Georg Brandt

Georg Brandt was born on July 21, 1694 in Riddarhyttan, Sweden. His father, Jurgen Brandt, was a metalworker and an apothecary. Growing up he assisted his father with his metalwork projects and he became interested in it. Brandt attended Uppsala University and worked for the council of mines. In 1721 he traveled to Leiden where he worked in the laboratory of Herman Boerhaave for three years. There he studied chemistry and medicine. He earned a medical doctorate from the University of Rheims in 1726. When he returned home to Sweden he was made the director of laboratory of the Council of Mines. Brandt was named warden of the Royal Mint in 1730. He became an associate member of the council of mines in 1747 and a full member in 1750.

Brandt's research involved investigating metals. He coined the term semi-metals to describe elements that have both metal and non-metal characteristics. These elements are now called metalloids. Metaloids are the elements in the region between metal and non-metal elements on the periodic table (see here) In 1733 he investigated arsenic and its compounds. In 1735 he postulated that the blue color in an ore known as smalt was due to an unknown metal or semi-metal. In 1742 he was able to isolate this unknown blue metal which he named cobalt, taking the name from the old Teutonic word kobold meaning demon. Cobalt is atomic number 27 and is represented by the chemical symbol Co.

Brandt's later research involved using hot acid solutions to dissolve gold. Brandt's later publications dealt with criticism of the alchemical belief that other "base" metals could be transformed into gold. It has been said that he did more than any other chemist to clarify that transmutation of other metals into gold was impossible and that claims of alchemists that they could create gold from other metals were false.

Brandt died on April 29, 1768 in Stockholm, Sweden of prostate cancer.


References:

Morris, Richard; The Last Sorcerers; Joseph Henry Press; 2003

"Brandt, Georg" in Complete Dictionary of Scientific Biography; Charles Scribner's Sons; 2008

Georg Brandt Wikipedia Entry

Jean-Baptiste Dumas

Jean-Baptiste-Andre Dumas was born on July 14 (Bastille Day), 1800 in Ales, France. His father worked as a clerk in the municipality of Ales. Initially his family prepared him for a naval career, but with the bloodshed that followed the downfall of the Napoleonic empire he was apprenticed to an apothecary. Wishing to leave his home in 1816 he traveled to Geneva on foot, where he attended lectures on science. The apothecary where he worked provided a laboratory where he could perform experiments. In 1821 Dumas went to Paris where he completed his studies in chemistry. Two years later Dumas was appointed lecture assistant to Louis Jacques Thenard, a professor at the Ecole Polytechnique.  Dumas succeeded him two years later.

During the 1820s Dumas developed a method of measuring the vapor densities of volatile liquids which he used to measure the atomic weights of 30 of the 59 the elements known at the time. Starting with the hypothesis of William Prout, that the atomic mass of hydrogen was 1 and all the other elements were multiples of hydrogen's mass, Dumas determined the masses of the other elements. Later Dumas began work on organic chemistry (chemistry involving compounds of carbon) going on to become one of the most advanced organic chemists of his time. In 1833 Dumas developed a method for determining the amount of nitrogen in an organic compound, founding modern analytical chemistry.

Dumas also studied physiological questions. In one of his first researches he determined that iodine was what was necessary factor to treat goiter. He also determined that kidneys removed urea, a form of nitrogen waste, from the blood.

When he reached middle age Dumas devoted more of his time to public service and less time to scientific research. He served as the minister of agriculture and commerce and as director of the mint. He was also served as a senator.

Dumas died on April 10, 1884 in Cannes. He was buried in Paris and his is one of the 72 names memorialized on the Eiffel Tower.


References:

Anon; Obituary; Proceedings of the Royal Society; (1884) 37:X

Cooke, Josiah Parsons; "Jean-Baptiste-Andre Dumas"

Newbold, Brian; "Jean-Baptiste-Andre Dumas: A Dominating Influence in Nineteenth Century French Chemistry";

Jean-Baptiste Dumas Wikipedia Entry

Nettie Stevens

Nettie Maria Stevens was born on July 7, 1861 in Cavendish, Vermont. Her family settled in Westford, Vermont, where her father was a carpenter and handyman. He did well enough that he was able to invest in real estate and he was able to send his children away to school. Stevens attended Westfield Academy and Westfield Normal School where she completed a four year program in two years. After working as a teacher for a while, in 1896 Stevens began attending Stanford University, in Palo Alto, California, where she earned a BA in 1899 and a MA in 1900 completing her thesis using a microscope to describe new species of marine life. Stevens next went to Bryn Mawr College where she studied cytology. While at Bryn Mawr Stevens won a fellowship that allowed her to travel to Warzburg, where she studied in the laboratory of Theodore Boveri. Boveri was studying the role that chromosomes have on heredity. Stevens returned to Bryn Mawr finishing her PhD in 1903. After finishing her doctorate she remained at Bryn Mawr as an assistant.

Stevens research while at Bryn Mawr was studying the chromosomes of sex cells of meal worms. Sex cells are the cells produced by males and females that give rise to progeny. These cells have half the number of chromosomes that normal cells do. When male and female sex cells combine, a process called fertilization, it gives rise to a single cell with half of its chromosomes from the father and half from the mother that will eventually develop into progeny. Stevens noted in her research that some male sex cells have a chromosome not found in female sex cells. She proposed that this extra chromosome was responsible for determining the sex of the offspring. Today we call this extra chromosome the Y-chromosome and when a male sex cell, with a Y-chromosome, fertilizes an egg the offspring will be male. Half of male sex cells have an X-chromosome and when it fertilizes a female sex cell the offspring will be female. At the time it was believed that the gender of offspring was determined by the mother and environmental factors and Stevens' research was not widely accepted. Today we know that the sex cells of the father, with either Y or X chromosomes, determine the gender of the offspring through the mechanism discovered by Stevens.

Stevens died of breast cancer on May 4, 1912 at the early age of 39.


References:

DNA Learning Center; "Nettie Maria Stevens (1861-1912)"; Retrieved from: dnaftb.org

Scitable; "Nettie Stevens: A Discoverer of Sex Chromosomes"; Retrieved from: nature.com

Nettie Stevens Wikipedia Entry

Lawrence J. Henderson

Lawrence Joseph Henderson was born on June 3, 1878 in Lynn, Massechusets. His father Joseph was a businessman. Henderson went from being an undersized infant to an athlete who was known for his running speed. Henderson attended school in Salem, Massachusetts and entered Harvard College at the age of 16. He was fond of mathematics and physics and did well in those subjects. He earned his A.B. degree in 1898 and entered Harvard Medical School later that year. He earned his MD in 1902 and afterwards spent two years working in Franz Hofmeister's laboratory at the University of Strasbourg. When he returned to the United States he took a lecturer position at Harvard Medical School. He would remain at Harvard for the rest of his career, as an instructor from 1905-1910, as an assistant professor of biological chemistry from 1910-1919, as a professor from 1919-1934 and as the Abbot and James Lawrence professor of biological chemistry from 1934 until his death.

Henderson's initial research interest upon returning to America was in understanding buffer systems and how the human body maintains its pH balance. In the blood carbon dioxide from cellular respiration combines with water to form carbonic acid. Carbonic acid (H₂CO₃) exists in the blood primarily in the form of bicarbonate (HCO₃^-). Bicarbonate and the proteins of the blood act as buffers that maintain the body's pH. When excess acid or base is produced bicarbonate acts to maintain the body's pH at a slightly basic pH (about 7.35). From his research on buffers Henderson developed an equation that can be used to calculate the pH of a buffer system. The Henderson/Hasselbalch equation equates the pH to the pKa of the acid in the buffer plus the log of the concentration of the acid's anion divided by the concentration of the associated acid (pH = pKa + log([A^-]/[HA]).

Henderson's later research career dealt with more philosophical issues in science. He published two books, The Fitness of the Environment and The Order of Nature, devoted to the discussion of global problems of the fitness of organisms in their environments. In The Order of Nature he concluded that "the whole evolutionary process, both cosmic and organic, is one, and the biologist may rightly regard the universe, in its essence as biocentric."

Henderson died on February 10, 1942 in Cambridge, Massachusetts.


References:

Cannon, Walter M.; "Biographical Memoir of Lawerence Joseph Henderson 1878-1943"; National Academy Press; 1943

Mayer, Jean; "Lawrence J. Henderson - A Biographical Sketch"; The Journal of Nutrition (1968)94:3-5

Smith, Charles H.; "Henderson, Lawrence Joseph (United States 1878-1942)"; retrieved from: http: wku/people.wku.edu/charles.smith

Lawerence Joseph Henderson Wikipedia Entry

Johannes Wislicenus

Johannes Winlicenus was born on June 24, 1835 in Kleineichsted, Saxony, the son of Gustav and Emilie Winlicenus. He was born into a devout protestant family that in the 17th century had been forced to flee their native Poland to Saxony on account of their religion. His father was a protestant minister who in 1853 published a book in which he attempted to liberate people from what he thought was a "superstitious adoration" of the Bible. The book was considered blasphemous by the authorities, and so it was destroyed and he was sentenced to two years in prison. Instead he fled with his family to Boston, Massachusetts. Johannes who was 18 at the time served as an assistant to chemist Eben Horsford at Harvard University and in 1855 he as appointed lecturer at New York's Mechanic's Institute. Returning to Europe in 1856 he went to the University of Halle where he resumed his studies and served as an assistant to Wilhelm Heintz. He had finished the requirements for his PhD by 1859 but as a condition of his graduation he was asked to renounce the teachings of his father and cease his political activities. He refused and then went to the University of Zurich where he finished his doctorate in 1860. He served as a lecturer at the University of Zurich until 1868 when he became a professor of chemistry there. In 1860 he became professor of chemistry at the Swiss Pyrotechnical Institute and he served both professorships simultaneously. In 1872 he became the chair of chemistry at the University of Wurzburg and in 1885 he became a professor of chemistry at the University of Leipzig.

Winlicenus' research was in organic chemistry. Starting in 1868 he began studying lactic acid. Lactic acid is a  carboxylic acid that is a metabolite of glucose. In his studies he found that there were two types of lactic acid which had different chemical properties. While these two chemicals have the same chemical formula (the same numbers and types of atoms) they have different structures. In the case of lactic acid (a three carbon long carboxylic acid) one form has a hydroxyl group attached to the carbon adjacent to the carbonyl carbon and the other form has a hydroxyl group attached to the terminal carbon, the carbon on the opposite end of the three carbon chain from the carbonyl. Because these two molecules have different structures they have different properties, but the formulas for both compounds are both C3H6O3. Winlicenus called these chemicals with the same formula but different structures structural isomers.

Another important experiment carried out by Winlicenus, working in collaboration with his friend Aldolf Fick a professor of physiology at the University of Zurich, showed that carbohydrates and fats were the principal source of muscular energy. The pair ascended the Faulhorn, taking with them only food from which proteins had been excluded. While they climbed the pair monitored their nitrogen metabolism and found that the the break down of proteins accounted for less than one third of the energy generated by their metabolism.

Wislicenus was elected a foreign member of the British Royal Chemical Society in 1888 and member of the Royal Society of London in 1897 which presented him with its Davy Medal in the following year.

Winlicenus died on December 5, 1902.


References:

P.F.F.; "Johannes Wislicenus. 1835-1902"; Proceedings of the Royal Society (1907) 78:iii-xii

Ramberg, Peter J.; Chemical Structure, Spatial Arrangement: An Early History of Stereochemistry. 1874-1914; Ashgate Publishing Ltd.; 2003

"Johannes Wislicenus, Biography", retrieved from: my.rsc.org

Johannes Wislicenus Wikipedia Entry

Giovanni Cassini

Giovanni Domenico Cassini was born in Perinaldo in northern Italy on June 8, 1625. He was brought up by his maternal uncle who looked after his education. He attended school in Valebone for two years and then attended the Jesuit college in Genoa where he studied astrology and astronomy. Although he studied astrology he admitted that it was not prophetic but at the time there was little separation between astronomy and astrology. In 1644 he was invited to become an assistant at the Bologna Observatory and six years later, when he was still only 25, he was made professor of astronomy and mathematics at the University of Bologna. In addition to his astronomical work, Cassini also did river engineering work and engineered fortifications for the Holy See. In 1668 he was invited to help set up the new Paris Observatory by Louis XIV of France. Pope Clement IX agreed to the trip believing it would be short, only two years at the most. Cassini once established in the new observatory made no effort to return to Italy. He remained at the Paris Observatory and three generations of his descendants ran it until 1794.

Cassini is probably best remembered for discovering the Cassini Division, a open space between Saturn's A and B rings. Before Cassini it was believed that the rings of Saturn were one large solid ring structure orbiting the planet. Cassini's observations of the rings showed that there were breaks between the rings. We know now that the rings of Saturn are not solid at all, but made up of orbiting pieces of ice and debris. Cassini was also responsible for identifying four of the moons orbiting Saturn: Iapetus, Rhea, Tethys, and Dione. Cassini also shares credit for discovering the red spot on Jupiter with English scientist Robert Hooke Although Cassini initially believed in a geocentric model for the solar system he eventually came to believe in a solarcentric model, similar to that proposed by Nicolas Copernicus.

In addition to craters on the moon and Mars named after him Cassini also has an asteroid named after him. Additionally NASA's unmanned probe that is currently exploring Saturn and its moons is named after him (for more information on the Cassini probe see here).

As he grew older Cassini's vision failed him and his son Jacques began to run the Paris Observatory. Cassini died on December 14, 1712.


References:

Connor, Elizabeth; "The Cassini Family and the Paris Observatory"; Astronomical Society of the Pacific Leaflets (1947)218:146-153

O'Connor, J.J. and Robertson, E.F.; "Giovanni Domenico Cassini"; Retrieved from: history.mcs.st-anderews.ac.uk

Giovanni Domenicao Cassini Wikipedia Entry

Otto Loewi

Otto Loewi was born in Frankfurt, Germany on June 3, 1873. His father Jacob was a Jewish wine merchant. He attended gymnasium school in Frankfrurt and then the Universities of Munich and Strasbourg as a medical student. Not really interested in clinical medicine, Loewi applied himself to physiology and pharmacology. He completed his thesis on the effects of arsenic, phosphorus, and other substances on an isolated frog heart. After completing his medical education in 1896, Loewi spent a year as an assistant doctor in a hospital in Frankfurt. There he was frustrated by the lack of effective treatment for tuberculosis and pneumonia patients. This convinced him that he did not want to practice clinical medicine and opted instead for a research career. He was able to get a position as an assistant to Hans Meyer starting work in Meyer's laboratory in Marburg in 1898. Working in Meyer's lab he researched metabolism. While working there he proved that animals were able to synthesize proteins from protein degradation products (amino acids). Before that it was believed that animals could only make proteins from other intact proteins.

In 1903 he was appointed professor of pharmacology at the University of Graz in Austria. While working at Graz he conducted an experiment that proved that the transmission of nerve impulses to the heart was conducted by a soluble factor, the idea for which came to him in a dream. First he isolated two frog hearts, one with the vagus nerve still attached. The vagus nerve is part of the parasympathetic nervous system and causes the heart muscle to slow its beating. First he stimulated the attached vagus nerve, which caused the attached heart to slow its beating. Taking a sample of the fluid surrounding the heart with the attached nerve he applied it to the second heart. The second heart slowed its beating in response to the added fluid. Loewi named the unknown soluble factor that caused the second heart to slow its beating "vagustoff". It was later identified as acetylcholine. The transmission of nerve impulses between different neurons and at the nerve interfaces with muscles are conducted by soluble chemicals called neurotransmitters. For his pioneering work establishing the importance of neurotransmitters Loewi shared the 1936 Nobel Prize in medicine and physiology with Henry Dale. He would remain in Austria until 1938 when he was forced to leave due to the German occupation. After a brief stays in Belgium and the United Kingdom, Loewi emigrated to the United States in 1940

Other honors won by Loewi include honorary doctorates from the University of Graz, Yale University, University of New York (where he worked after he emigrated to the United States) and the University of Frankfurt. He was made an honorary member of the Physiological Society of London and a member of the Royal Society.

Loewi died on December 25, 1961.


References:

Valenstein, Elliot S.; The War of Soups and the Sparks: The Discovery of Neurotransmitters and the Dispute Over How Nerves Communicate; Columbia University Press; 2005

Otto Loewi Nobel Biography

Ottto Loewi Wikipedia Entry