlight to be produced. The new rays that were produced by the uranium were named Becquerel rays.

Becquerel determined that the rays ionized gasses and could be bent by a magnetic field, unlike x-rays which had recently been discovered by Wilhelm Rontgen. Becquerel determined that the particles emitted by the uranium salts were identical to the electrons discovered by Joseph John Thomson. Becquerel named the particles beta particles. For his discovery of spontaneous radioactivity Becquerel shared the 1903 Nobel Prize in physics with Marie and Pierre Curie. Becquerel had given the breakdown products of his uranium salts to the Curies, who discovered polonium and radium in them. Other honors won by Becquerel include election to French Academy of Sciences in 1889. He was made an officer in the Legion of Honor in 1900.

Becquerel died on August 25, 1908.


References:

Steinman, Rebecca; "Henri Bequerel"; in Biographies of Atomic Scientists

Henri Becquerel Nobel Biography

Henri Becquerel Wikipedia Entry

Martin H. Klaproth

Martin Heinrich Klaproth was born on December 1, 1743. The second son of a citizen of Wernigerode, who lost all his wealth in a tragic fire in 1751, Martin was forced to sing in the church choir in order to subsidize his studies. Originally he intended to enter the clergy like his older brother, but when faced with hard treatment by his instructors he resolved to study to be an apothecary. He then spent five years as an apprentice and worked for two years in the public laboratory in Quedlinburgh. However it was not until 1766, when he worked at the public laboratory in Hanover that he was able to have access to current scientific texts. This awakened his interest in science. In 1782 he became the pharmaceutical assessor at a medical school in Berlin and in 1810 he was appointed professor of chemistry at the newly founded University of Berlin.

At his time, Klaproth was the leading chemist in Germany. He was one the first non-French adherents to the antiphlogistic theories of Lavosier and in the course of his research Klaproth was the first to describe the elements uranium, zirconium and cerium, although he did not obtain the elements in pure metallic form. He also confirmed the existence of titanium as an element. His exact experimentation and use of quantitative methods did much to develop analytical chemistry and mineralogy.

Klaproth is best remembered for his discovery of uranium, which he named after the newly discovered planet Uranus, rather than after himself which was the custom at the time. In 1789 he was examining waste product from St. Joachimstahl and noticed that the stuff associated with lead. When he heated it in solution a yellow crystal was produced, which was unlike anything he had ever seen before. He added wax and a little oil to produce a heavy grayish residue which he identified as a new element. This was uranium.

Klaproth has a crater on the moon named after him.

For his work in analytical chemistry and his discovery of uranium Martin Klaproth is the Dead Scientist of the week for the week of November 29-December 5, 2009


References:

Martin Klaproth Wikipedia Entry

Zoellner, Tom; Uranium: War, Energy and the Rock That Shaped the World; Viking Adult; 2009

Fischer, E. G.; Memoir of the Life of Martin Henry Klaproth; Edinburgh Philisophical Journal; (1821) Vol. 5, Part 2, Issue 10, p.319-334