Manganese

Description

Not to be confused with magnesium , manganese is a trace mineral used by some people to help prevent bone loss and alleviate the bothersome symptoms associated with premenstrual syndrome (PMS). It may have a number of other beneficial effects as well. While most of the body's mineral content is composed of such macrominerals as calcium , magnesium, and potassium , certain trace minerals are also considered essential in very tiny amounts to maintain health and ensure proper functioning of the body. They usually act as coenzymes, working as a team with proteins to facilitate important chemical reactions. Even without taking manganese supplements, people with an average diet consume somewhere between 2 and 3 mg of the mineral through food and drink. While most authorities agree that manganese is a vital micronutrient, it is not known for certain if taking extra amounts can be helpful in treating osteoporosis , menstrual symptoms, or other problems.

Manganese, which is concentrated mainly in the liver, skeleton, pancreas, and brain, is considered important because it is used to make several key enzymes in the body and activates others. For example, one of the enzymes made from manganese is called superoxide dismutase (SOD), an antioxidant facilitator. Antioxidants help to protect cells from damage caused by free radicals, the destructive fragments of oxygen produced as a byproduct during normal metabolic processes. As these rogue particles travel through the body, they cause damage to cells and genes by stealing electrons from other molecules—a process referred to as oxidation. Manganese may also have some anticancer activity as well as a number of other important functions. It is believed to play a role in cholesterol and carbohydrate metabolism, thyroid function, blood sugar control, and the formation of bone, cartilage, and skin. While the effects of a manganese-free diet have not been thoroughly studied in people, animal experiments suggest that a lack of manganese can be unhealthy. Manganese deficiency in animals appears to have an adverse effect on the growth of bone and cartilage, brain function, blood sugar control, and reproduction. One recent study of dietary supplementation with manganese and other micronutrients in Mexican infants found that children who received the supplements grew faster and taller than a control group given a placebo. The authors concluded that growth retardation in children in developing countries is linked to manganese and other micronutrient deficiencies in the diet, among other factors.

General use

While considered necessary for general good health, manganese is also used for specific health concerns. Because of its role in maintaining strong bones, the mineral in combination with other trace minerals has been suggested as a possible treatment for osteoporosis. Manganese may also help to ease symptoms associated with menstrual periods and PMS. Getting adequate amounts of manganese may also be important for people with other diseases and health problems, from epilepsy and diabetes to rheumatoid arthritis , though this research is considered quite speculative.

The link between manganese and bone strength was examined in a double-blind, placebo-controlled trial published in the Journal of Nutrition in 1994, which studied the effects of minerals on preventing bone loss in 59 post-menopausal women in good health. The women were divided into several groups. Some of them received placebos, while others received calcium alone, trace minerals, or a combination of calcium and trace minerals. The trace minerals included manganese (5 mg a day), zinc (15 mg a day), and copper (2.5 mg a day). The study, which was conducted over a period of two years, found that calcium plus trace minerals was most effective in preventing bone loss in the spine. It was even more effective than calcium alone. This study shows the importance of taking calcium with these trace minerals in order to keep bones strong. Since manganese was studied in combination with other minerals, it is difficult to determine how big a factor it was in the study, or whether it must be taken with other minerals to produce benefits.

A small, double-blind study reported in the American Journal of Obstetrics and Gynecology in 1993 suggests that manganese and calcium may be a potent team in alleviating menstrual symptoms and PMS. Researchers from the Grand Forks Human Nutrition Research Center, which is affiliated with the U. S. Department of Agriculture, examined how calcium and manganese affect menstrual symptoms in women in good health. Ten women with normal menstrual cycles were studied for about 170 days. The women received 587 or 1,336 mg of calcium a day with 1.0 or 5.6 mg a day of manganese. They filled out a Menstrual Distress Questionnaire during each cycle and the results were analyzed. Getting more calcium improved mood, concentration, and behavior, and also reduced menstrual pain and the water retention associated with the premenstrual phase. The role of manganese appeared to be important. Despite getting higher amounts of calcium, women who received lower amounts of manganese experienced more moodiness and pain prior to their periods. This study suggests that getting adequate amounts of calcium and manganese can help to reduce the pain and other symptoms associated with menstrual periods.

Manganese may also be important for people with other diseases. Those with epilepsy, diabetes, and Perthes' disease tend to have low levels of the mineral, which has led to suggestions that manganese may help to prevent or treat these disorders. While sufficient research has not been conducted in humans to prove or discredit this theory, a handful of animal studies indicate that manganese may play a role in controlling seizures and blood sugar levels. Manganese may also decrease the risk of colon cancer by raising levels of the SOD enzyme, which has antioxidant effects.

Some people take manganese to help treat muscle strains or sprains, as well as rheumatoid arthritis, though there is no convincing scientific evidence to support these uses. Theoretically, manganese may act as an anti-inflammatory agent by boosting the activity of SOD.

Preparations

The optimum daily dosage of manganese has not been established with certainty. While there is no RDA or Daily Value (DV) for manganese, the U.S. government has established what is called an Estimated Safe and Adequate Dietary Intake (ESADDI). In adults and children age 11 and over, the ESADDI for manganese is 2–5 mg a day. Adequate intake for younger children varies with age. Daily dosage is 2–3 mg in youngsters aged seven to 10, 1.5–2.0 mg for those who are four to six, and 1.0–1.5 mg in children aged one to three. A pediatrician should be consulted to determine how much manganese is required in infants younger than one year of age.

Even without taking supplements, most women get about 2.2 mg a day of manganese through their diets , while men consume about 2.8 mg. Vegetarians and people who consume large amounts of whole-grain foods may get as much as 10–18 mg a day. Some authorities believe it is better for people to avoid manganese supplements altogether and increase their intake of foods known to contain significant amounts of the mineral. Manganese-rich foods and drinks include peanuts, pecans, pineapples and pineapple juice, shredded wheat and raisin bran cereals, and oatmeal. Other good sources include rice, sweet potatoes, spinach, whole wheat bread, and lima, pinto, and navy beans. Meat, poultry, fish, and dairy products are considered poor sources. Getting too much manganese through food and drink is not considered a significant risk because the mineral is present only in small amounts in plants and animals.

Some people take as much as 50–200 mg of manganese for several weeks to help treat muscle sprains or strains, but the safety and effectiveness of taking dosages this high are unknown.

Precautions

Manganese is not known to be harmful when taken in recommended dosages. Extremely high intake of the mineral, however, has resulted in cases of idiopathic Parkinson's disease . Recent studies indicate that high levels of manganese alter the blood-brain barrier, lowering the iron content of blood plasma while allowing the iron content of cerebrospinal fluid to rise. These cases of manganese-induced parkinsonism are usually limited to miners who inadvertently breath manganese-rich dust or people who drink contaminated water from wells. People who eat a manganese-rich diet are not considered at risk for these types of side effects. In fact, most foods high in manganese are believed to contribute to good health.

Side effects

When taken in recommended dosages, manganese is not associated with any bothersome or significant side effects.

Interactions

Manganese interacts with certain drugs and dietary supplements. People who take oral contraceptives or antacids may require higher intake of manganese. More of the mineral may also be needed in people who also take phosphorus , fiber, copper, iron, zinc, magnesium, or calcium.

Resources

BOOKS

Murray, Michael T. Encyclopedia of Nutritional Supplements. California: Prima Publishing, 1996.

PERIODICALS

Akram, M., C. Sullivan, and G. Mack, et al. "What is the Clinical Significance of Reduced Manganese and Zinc Levels in Treated Epileptic Patients?" Medical Journal of Australia (1989): 113.

Freeland-Graves, J. H., and J. R. Turnlund. "Deliberations and Evaluations of the Approaches, Endpoints and Paradigms for Manganese and Molybdenum Dietary Recommendations." Journal of Nutrition (1996): 2435S–2440S.

Penland, J. G., and P. E. Johnson. "Dietary Calcium and Manganese effects on Menstrual Cycle Symptoms." American Journal of Obstetrics and Gynecology (1993): 1417–23.

Rivera, Juan A., Teresita Gonzalez-Cossio, Mario Flores, et al. "Multiple Micronutrient Supplementation increases the Growth of Mexican Infants." American Journal of Clinical Nutrition 74 (November 2001): 657.

Strause, L, P. Saltman, and K. T. Smith, et al. "Spinal Bone Loss in Postmenopausal Women Supplemented with Calcium and Trace Minerals." Journal of Nutrition (1994): 1060–1064.

Zheng, Wei. "Neurotoxicity of the Brain Barrier System: New Implications." Journal of Toxicology: Clinical Toxicology 39 (December 2001): 711–720.

ORGANIZATIONS

NIH Osteoporosis and Related Bone Diseases National Resource Center. 1232 22nd St. NW, Washington, DC 20037-1292.

OTHER

American Society for Nutritional Sciences. <http://www.nutrition.org>.

Discovery Health. <http://www.discoveryhealth.com>.

Greg Annussek

Rebecca J. Frey, PhD

Manganese

Definition

Purpose

Description

Precautions

Interactions

Complications

Parental concerns

Resources

Definition

Manganese (Mn) is a mineral necessary in very tiny (trace) amounts for human health. In large quantities, manganese is poisonous. Manganese is used in some enzyme reactions and for the proper development of bones and cartilage. Humans must meet their needs for manganese from their diet. Manganese is

Manganese

(Illustration by GGS Information Services/Thomson Gale.)

found mainly in plants and in small quantities in some drinking water.

Purpose

Researchers understand less about how manganese functions in the body than they do about many other minerals. Studies have shown that manganese is necessary for proper development of healthy bones and cartilage in animals. It is highly likely that manganese plays the same role in the development of human bones and connective tissue, although manganese deficiency is so rare in humans (and putting people on a prolonged manganese-free diet would be an unethical experiment) that this has not been proven experimentally.

Manganese is also necessary for the formation of an antioxidant enzyme in cellular mitochondria. Mitochondria, sometimes called the cell’s power plant, are organelles that use large amounts of oxygen to produce energy. The production of energy by the mitochondria results in the formation of free radicals. Free radicals are molecules that cause damage by reacting with fats and proteins in cell membranes and in genetic material. This process is called oxidation. Antioxi-dants are compounds that attach themselves to free radicals so that it is impossible for free radicals to react with, or oxidize, other molecules. In this way, antiox-idants protect cells from damage. Although manganese is not by itself an antioxidant, it is a necessary part of the enzyme reaction that neutralizes free radicals produced by mitochondria. Manganese is also needed in some enzyme reactions that allow the body to process the use of amino acids, cholesterol, and carbohydrates in the body.

Description

Manganese is acquired through diet. It is not evenly distributed in the body but is concentrated in the bones, liver, pancreas, and brain. Excess manganese is removed in bile, a digestive fluid made by the liver. The role of manganese in health is not well understood. Both manganese deficiency and manganese excess are rare. The few cases of dietary manganese excess that have been recorded have resulted from accidental exposure such as from drinking water contaminated with manganese-containing industrial waste. The United States Environmental Protection Agency (EPA) recommends a concentration of manganese no higher than .05 mg/L in drinking water. Side effects of high levels of manganese include loss of appetite, headaches, tremors, convulsions, and mental changes such a hallucinations. If manganese is inhaled in dust or vapor, it can cause severe damage to the nervous system. Some miners and industrial workers are at risk of being exposed to airborne manganese.

Normal manganese requirements

The United States Institute of Medicine (IOM ) of the National Academy of Sciences has developed values called Dietary Reference Intakes (DRI s) for many vitamins and minerals. The DRI s consist of three sets of numbers. The Recommended Dietary Allowance (RDA ) defines the average daily amount of the nutrient needed to meet the health needs of 97–98% of the population. The Adequate Intake (AI ) is an estimate set when there is not enough information to determinean RDA. The Tolerable Upper Intake Level (UL ) is the average maximum amount that can be taken daily without risking negative side effects. The DRIs are calculated for children, adult men, adult women, pregnant women, and breastfeeding women.

The IOM has not set RDA s for manganese because not enough information is available about the need for manganese in humans. Instead, it has set AI levels for all age groups. Because high levels of manganese affect the nervous system, the ULs are very conservative. Some experts point out that vegans and vegetarians who eat large quantities of whole grains routinely take in manganese in amounts well above the established UL without any obvious adverse effects. IA s and UL s for manganese are measured in milligrams (mg).

The following list gives the daily IA s and UL s for manganese for healthy individuals as established by the IOM.

• children birth–6 months: AI 0.3 mg; UL not established; All manganese should come from food.
• children 7–12 months: AI 0.6 mg; UL not established; All manganese should come from food.
• children 1–3 years: RDA 1.2 mg; UL 2 mg
• children 4–8 years: RDA 1.5 mg; UL 3 mg
• boys 9–13 years: RDA 1.9 mg; UL 6 mg
• girls 9–13 years: RDA 1.6 mg; UL 6 mg
• boys 14–18 years: RDA 2.2 mg; UL 9 mg
• girls 14–18 years: RDA 1.6 mg; UL 9 mg
• children 4–8 years: RDA 1.5 mg; UL 3 mg
• boys 9–13 years: RDA 1.9 mg; UL 6 mg
• girls 9–13 years: RDA 1.6 mg; UL 6 mg
• boys 14–18 years: RDA 2.2 mg; UL 9 mg
• girls 14–18 years: RDA 1.6 mg; UL 9 mg
• men age 19 and older: RDA 2.3 mg; UL 11 mg
• women age 19 and older: RDA 1.8 mg; UL 11 mg
• pregnant women of all ages: RDA 2.0 mg; UL 11 mg
• breastfeeding women of all ages: RDA 2.6 mg; UL 11 mg

Sources of manganese

Almost all people get enough manganese from their normal diet. Good sources of manganese include nuts, seeds, whole grains, leafy green vegetables, and tea. Some water that is high in minerals (“hard” water) may contain small amounts of manganese; the amount varies depending on location. Whole grains contain manganese, but processing removes most of it. Therefore brown rice is a good source of manganese, but white rice is not. Whole wheat flour has more manganese than white flour, and wheat bran has more than either type of flour. Manganese is also found in multi-vitamin/mineral supplements, and in single-ingredient supplements. Joint supplements that contain glucosamine and chrondroitin may also contain manganese. The best way to get an adequate amount of manganese

KEY TERMS

Alternative medicine —A system of healing that rejects conventional, pharmaceutical-based medicine and replaces it with the use of dietary supplements and therapies such as herbs, vitamins, minerals, massage, and cleansing diets. Alternative medicine includes well-established treatment systems such as homeopathy, Traditional Chinese Medicine, and Ayurvedic medicine, as well as more-recent, fad-driven treatments.

Amino acid —Molecules that are the basic building blocks of proteins.

Antioxidant —A molecule that prevents oxidation. In the body antioxidants attach to other molecules called free radicals and prevent the free radicals from causing damage to cell walls, DNA, and other parts of the cell.

Bile —A greenish-yellow digestive fluid produced by the liver and stored in the gall bladder. It is released into the intestine where it helps digest fat, and then is removed from the body in feces.

Conventional medicine —Mainstream or Western pharmaceutical-based medicine practiced by medical doctors, doctors of osteopathy, and other licensed health care professionals.

Dietary supplement —A product, such as a vitamin, mineral, herb, amino acid, or enzyme, that is intended to be consumed in addition to an individual’s diet with the expectation that it will improve health.

Enzyme —A protein that change the rate of a chemical reaction within the body without themselves being used up in the reaction.

Free radical —A molecule with an unpaired electron that has a strong tendency to react with other molecules in DNA (genetic material), proteins, and lipids (fats), resulting in damage to cells. Free radicals are neutralized by antioxidants.

Glucose —A simple sugar that results from the breakdown of carbohydrates. Glucose circulates in the blood and is the main source of energy for the body.

Homeostasis —The complex set of regulatory mechanisms that works to keep the body at optimal physiological and chemical stability in order for cellular reactions to occur.

Hormone —A chemical messenger that is produced by one type of cell and travels through the bloodstream to change the metabolism of a different type of cell.

Mineral —An inorganic substance found in the earth that is necessary in small quantities for the body to maintain a health. Examples: zinc, copper, iron.

Osteoporosis —A condition found in older individuals in which bones decrease in density and become fragile and more likely to break. It can be caused by lack of vitamin D and/or calcium in the diet.

Serum —The clear fluid part of the blood that remains after clotting. Serum contains no blood cells or clotting proteins, but does contain electrolytes.

is to eat a healthy diet high in green vegetables and whole grains.

The following list gives the approximate manganese content for some common foods:

• raisin bran cereal, ½ cup: 0.94 mg
• brown rice, cooked, ½ cup: 0.88 mg
• pinto beans, cooked, ½ cup: 0.48 mg
• lima beans, cooked, ½ cup: 0.48 mg
• navy beans, cooked, ½ cup: 0.51 mg
• whole wheat bread, 1 slice: 0.65 mg
• pineapple, raw, ½ cup: 1.28 mg
• pecans, 1ounce: 1.12mg
• almonds, 1 ounce: 0.74 mg
• peanuts, 1 ounce: 0.59 mg
• spinach, cooked, ½ cup: 0.84 mg
• sweet potato, mashed, ½ cup: 0.55 mg
• tea, green, 1 cup (8 ounces): 0.40-1.58 mg
• tea, black, 1 cup (8 ounces): 0.18-0.77 mg

Controversial health claims for manganese

Manganese supplements have not been proven effective in treating or preventing any specific disease or condition. However, based on a small number of laboratory and animal studies, practitioners of alternative medicine sometimes recommend supplemental manganese for the following conditions. These uses are considered speculative by practitioners of conventional medicine.

• prevention of osteoporosis
• treatment of rheumatoid arthritis
• treatment of premenstrual symptoms

• seizure prevention in individuals with epilepsy
• control of glucose levels in people with diabetes

Precautions

Liver damage may reduce the rate at which magnesium is removed from the body. People with liver damage (e.g. cirrhosis) may be at higher risk of developing symptoms of manganese excess.

Interactions

Antacids and laxatives that contain magnesium (e.g. milk of magnesia) may reduce the amount of manganese absorbed from food.

Complications

No complications are expected from manganese acquired through food and water. Individuals who take multivitamin/mineral supplements containing manganese are unlikely to have any adverse effects. People who take manganese or joint supplements should be alert to how much manganese they are consuming, although overdose is extremely rare.

Parental concerns

Parental concerns

Parents should have few concerns about children getting either too much or too little manganese. Supplemental manganese should rarely be necessary. Parents should encourage their children to eat a diet high in fruits, vegetables, and whole grains.

Resources

BOOKS

Fragakis, Allison. The Health Professional’s Guide to Popular Dietary Supplements.Chicago: American Dietetic Association, 2003

Lieberman, Shari and Nancy Bruning. The Real Vitamin and Mineral Book: The Definitive Guide to Designing Your Personal Supplement Program,4th ed. New York: Avery, 2007.

Pressman, Alan H. and Sheila Buff. The Complete Idiot’s Guide to Vitamins and Minerals, 3rd ed. Indianapolis, IN: Alpha Books, 2007.

ORGANIZATIONS

Linus Pauling Institute. Oregon State University, 571 Weniger Hall, Corvallis, OR 97331-6512. Telephone: (541) 717-5075. Fax: (541) 737-5077. Website: <http://lpi.oregonstate.edu>

Office of Dietary Supplements, National Institutes of Health. 6100 Executive Blvd., Room 3B01, MSC 7517, Bethesda, MD 20892-7517 Telephone: (301)435-2920. Fax: (301)480-1845. Website: <http://dietary-supplements.info.nih.gov>

OTHER

Familydoctor.org. “Vitamins and Minerals: What You Should Know.” American Family Physician, December 2006. <http://familydoctor.org/>

Higdon, Jane. “Manganese.” Linus Pauling Institute-Oregon State University, August 8, 2001. <http://lpi.oregonstate.edu/infocenter/minerals/manganese>

Maryland Medical Center Programs Center for Integrative Medicine. “Manganese.” University of Maryland Medical Center, April 2002. <http://www.umm.edu/altmed/ConsSupplements/manganesecs>

Mayo Clinic Staff. “Dietary Supplements: Using Vitamin and Mineral Supplements Wisely.” MayoClinic.com, June 5, 2006. <http://www.mayoclinic.com/health/supplements/NU00198>

Helen M. Davidson

MANGANESE (REVISED)

Note: This article, originally published in 1998, was updated in 2006 for the eBook edition.

Overview

Manganese is a transition metal. The transition metals are the large block of elements in the middle of the periodic table. The periodic table is a chart that shows how chemical elements are related to each other. The transition metals make up Rows 4 through 7 in Groups 3 through 12 of the periodic table. Many of the best known and most widely used metals are in this group of elements.

It took chemists some time to discover the difference between manganese and iron. The two metals have very similar properties and often occur together in the Earth's crust. The first person to clearly identify the differences between the two elements was Swedish mineralogist Johann Gottlieb Gahn (1745-1818) in 1774.

SYMBOL
Mn

ATOMIC NUMBER
25

ATOMIC MASS
54.9380

FAMILY
Group 7 (VIIB)
Transition metal

PRONUNCIATION
MANG-guh-neez

Manganese plays an interesting role in the U.S. economy. It is absolutely essential in the production of iron and steel. No element has been found that can replace manganese is such applications. The United States has essentially no manganese supplies of its own, so it depends on imports from other nations.

Discovery and naming

One of the main ores of manganese is pyrolusite. Pyrolusite is made up primarily of the compound manganese dioxide (MnO₂). Early artists were familiar with pyrolusite. They used the mineral to give glass a beautiful purple color. They also used the mineral to remove color from a glass. When glass is made, it often contains impurities that give the glass an unwanted color. The presence of iron, for example, can give glass a yellowish tint. Adding pyrolusite to yellowish glass removes the color. The purple tint of pyrolusite balances out the yellow color of the glass. The glass ends up being clear and colorless.

By the mid-1700s, chemists began to suspect that pyrolusite might contain a new element. Some authorities credit German chemist Ignatius Gottfried Kaim with isolating the element in 1770. However, Kaim's report was not read by many chemists and was quickly lost.

During this period, some of the most famous chemists in Europe were trying to analyze pyrolusite, but none of them was successful. The problem was solved in 1774 when Gahn developed a method for removing the new element from pyrolusite. He heated pyrolusite with charcoal (pure carbon ). The carbon took oxygen away from manganese dioxide, leaving behind pure manganese:

The origin of manganese's name is a bit confusing. Early chemists associated the new element with a mineral called magnesia. That mineral got its name because it is magnetic. Magnesia does not contain manganese, but the name stuck.

Physical properties

Manganese is a steel-gray, hard, shiny, brittle metal. It is so brittle, in fact, that it cannot be machined in its pure form. Machining refers to the bending, cutting, and shaping of a metal by mechanical means. The melting point of manganese is 1,245°C (2,273°F) and its boiling point is about 2,100°C (3,800°F). Its density is 7.47 grams per cubic centimeter.

Manganese exists in four allotropic forms. Allotropes are forms of an element with different physical and chemical properties. The element changes from one form to another as the temperature rises. The form that exists from room temperature up to about 700°C (1,300°F) is the most common form.

Chemical properties

Manganese is a moderately active metal. It combines slowly with oxygen in the air to form manganese dioxide (MnO₂). At higher temperatures, it reacts more rapidly. It may even burn, giving off a bright white light. Manganese reacts slowly with cold water, but more rapidly with hot water or steam. It dissolves in most acids with the release of hydrogen gas. It also combines with fluorine and chloride to make manganese difluoride (MnF₂) and manganese dichloride (MnCl₂).

Occurrence in nature

Manganese never occurs as a pure element in nature. It always combines with oxygen or other elements. The most common ores of manganese are pyrolusite, manganite, psilomelane, and rhodochrosite. Manganese is also found mixed with iron ores. The largest producers of manganese ore in the world are China, South Africa, the Ukraine, Brazil, Australia, Gabon, and Kazakstan.

Manganese also occurs abundantly on the ocean floor in the form of nodules. These nodules are fairly large lumps of metallic ores. They usually contain cobalt, nickel, copper, and iron, as well as manganese. Scientists estimate that up to 1.5 trillion metric tons of manganese nodules may lie on the floors of the world's oceans and large lakes. Currently, there is no profitable method for removing these ores.

Manganese is the 12th most abundant element in the Earth's crust. Its abundance is estimated to be 0.085 to 0.10 percent. That makes it about as abundant as fluorine or phosphorus.

Up to 1.5 trillion metric tons of manganese nodules (large lumps of metallic ores) may lie on ocean floors.

Isotopes

Only one naturally occurring isotope of manganese exists, manganese-22. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope.

Nine radioactive isotopes of manganese are known also. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive.

None of the radioactive isotopes of manganese has any important commercial uses.

Extraction

The usual method for producing pure manganese is to heat manganese dioxide (MnO₂) with carbon or aluminum. These elements remove the oxygen and leave pure metal:

Uses

Up to 90 percent of all manganese produced is made into steel alloys. An alloy is made by melting and mixing two or more metals. The mixture has properties different from those of the individual metals. The addition of manganese to steel makes the final product hard, as well as resistant to corrosion (rusting) and mechanical shock.

The most common alloy of manganese is ferromanganese. This alloy contains about 48 percent manganese combined with iron and carbon. Ferromanganese is the starting material for making a very large variety of steel products, including tools, heavy-duty machinery, railroad tracks, bank vaults, construction components, and automotive parts. About 60 percent of the manganese used in the United States in 1996 went to the manufacture of ferromanganese.

Another common alloy of manganese is silicomanganese. It contains manganese, silicon, and carbon in addition to iron. It is used for structural components and in springs. The production of silicomanganese accounted for about 33 percent of the manganese used in the United States in 1996.

Manganese is also used to make alloys with metals other than iron or steel. For example, the alloy known as manganin is 84 percent copper, 12 percent manganese, and 4 percent nickel. Manganin is used in electrical instruments.

Compounds

Less than 10 percent of all the manganese used in the United States goes to the production of manganese compounds. Perhaps the most important commercial use of these compounds is manganese dioxide (MnO₂). Manganese dioxide is used to make dry-cell batteries. These batteries are used in electronic equipment, flashlights, and pagers. Dry cell batteries hold a black pasty substance containing manganese dioxide. The use of manganese dioxide in a dry cell prevents hydrogen gas from collecting in the battery as electricity is produced.

Another manganese compound, manganous chloride (MnCl₂), is an additive in animal food for cows, horses, goats, and other domestic animals. Fertilizers also contain manganous chloride so that plants get all the manganese they need.

Finally, small amounts of manganese compounds are used as coloring agents in bricks, textiles, paints, inks, glass, and ceramics. Manganese compounds can be found in shades of pink, rose, red, yellow, green, purple, and brown.

Health effects

Manganese is one of the chemical elements that has both positive and negative effects on living organisms. A very small amount of the element is needed to maintain good health in plants and animals. The manganese is used by enzymes in an organism. An enzyme is a molecule that makes chemical reactions occur more quickly in cells. Enzymes are necessary to keep any cell operating properly. If manganese is missing from the diet, enzymes do not operate efficiently. Cells begin to die, and the organism becomes ill.

Fortunately, the amount of manganese needed by organisms is very small. It is not necessary to take extra manganese to meet the needs of cells.

Manganous chloride (MnCl₂) is an additive in animal food.

In fact, an excess of manganese can create health problems. These problems include weakness, sleepiness, tiredness, emotional disturbances, and even paralysis. The only way to receive such a large dose is in a factory or mine. Workers may inhale manganese dust in the air.

Manganese

melting point: 1,246 ±3°C
boiling point: 2,061°C
density: 7.21–7.44 g/cm³ , depending upon allotrope
most common ions: Mn²⁺ , Mn³⁺ , MnO₄³⁻ , MnO₄²⁻ , MnO₄⁻

Manganese is a hard, brittle, gray-white metal in group 7B of the Periodic Table. It was recognized as an element in 1774 by Swedish chemist Carl Wilhelm Scheele and isolated by his assistant Johan Gottlieb Gahn later that year. The element's name is derived from the Latin word magnes, meaning "magnet." This refers to the magnetic property of the common ore pyrolusite.

Manganese is the twelfth most abundant transition element (1,060 parts per million of Earth's crust) with twenty-three known isotopes . Large nodules of manganese ore have been discovered on the ocean floor. The pure metal can be obtained by reduction of the oxide with sodium or by electrolysis.

Manganese is more reactive that any of its neighbors on the Periodic Table. It reacts with water to produce hydrogen gas and dissolves in dilute acids to form Mn²⁺. The most stable oxidation state of manganese is +2. The most important oxide formed is MnO₂, which decomposes to Mn₂O₃ if heated above 530°C (932°F). The deep-purple manganate (VII) salts (permanganates) are prepared in aqueous solution by oxidation of Mn²⁺.

Manganese metal is used in many alloys . In conjunction with aluminum and copper it forms strong ferromagnetic alloys. Ninety-five percent of all manganese ores are used in the production of steel. The element improves the strength and toughness of steel by acting as a scavenger of sulfur, preventing the formation of FeS, which induces brittleness. Biologically, manganese is an important trace element ; it is essential to the utilization of vitamin B¹. Pyrolusite has been used in glassmaking since ancient Egypt, while MnO₂ is used in the manufacture of dry cells. The permanganate ion is a strong oxidizing agent and is used in quantitative analysis and medicine.

see also Coordination Compounds; Inorganic Chemistry; Scheele, Carl.

Catherine H. Banks

Bibliography

Greenwood, Norman N., and Earnshaw, A. (1997). Chemistry of the Elements, 2nd edition. Boston: Butterworth-Heinemann.

Lide, David R., ed. (2003). "Manganese." In The CRC Handbook of Chemistry and Physics, 84th edition. Boca Raton, FL: CRC Press.

Internet Resources

"Manganese." U.S. Geological Survey, Mineral Commodity Summaries. Updated January 2003. Available from <http://minerals.usgs.gov/minerals/pubs/commodity/manganese/420303.pdf>.

man·ga·nese / ˈmanggəˌnēz; -ˌnēs/ • n. the chemical element of atomic number 25, a hard gray metal of the transition series. Manganese is an important component of special steels and magnetic alloys. (Symbol: Mn) ∎  the black dioxide of this as an industrial raw material or additive, esp. in glassmaking.