Monday, November 30, 2009
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
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
Sunday, November 22, 2009
Julius Robert von Mayer, born on November 25, 1814, was one of the pioneers of thermodynamics for enunciating one of the first formulations of the First Law: "Energy can not be created or destroyed".
Mayer grew up in Heilbronn, in southern Rhineland, the son of a pharmacist he studied medicine at the University of Tubingen. After attaining his doctorate, he signed on as ship's physician on Dutch three-masted sailing ship on a trip to Jakarta.
This trip spurred his interest in the physical sciences. His observation that wind swept waves were warmer than calm seas led him to wonder about the physical phenomenon of warmth. Also while in the tropics he observed that the blood of his patients was redder than it would be in northern climes. While operating on a patient he saw the redder blood and feared he had severed an artery. Only after being reassured by local physicians did he realize that this was normal. In the tropics not as much oxygen is required to warm the body and thus the blood traveling back to the heart is more oxygenated and redder than venous blood in cooler climes where more oxygen is required to maintain temperature. This led Mayer to believe that oxidation was the primary source of energy in living things.
Upon returning to Germany Mayer wrote a paper outlining his observations, however the paper contained no experimental results and was rejected. Unable to get clarification on why his paper was rejected Mayer (relying on the experimental work of others) wrote another paper in which he proposed that mechanical energy and heat energy were equivalent, specifically that the dropping of a weight from 365meters was equivalent to warming an equivalent mass of water from 0 to 1 degree Celsius. The current accepted value for this standard is 418.4meters.
At the time Mayer's work was largely ignored and credit for the discovery of the equivalence of mechanical and heat energy was initially given to James Joule (for whom the unit of energy is named). In 1848 when Mayer tried to assert his precedence, Joule admitted Mayer's precedence but claimed credit for the experimental demonstration of the theory. This controversy, plus the loss of two of his children, caused Mayer to attempt suicide in 1850. Mayer's work led Herman von Helmholtz to formulate the general principal of conservation of energy in 1848.
For his work in describing the principal of the conservation of energy Julius Robert von Mayer is the Dead Scientist of the Week for the week of November 22-28, 2009.
Julius Robert von Mayer Wikipedia Entry
Mechanical equivalent of heat Wikipedia Entry
Cobb, Kathy; Goldwhite, Harold; Creations of Fire: Chemistry's Lively History from Alchemy to the Atomic Age; Basic Books, 2002
Sunday, November 15, 2009
James B. Sumner, born on November 19, 1887 in Canton, MA, was the first person to isolate an enzyme. While he was growing up he was an avid hunter and lost his right arm below his elbow in a hunting accident. Having been left handed, this forced him to adapt to using his right hand to do things and this effort allowed him to become an expert at tennis, skiing, billiards and clay-pigeon shooting.
As an undergrad at Harvard College he specialized in chemistry. He then went on to study Biochemistry at Harvard Medical School from which he obtained his Ph.D. in 1914. Offered an assistant professorship at Cornell Medical School he went there where he was made a full professor in 1929.
His research at Cornell centered around analytical methods, but despite hard work he was unable to obtain any interesting results. He then decided to try to isolate an enzyme, a feat which until then many of his colleagues thought was impossible. In 1921, when he work was still in the early stages he received a fellowship to travel to Belgium. He wanted to go there to work with Jean Effront, who had written several books on enzymes, however Erront thought the idea of isolating an enzyme was ridiculous, so the trip fell through.
In 1926 he finally succeeded in isolating the enzyme urease. Many biochemists disbelieved or ignored his results, but in 1929 it brought him a full professorship. In 1929 John Northrop of the Rockefeller Institute isolated pepsin and subsequently other enzymes it became clear that Sumner had developed a general method for isolating enzymes. Other biochemists gradually were forced to admit Sumner's claims were correct. For his work demonstrating that an enzyme could be isolated Sumner, along with Northrop, were awarded the Nobel Prize for Chemistry in 1946.
Sumner's work demonstrated that enzymes were proteins, which at the time was controversial. Enzymes function as catalysts in biological systems. They allow chemical reactions, particularly those of metabolic pathways, to occur much faster than they would under normal conditions. Enzymes speed chemical reactions by lowering the activation energy required for a reaction to occur. Enzymes are also specific, in that they will only catalyze a specific chemical reaction. For example Urease (the enzyme isolated by Sumner) catalyzes the conversion of urea into carbon dioxide and ammonia and it occurs in bacteria, yeast and some higher plants. An article with more information about enzymes can be found here.
For his research in isolating enzymes, James Sumner is the Dead Scientist of the Week for the Week of November 15-21, 2009.
James Sumner Wikipedia Entry
James Sumner Nobel Biography
Enzymes Wikipedia Entry
Urease Wikipedia Entry
Sunday, November 8, 2009
Born on November 10th in 1764 Andres Manuel Del Rio was the Spanish-Mexican mineralogist who discovered the element vanadium.
After his studies in Spain, Germany, and France (where he studied under Antoine Lavoisier) Del Rio was appointed to the College of Mines in New Spain (Mexico) as the chair of chemistry and mineralogy. It was there he taught the first course of mineralogy offered in New Spain.
In 1801, while examining samples from a mine in Zimpan, he arrived at the conclusion that he had found a new metallic element. He prepared various compounds of the new element which he named pancromium. Later, upon observing that when the compounds were heated, he decided on the name eritronium (Eritros is red in Greek). A year later he sent the samples to Alexander von Humbolt, who sent them to Hippolyte Victor Collet-Descotils who analyzed the samples and found only chromium, causing Del Rio to claim that his discovery had been in error.
Later, in 1830, Swedish chemist Nils Gabriel Sefstrom rediscovered the element, which he named Vanadium after the Scandinavian goddess of love and beauty Vanadis. In the same year German chemist Friedrich Wholer analyzed Del Rio's samples and found that eritronium and vanadium were the same.
Vanadium is an example of a transition metal. Transition metals are the elements found in the middle part of the periodic table (see a periodic table here where the transition metals are in green). These elements are very hard in their elemental from with high melting and boiling points. In this part of the periodic table the electrons in the loosely held d-orbitals are being filled in which make transition metals malleable and able to conduct electricity.
For his discovery of the element Vanadium, Andres M. Del Rio is the Dead Scientist of the week for the week of November 8-14, 2009.
Andres Manuel Del Rio Wikipedia Article
Sunday, November 1, 2009
Born on November 7 1878 Lise Meitner played an important part in the discovery of atomic fission. She was the second woman to obtain a doctoral degree in physics from the University of Vienna.
At the time many male scientists did not approve of women in science and her career was hampered (including her being omitted from the Nobel Prize in 1944 for her work in discovering the nuclear chain reaction of atomic fission according to some historians).
Because of her Jewish ancestry (she had been baptised a Protestant in 1908) she was forced to flee Germany in 1938 (after the German annexation of Austria). In Holland she was unable to get a position so she went to Stockholm, Sweden where she got a position in Manne Siegbahn's laboratory.
Working in Sweden she corresponded with her cousin Otto Hahn who she had worked with before she fled Germany and clandestinely traveled to Copenhagen in November 1938 and after corresponded with Hahn to design a set of experiments that Hahn would later carry out that would provide evidence of nuclear fission of uranium.
Nuclear fission is the process by which the nuclei of large atoms break down into smaller nuclei. Large nuclei (with high number of protons) will break down into smaller nuclei because the large amount of electrostatic repulsion (positive protons repelling each other) overcomes the strong nuclear force which holds the nucleus together. Meitner (along with her nephew Otto Frisch) discovered why no elements larger than uranium naturally occur; the electrostatic repulsion of so many protons is so great it overcomes the strong nuclear force which holds the nuclei together. She was able to explain the large amount of heat energy produced by a nuclear chain reaction and realized that this process could be used to produce atomic weapons.
A nuclear chain reaction occurs when a one nuclear reaction causes one or more nuclear reactions to occur. For example when a uranium nucleus breaks down it releases neutrons which bombard other uranium nuclei and cause them to break down. In turn when these nuclei break down they release neutrons that cause more uranium nuclei to break down. This self perpetuating process produces thousands of times more energy than any chemical reaction. The rate at which this process occurs can be controlled by absorbing some of the neutrons and thus slowing the reaction. In nuclear power plants this is done by inserting control rods which absorb neutrons. In nuclear weapons the process is allowed to continue without moderation.
For her work discovering the nuclear fission and the nuclear chain reaction Lise Meitner is the Dead Scientist of the Week for the week of November 1-7, 2009
Lise Meitner Wikipedia entry
Splitting of the Atom at sjmv.org
Lise Meitner: A Battle for Ultimate Truth at sdsc.edu
Nuclear Chain Reaction Wikipedia Entry