Math Is Fun Forum

2416) Calcium Carbonate

Gist

Calcium carbonate (CaCO3) is a common inorganic compound found naturally in rocks such as limestone, marble, and chalk, and is a major component of sea animal shells and eggshells. It is a white, odorless powder that is practically insoluble in water but dissolves readily in acid. 

Calcium carbonate (CaCO3) is a substance widely used for various purposes, for example, as a filler and pigment material not only in paper, plastics, rubbers, paints, and inks but also in pharmaceutics, cosmetics, construction materials, and asphalts and as a nutritional supplement in animal foods.

Summary

Calcium carbonate is a chemical compound with the chemical formula CaCO3. It is a common substance found in rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skeletons and pearls. Materials containing much calcium carbonate or resembling it are described as calcareous. Calcium carbonate is the active ingredient in agricultural lime and is produced when calcium ions in hard water react with carbonate ions to form limescale. It has medical use as a calcium supplement or as an antacid, but excessive consumption can be hazardous and cause hypercalcemia and digestive issues.

Preparation

The vast majority of calcium carbonate used in industry is extracted by mining or quarrying. Pure calcium carbonate (such as for food or pharmaceutical use), can be produced from a pure quarried source (usually marble).

Alternatively, calcium carbonate is prepared from calcium oxide. Water is added to give calcium hydroxide then carbon dioxide is passed through this solution to precipitate the desired calcium carbonate, referred to in the industry as precipitated calcium carbonate (PCC).

In a laboratory, calcium carbonate can easily be crystallized from calcium chloride (CaCl2), by placing an aqueous solution of CaCl2 in a desiccator alongside ammonium carbonate [NH4]2CO3. In the desiccator, ammonium carbonate is exposed to air and decomposes into ammonia, carbon dioxide, and water. The carbon dioxide then diffuses into the aqueous solution of calcium chloride, reacts with the calcium ions and the water, and forms calcium carbonate.

Details

Calcium carbonate (CaCO3) is a chemical compound consisting of one atom of calcium, one of carbon, and three of oxygen that is the major constituent of limestone, marble, chalk, eggshells, bivalve shells, and corals. Calcium carbonate is either a white powder or a colorless crystal. When heated, it produces carbon dioxide and calcium oxide (also called quicklime). Calcium carbonate has a molecular weight of 100.1 grams per mole.

Calcium carbonate occurs naturally in three mineral forms: calcite, aragonite, and vaterite. Calcite, the most common form, is known for the beautiful development and great variety of its crystals. A large percentage of calcite occurs in limestones, and calcite is also the chief component of marls, travertines, calcite veins, most cave deposits, many marbles and carbonatites, and some ore-bearing veins. Calcite is the stable form of calcium carbonate at most temperatures and pressures. Aragonite is the orthorhombic (i.e., having three unequal crystalline axes at right angles to one another) form of calcium carbonate. Though frequently deposited in nature, it is metastable at room temperature and pressure and readily inverts to calcite. Vaterite, the hexagonal form of calcium carbonate, is extremely rare and transforms into calcite or aragonite or both.

Calcium carbonate has many uses. Since ancient times, limestone has been burned to quicklime (CaO), slaked to hydrated lime [Ca(OH)2], and mixed with sand to make mortar. Limestone is one of the ingredients used in the manufacture of portland cement and is often employed as a flux in metallurgical processes, such as the smelting of iron ores. Crushed limestone is used widely as riprap, as aggregate for both concrete and asphalt mixes, as agricultural lime, and as an inert ingredient of medicines.

As marble, calcium carbonate is used for statuary and carvings and is a popular facing stone as polished slabs. The term marble is used differently in the marketplace from the way it is used in geology: in the marketplace, it is applied to any coarse-grained carbonate rock that will take a good polish rather than to metamorphic carbonate-rich rocks exclusively. Some coarsely crystalline diagenetic limestones are among the most widely used commercial “marbles.” Travertine and onyx marble (banded calcite) are also popular facing stones, usually for interior use.

Calcium carbonate obtained from its natural sources is used as a filler in a variety of products, such as paper, ceramics, glass, plastics, and paint. Synthetic calcium carbonate, called “precipitated” calcium carbonate, is employed when high purity is required, as in medicine (antacids and dietary calcium supplements), in food (baking powder), and for laboratory purposes.

Additional Information

Calcium carbonate is an ionic compound used as a calcium supplement or antacid used for the symptomatic relief of heartburn, acid indigestion, and sour stomach.

Calcium carbonate is an inorganic salt used as an antacid. It is a basic compound that acts by neutralizing hydrochloric acid in gastric secretions. Subsequent increases in pH may inhibit the action of pepsin. An increase in bicarbonate ions and prostaglandins may also confer cytoprotective effects. Calcium carbonate may also be used as a nutritional supplement or to treat hypocalcemia.

Calcium carbonate is a basic inorganic salt that acts by neutralizing hydrochloric acid in gastric secretions. It also inhibits the action of pepsin by increasing the pH and via adsorption. Cytoprotective effects may occur through increases in bicarbonate ion (HCO3-) and prostaglandins. Neutralization of hydrochloric acid results in the formation of calcium chloride, carbon dioxide and water. Approximately 90% of calcium chloride is converted to insoluble calcium salts (e.g. calcium carbonate and calcium phosphate).

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2613.

2363) Earl Wilbur Sutherland Jr.

Gist:

Work

Signals between different parts of the body are conveyed by small electrical impulses and by chemical substances, hormones and signal substances. Communication also takes place between different cell parts. Earl Sutherland investigated how hormones, especially adrenaline, work. He showed how signals from one cell to another are conveyed by a messenger—the hormone—and how signals within the cell are then conveyed by another messenger. Around 1960 he showed how cyclic adenosine monophosphate (cAMP) serves as the secondary messenger within the cell.

Summary

Earl W. Sutherland, Jr. (born Nov. 19, 1915, Burlingame, Kan., U.S.—died March 9, 1974, Miami, Fla.) was an American pharmacologist and physiologist who was awarded the 1971 Nobel Prize for Physiology or Medicine for isolating cyclic adenosine monophosphate (cyclic AMP) and demonstrating its involvement in numerous metabolic processes that occur in animals.

Sutherland graduated from Washburn College (Topeka, Kansas) in 1937 and received his M.D. degree from Washington University Medical School (St. Louis, Missouri) in 1942. After serving in the U.S. Army during World War II, he joined the faculty of Washington University. In 1953 he became chairman of the department of pharmacology at Western Reserve University (now Case Western Reserve University) in Cleveland, Ohio, where in 1956 he discovered cyclic AMP. In 1963 Sutherland became a professor of physiology at Vanderbilt University (Nashville, Tennessee), and from 1973 until his death he was a member of the faculty of the University of Miami Medical School.

Details

Earl Wilbur Sutherland Jr. (November 19, 1915 – March 9, 1974) was an American pharmacologist and biochemist born in Burlingame, Kansas. Sutherland won a Nobel Prize in Physiology or Medicine in 1971 "for his discoveries concerning the mechanisms of the action of hormones", especially epinephrine, via second messengers, namely cyclic adenosine monophosphate, or cyclic AMP.

Early life and education

Sutherland was born on November 19, 1915, in Burlingame, Kansas. The second youngest of six children, he was raised by his mother, Edith M. Hartshorn, and his father, Earl W. Sutherland. Though his father, who was originally from Wisconsin, had attended Grinnell College for two years, he ultimately led an agrarian lifestyle that took him to both New Mexico and Oklahoma before settling down in Burlingame to raise a family. Edith, a Missouri native, had some training in nursing at what was called a "ladies college". To provide for the family, Sutherland's father ran a dry goods store, where he gave each of his children working jobs. Sutherland began fishing at the age of five, and this became a pastime that he enjoyed for most of his life.

As a high school student, Sutherland played and excelled in several sports, including tennis, basketball, and football.

In 1933, at the age of 17, Sutherland enrolled in Washburn College in Topeka, Kansas and began the pursuit of a Bachelor of Science degree. In order to pay for tuition, he worked throughout his undergraduate years as a medical staff assistant at a local hospital. Sutherland graduated in 1937, at the age of 21. He was then accepted to Washington University School of Medicine in St. Louis, where he developed a strong mentorship with Carl Ferdinand Cori. In 1942, Sutherland graduated with a Doctor of Medicine.

Career:

Academia and research

In 1940, while studying at the Washington University School of Medicine, Sutherland had his first encounter with research as an assistant in pharmacology in the laboratory of Carl Ferdinand Cori, who won a Nobel Prize in Physiology or Medicine in 1947 for his discovery of the mechanism of glycogen metabolism. Under Cori's guidance, Sutherland conducted research on the effects of the hormones epinephrine and glucagon on the breakdown of glycogen to glucose. In 1942, he worked as an intern at Barnes-Jewish Hospital in St. Louis.

After receiving his medical degree from Washington University in 1942, Sutherland served as a World War II army physician. He returned to Washington University in St. Louis in 1945, where he continued to do research in Cori's Laboratory. Sutherland accredits his decision to pursue a research career, as opposed to entering the medical profession, to his mentor Cori.

Sutherland held various teaching titles during his time at the Washington University School of Medicine, including instructor in pharmacology (1945–46), instructor in biochemistry (1946–50), assistant professor in biochemistry (1950–52), and associate professor in biochemistry (1952–53).

In 1953, Sutherland moved to Cleveland a position as a professor of pharmacology and chairman of the department of pharmacology at the school of medicine at Case Western Reserve University. There, he collaborated with Theodore W. Rall, also a professor of pharmacology, who was to become a lifelong research partner. Together, they conducted further research on the mechanism of hormone action at the molecular level. During his ten years at Case Western Reserve University, Sutherland made several ground-breaking discoveries that led to the identification of cyclic adenosine monophosphate, or cyclic AMP, and its role as a secondary messenger.

In 1963, Sutherland became professor of anatomy at Vanderbilt University School of Medicine in Nashville. His position allowed him to devote more time to his research. He continued his work on cyclic AMP, receiving financial support from the Career Investigatorship awarded to him by the American Heart Association in 1967. He held his teaching title at Vanderbilt University until 1973.

In 1973, after spending 10 years at Vanderbilt University, Sutherland moved to Miami, where he joined the faculty at Miller School of Medicine at the University of Miami as a distinguished professor of biochemistry. He continued to be involved in novel research about adenosine monophosphate and guanosine monophosphate, co-authoring four papers in 1973 alone.

Personal life

Sutherland married Mildred Rice in 1937, the same year that he graduated from Washburn College. In 1944, during World War II, Sutherland was called into service as a battalion surgeon under General George S. Patton, and was later sent to Germany, where he served as a staff physician in a military hospital until 1945. He had two sons and a daughter with Mildred Rice.

In 1962, Sutherland divorced his first wife. A year later, when he became professor of physiology at Vanderbilt University, Sutherland married Claudia Sebeste Smith, the assistant dean at the university, and they were together for the remainder of Sutherland's life.

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#6268.

2362) Gerhard Herzberg

Gist:

Work

Our world consists of atoms that are assembled in molecules. During many chemical reactions, molecules are broken down into smaller parts, free radicals, that are quickly combined with other parts and form new molecules. Molecules absorb light of fixed wavelengths, and these light spectrums can be used with quantum mechanical calculations to figure out how different molecules are constructed. Gerhard Herzberg developed these methods, and during the 1950s and 1960s he mapped out the chemical structure of a great many free radicals.

Summary

Gerhard Herzberg (born Dec. 25, 1904, Hamburg, Ger.—died March 3, 1999, Ottawa, Ont., Can.) was a Canadian physicist and winner of the 1971 Nobel Prize for Chemistry for his work in determining the electronic structure and geometry of molecules, especially free radicals—groups of atoms that contain odd numbers of electrons. His work provided the foundation for molecular spectroscopy.

Herzberg became Privatdozent (unsalaried lecturer) at the Darmstadt Institute of Technology in 1930 but fled Nazi Germany in 1935 and obtained a position with the University of Saskatchewan. From 1945 to 1948 he worked at the University of Chicago’s Yerkes Observatory in Williams Bay, Wisconsin, after which he returned to Canada, where he joined the National Research Council, Ottawa.

Herzberg’s spectroscopic studies not only provided experimental results of prime importance to physical chemistry and quantum mechanics but also helped stimulate a resurgence of investigations into the chemical reactions of gases. He devoted much of his research to diatomic molecules, in particular the most common ones—hydrogen, oxygen, nitrogen, and carbon monoxide. He discovered the spectra of certain free radicals that are intermediate stages in numerous chemical reactions, and he was the first to identify the spectra of certain radicals in interstellar gas. Herzberg also contributed much spectrographic information on the atmospheres of the outer planets and the stars. His most important works are Atomspektren und Atomstruktur (1936; Atomic Spectra and Atomic Structure) and a long-standing reference work, the four-volume Molecular Spectra and Molecular Structure (1939–79).

Details

Gerhard Heinrich Friedrich Otto Julius Herzberg (December 25, 1904 – March 3, 1999) was a German-Canadian pioneering physicist and physical chemist, who won the Nobel Prize for Chemistry in 1971, "for his contributions to the knowledge of electronic structure and geometry of molecules, particularly free radicals". Herzberg's main work concerned atomic and molecular spectroscopy. He is well known for using these techniques that determine the structures of diatomic and polyatomic molecules, including free radicals which are difficult to investigate in any other way, and for the chemical analysis of astronomical objects. Herzberg served as Chancellor of Carleton University in Ottawa, Canada from 1973 to 1980.

Early life and family

Herzberg was born in Hamburg, Germany on December 25, 1904 to Albin H. Herzberg and Ella Biber. He had an older brother, Walter, who was born in January 1904. Herzberg started Vorschule (pre-school) late, after contracting measles. Gerhard and his family were atheists and kept this fact hidden. His father died in 1914, at 43 years of age, after having suffered from dropsy and complications due to an earlier heart condition. Herzberg graduated Vorschule shortly after his father's death. He married Luise Herzberg (née Oettinger), a spectroscopist and fellow researcher in 1929. (Luise Herzberg, died in 1971.)

Honours and awards

Herzberg's most significant award was the 1971 Nobel Prize in Chemistry, which he was awarded "for his contributions to the knowledge of electronic structure and geometry of molecules, particularly free radicals". During the presentation speech, it was noted that at the time of the award, Herzberg was "generally considered to be the world's foremost molecular spectroscopist."

Herzberg was honoured with memberships or fellowships by a very large number of scientific societies, received many awards and honorary degrees in different countries. The NSERC Gerhard Herzberg Canada Gold Medal for Science and Engineering, Canada's highest research award, was named in his honour in 2000. The Canadian Association of Physicists also has an annual award named in his honour. The Herzberg Institute of Astrophysics is named for him. He was made a member of the International Academy of Quantum Molecular Science. Asteroid 3316 Herzberg is named after him. In 1964 he was awarded the Frederic Ives Medal by the OSA. He was later named an Honorary Member of the Society. At Carleton University, there is a building named after him that belongs to the Physics and Mathematics/Statistics Departments, Herzberg Laboratories. Herzberg was elected a Fellow of the Royal Society (FRS) in 1951.

The main building of John Abbott College in Montreal is named after him. Carleton University named the Herzberg Laboratories building after him. A public park in the College Park neighbourhood of Saskatoon also bears his name.

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