George Hoyt Whipple

George Hoyt Whipple was born on August 28, 1878 in Ashland, New Hampshire. His father, Ashley Cooper Whipple, and paternal grandfather, Solomon Mason Whipple, were both country doctors. When Whipple was two years old his father died of pneumonia and he was raised by his mother and grandmother. As a boy he enjoyed spending time out doors, hunting and fishing which he did throughout his life. Through prep school and college he earned money for his education during breaks and summers providing help and service to tourists to Squam Lake and Lake Winnepesaukee in New Hampshire. He attended Andover Academy and Yale University, graduating with an A.B. in 1900.

Intending to become a physician like his father and grandfather he took a year off from school and earned money for medical school working at Dr. Holbrook's Military School in Ossining, New York, where he taught mathematics and science and served as an athletics coach. In 1901 he entered Johns Hopkins University Medical School. He did so well in his first year anatomy and physiology classes that he won the chance to serve as a student assistant in those classes in his second year. During medical school Whipple became fascinated with pathology, studying the effects of disease on tissues. He graduated medical school in 1905. Graduating fourth in a class of fifty four, he had his choice of internships and choose to stay at Johns Hopkins as a pathology assistant until 1907.

In 1907 Whipple went to Panama and worked as a pathologist at Ancon Hospital, later named Gorgas Hospital, during the building of the Panama Canal. In 1908 he returned to Johns Hopkins first as an assistant, and later an instructor, a associate and associate professor of pathology. In 1914 he was appointed professor of research medicine and director of the Hooper Foundation for Medical Research at the University of California. He was dean of the University of California Medical school from 1920 to 1921. In 1921 he became the dean of the then newly founded and yet to be built medical school at Rochester University. He he served as dean until 1954 and remained at Rochester University, as a professor of pathology, the rest of his life.

Whipple's research was concerned with anemia and the physiology and pathology of the liver. His experiments with anemic dogs revealed that a diet of liver reversed the effects of the anemia. Whipple found that diets of meat were more effective in curing anemia than vegetable diets, but cooked apricots were surprisingly effective. His research led William Murphy and George Minot to experiment with liver diets for people suffering from pernicious anemia, which cured it. Whipple, Murphy, and Minot were awarded the Nobel Prize in 1934 for "their discoveries concerning liver therapy in cases of anemia". Whipple was also the first to describe Whipple's disease, a rare infectious disease caused by the bacterium Tropheryma whipplei.

Whipple died on February 1, 1976.

References:

Miller, Leon L.; "George Hoyt Whipple: 1878-1976"; Biographical Memiors; National Academy Press; 1995

George Hoyt Whipple, Nobel biography

George Hoyt Whipple, Wikipedia entry

Jean Servais Stas

Jean Servais Stas was born on August 21, 1813 in Leuven, Belgium. His father was a locksmith. Due to his delicate health he was predisposed to an academic career. Initially he trained as a doctor at the University of Leuven, because at the time it was the only field of study at the university that taught laboratory science and he obtained a medical degree in 1835. After graduation he switched to chemistry, working for Jean-Baptiste Dumas. In Dumas' laboratory Stas assisted in the most accurate, at the time, determination of the atomic weight of carbon.

In 1840 Stas was appointed professor at the Royal Military School in Brussels. He continued measuring atomic weights, using Oxygen, at 16, as a standard. He proved that atomic weights for elements were not all multiples of 1, the atomic weight of hydrogen, disproving the theory of English physicist William Prout that all the atomic weights were multiples of that of hydrogen. These careful measurements by Stas helped form the basis of the periodic system developed by Dimitri Mendeleev and other chemists.

The atomic mass of an atom is equal to the number of protons and neutrons found in its nucleus minus a small amount of mass for binding energy. The atomic mass of elements used by chemists today are averages, weighted for the various naturally occurring isotopes of the element. For example chlorine has two naturally occurring isotopes, chlorine-35 and chlorine-37. About 76% of naturally occurring chlorine is chlorine-35, so the weighted average used for chlorine in chemical calculations is 35.45. And this is an example of why Stas, in his measurements, did not always get integer results.

Stas is also responsible for one of the world's first toxicology findings. In 1850 the Belgian authorities requested the help of Stas in providing evidence in the prosecution of Count Bocarme. Bocarme, in order to secure for himself the family fortune, had poisoned his brother-in-law by force feeding him nicotine that he had extracted from tobacco. Stas developed a method for isolating alkaloids from human tissues and was able to isolate nicotine from the corpse of Count Borcame's brother-in-law. Stas' evidence was used in the trial and helped convict Count Bocarme of murder. Honors won by Stas include induction into the Royal Society of London, as a foreign member and the Davy Medal, from the Royal Society, for his researches into atomic weights.

Stas died on December 13, 1891

References:

Stratmann, Linda; "Tobacco and Crime: Linda's Crime Notes"; at visart.be

Timmermans, Jean; "Jean Servais Stas"; Journal of Chemical Education(1938)15:353

Jean Servais Stas Wikipedia Entry

Arthur Jeffery Dempster

Arthur Jeffery Dempster was born on August 14, 1886 in Toronto, Canada. His parents were James and Emily (Cheney) Dempster. As a young man he had a wide field of interest, wining multiple scholarships in different subjects. He went to the University of Toronto, earning bachelors and masters degrees in 1909 and 1910 respectively. His first scientific publication was a paper on Darwin's tidal theory.

In 1911 Dempster went to Germany where he first spent a semester each at the Universities of Munich and Gottingen, then went on to spend two years at the University of Wurzburg studying under Wilhelm Wien. Wien was studying the deflection of positive ion beams by electric and magnetic fields. Dempster began to work on a Ph.D. thesis but his studies were interupted by the outbreak of the first world war. Being a British subject, Dempster was forced to flee Wurzburg and left on the last train carrying civilians before the general mobilization. Another Canadian student who made the choice to stay spent four years in an internment camp. Dempster decided to finish his doctorate at the University of Chicago, where he finished in 1916, graduating summa cum laude.

After briefly serving in the Army during World War I and being naturalized as a U.S. citizen he returned to the faculty of the University of Chicago in 1916 and was made full professor in 1927. Dempster remained at the University of Chicago until his death in 1950. Dempster continued studying positive ion rays and using the properties of these rays in 1918 he developed the first modern mass spectrometer. In 1912 J.J. Thompson had developed a mass spectrometer which he used to show that stable elements have can have multiple isotopes, but it was Dempster who perfected it. His mass spectrometer was over 100% more accurate than Thompson's.

A mass spectrometer is an instrument that seperates chemical species by their atomic weight. A sample put into a mass spectrometer is first vaporized and then ionized (electrons are removed making positive ions). After ionization it is seperated by atomic mass by means of electric and magnetic fields. Because the heavier elements are less easy to move using electric or magnetic fields they can be seperated from lighter elements. Using this instrument in 1935 Dempster discovered uranium-235, an isotope of uranium lighter than uranium-238, which made possible atomic energy. Uranium-235 has only a 0.7% abundance in naturally ocuring uranium.

From 1943 to 1946 Dempster was the chief physicist of the University of Chicago's Metallurgical Laboratory, a laboratory specialy purposed to develop the materials neccessary for the production of atomic weapons. Honors won by Dempster include election to the National Academy of Science, a prize from the American Association for the Advancement of Science, and the Lewis Award from the American Philisophical Society.

Dempster died from a heart attack while vacationing in Florida on March 11, 1950.

References:

Allison, Samuel King; "Arthur Jeffrey Dempster: 1886-1950"; Biographical Memoirs; National Academy Press (1952)

"Arthur Jeffrey Dempster, Physicist, 63, Dead"; New York Times; March 12, 1950

Arthur Jeffery Dempster Wikipedia Article

Germain Henri Hess

Germain Henri Hess was born on August 7, 1802 in Geneva, Switzerland. His family moved to Russia when his father, an artist, became a tutor for a rich family. He studied medicine at the University of Tartu, obtaining a M.D. in 1826. In school he also studied chemistry and geology and upon graduation traveled to Stockholm, Sweden to study under the chemist Jons Jakob Berzelius. Although Hess spent only one month in the lab of Berzelius, they became life-long friends and correspondents.

On his return to Russia, Hess took part in a geological expedition to the Urals. After the expedition Hess set up a medical practice in Irkutsk where he remained for two years. In 1830 Hess moved to St. Petersburg where he began teaching chemistry and doing research. Later he became a professor at the St. Petersburg Technological Institute. He remained in St. Petersburg for the remainder of his life.

Hess is most famous for the chemical law that bears his name: Hess's Law. The law is that the enthalpy of change for a chemical reaction that is carried out in a series of steps is equal to the sum of the enthalpies of change of each of the steps. Enthalpy is the heat generated or lost by a chemical reaction. Hess's law allows for the calculation of how much heat will be released or absorbed by a chemical reaction by summing up the enthalpies of each of the steps of the reaction. Hess's Law was an early law in thermochemistry, the study of energy and heat in chemical reactions.

Other discoveries made by Hess include the discovery that sugar when oxidised yields saccharic acid. The mineral Ag₂Te is named Hessite in his honor. Hess wrote the chemistry textbook that was the standard Russian chemistry text for several decades. He was forced to retire due to failing health in 1848.

Hess died in St. Petersburg on December 13, 1850.

References:

Culp, Bartlow; "Germain Henri Hess"; at chemistry.explained.com

Germain Henri Hesse Wikipedia Entry