MANGANESE CHEMICAL & PHYSICAL PROPERTIES - Ordinary manganese is a hard and brittle gray-white metal. It is chemically reactive and slowly decomposes in cold water. Manganese metal is ferromagnetic (only) after special treatment. Manganese is an important alloying agent. It is added to improve the strength, toughness, stiffness, hardness, wear resistance, and hardenability of steels. Together with aluminum and antimony, especially in the presence of copper, it forms highly ferromagnetic alloys. Manganese dioxide is used as a depolarizer in dry cells and as a decolorizing agent for glass that has been colored green due to iron impurities. The dioxide is also used in drying black paints and in the preparation of oxygen and chlorine.

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Manganese Facts

Manganese Chemical & Physical Properties

by Anne Marie Helmenstine, Ph.D. 

Manganese Basic Facts

Atomic Number: 25

Symbol: Mn

Atomic Weight: 54.93805

Discovery: Johann Gahn, Scheele, & Bergman 1774 (Sweden)

Electron Configuration: [Ar]4s² 3d⁵

Word Origin: Latin magnes: magnet, referring to the magnetic properties of pyrolusite; Italian manganese: corrupt form of magnesia

Properties: Manganese has a melting point of 1244+/-3°C, boiling point of 1962°C, specific gravity of 7.21 to 7.44 (depending on allotropic form), and valence of 1, 2, 3, 4, 6, or 7.

Ordinary manganese is a hard and brittle gray-white metal. It is chemically reactive and slowly decomposes in cold water.

Manganese metal is ferromagnetic (only) after special treatment.

There are four allotropic forms of manganese. The alpha form is stable at normal temperatures.

The gamma form changes to the alpha form at ordinary temperature. In contrast to the alpha form, the gamma form is soft, flexible, and easily cut.

Uses: Manganese is an important alloying agent. It is added to improve the strength, toughness, stiffness, hardness, wear resistance, and hardenability of steels.

Together with aluminum and antimony, especially in the presence of copper, it forms highly ferromagnetic alloys.

Manganese dioxide is used as a depolarizer in dry cells and as a decolorizing agent for glass that has been colored green due to iron impurities.

The dioxide is also used in drying black paints and in the preparation of oxygen and chlorine.

Manganese colors glass an amethyst color and is the coloring agent in natural amethyst.

The permanganate is used as an oxidizing agent and is useful for qualitative analysis and in medicine.

Manganese is an important trace element in nutrition, although exposure to the element is toxic in higher quantities.

Sources: In 1774, Gahn isolated manganese by reducing its dioxide with carbon.

The metal may also be obtained by electrolysis or by reducing the oxide with sodium, magnesium, or aluminum.

Manganese-containing minerals are widely distributed. Pyrolusite (MnO₂) and rhodochrosite (MnCO₃) are among the most common of these minerals.

Element Classification: Transition Metal

Isotopes: There are known 25 isotopes of manganese ranging from Mn-44 to Mn-67 and Mn-69.

The only stable isotope is Mn-55. The next most stable isotope is Mn-53 with a half-life of 3.74 x 10⁶ years. Density (g/cc): 7.21

Manganese Physical Data

Melting Point (K): 1517

Boiling Point (K): 2235

Appearance: Hard, brittle, grayish-white metal

Atomic Radius (pm): 135

Atomic Volume (cc/mol): 7.39

Covalent Radius (pm): 117

Ionic Radius: 46 (+7e) 80 (+2e)

Specific Heat (@20°C J/g mol): 0.477

Fusion Heat (kJ/mol): (13.4)

Evaporation Heat (kJ/mol): 221

Debye Temperature (K): 400.00

Pauling Negativity Number: 1.55

First Ionizing Energy (kJ/mol): 716.8

Oxidation States: 7, 6, 4, 3, 2, 0, -1 The most common oxidation states are 0, +2, +6 and +7

Lattice Structure: Cubic

Lattice Constant (Å): 8.890

CAS registry number: 7439-96-5

Manganese Trivia:

·      Manganese dioxide is used to make clear glass. Normal silica glass is tinted green and the manganese oxides add a purple tint to the glass that cancels out the green. Because of this property, glassmakers called it 'glassmaker's soap'.

·     Manganese is found in the enzymes necessary to metabolize fats and carbohydrates.

·     Manganese is found in the bones, liver, kidneys, and pancreas.

·     Manganese is important in the processes that form bones, clots blood, and regulates blood sugar.

·     As important as manganese is to our health, the body does not store manganese.

·     Manganese is the 12^th most abundant element in the Earth's crust.

·     Manganese has an abundance of 2 x 10^-4 mg/L in sea water (parts per million).

·     The permanganate ion (MnO₄^-) contains the +7 oxidation state of manganese.

·     Manganese was found in a black mineral called 'magnes' from the ancient Greek kingdom of Magnesia. Magnes was actually two different minerals, magnetite and pyrolusite. The pyrolusite mineral (manganese dioxide) was called 'magnesia'.

·     Manganese is used in steel production to fix the sulfur found in iron ores. It also strengthens steel and prevents oxidation.

References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.) International Atomic Energy Agency ENSDF database (Oct 2010)

Anne Marie Helmenstine, Ph.D.

Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

ThoughtCo and About Education chemistry expert since 2001.

Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor. 

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

ThoughtCo and Dotdash

ThoughtCo is a premier reference site focusing on expert-created education content. We are one of the top-10 information sites in the world as rated by comScore, a leading Internet measurement company. Every month, more than 13 million readers seek answers to their questions on ThoughtCo.

For more than 20 years, Dotdash brands have been helping people find answers, solve problems, and get inspired. We are one of the top-20 largest content publishers on the Internet according to comScore, and reach more than 30% of the U.S. population monthly. Our brands collectively have won more than 20 industry awards in the last year alone, and recently Dotdash was named Publisher of the Year by Digiday, a leading industry publication.

https://www.thoughtco.com/manganese-facts-606557

FLIGHT ATTENDANTS AND CANCER - Women and men on U.S. cabin crews have higher rates of many types of cancer, compared with the general population. This includes cancers of the breast, cervix, skin, thyroid and uterus, as well as gastrointestinal system cancers, which include colon, stomach, esophageal, liver and pancreatic cancers. One possible explanation for these increased rates is that flight attendants are exposed to a lot of known and potential carcinogens, or cancer-causing agents, within their work environment. One of those carcinogens is cosmic ionizing radiation, which is elevated at higher altitudes.

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Flight Attendants And Cancer

Why Cancer Rates Are Higher in Flight Attendants

By Cari Nierenberg 

This type of radiation is particularly damaging to DNA and is a known cause of breast cancer and nonmelanoma skin cancer, she said.

Air cabin crews receive the highest yearly dose of ionizing radiation on the job of all U.S. workers, she added.

In the new study, the researchers looked at data from more than 5,300 flight attendants from different airlines who completed an online survey as part of the Harvard Flight Attendant Health Study.

The analysis looked at the cancer rates in these flight attendants compared to a group of about 2,700 people who had a similar income and educational status but were not flight attendants.

The researchers found that in female flight attendants, the rates of breast cancer were about 50 percent higher than in women from the general population.

In addition, melanoma rates were more than two times higher and nonmelanoma skin cancer rates were about four times higher in female flight attendants compared with women from the general population. (Nonmelanoma skin cancers include basal cell and squamous cell carcinomas.)

These elevated cancer rates were observed despite indications of good-health behaviors, such as low levels of smoking and obesity, in the flight-attendant group as a whole, the study authors said.

Cancer rates in male flight attendants were nearly 50 percent higher for melanoma and about 10 percent higher for nonmelanoma skin cancers compared with men from the general population group, according to the findings.

Risks of very frequent flying

The potential cancer risks for flight attendants are not limited to cosmic ionizing radiation.

Cabin crew members are also regularly exposed to more UV radiation than the general population, which can make these workers more vulnerable to skin cancers, Mordukhovich said.

In addition, some studies have found that circadian rhythm disruptions, such as jet lag, might be linked with an increased risk of cancer, she said.

These disruptions could lead to changes in immune function and cell metabolism, which can reduce the suppression of tumors.

Another possible threat to the health of cabin crew members is chemical exposure, according to the study.

The women and men who worked as flight attendants prior to 1988, when smoking was first banned on some U.S. flights, were routinely exposed to secondhand smoke while on board the aircraft. 

Other chemical contaminants found in the cabin may include engine leakages, pesticides and flame retardants, which contain compounds that may act as hormone disruptors and increase the risk of some cancers, Mordukhovich said.

Further complicating matters is that flight attendants in the U.S. don't have the same occupational protections as their counterparts in the European Union.

There, exposure levels to radiation as well as work schedules are routinely monitored and adjusted to make sure flight attendants don't exceed certain guidelines for carcinogen exposure, Mordukhovich said.

There has been only limited research on the health of flight attendants, but they may not be the only air travelers to experience higher rates of cancer.

The rates may also be higher for pilots and people who fly often as passengers, Mordukhovich said.

Studies of pilots have generally shown higher rates of skin and prostate cancers, she noted, adding that pilots also have been found to have circadian rhythm disruption, but these workers have somewhat more built-in protections around their scheduling and rest times than flight attendants do.

Although the cancer risks for frequent flyers have not yet been studied, there is no reason to suspect these people would not have similar risks as those faced by cabin crews, Mordukhovich said.

Some limitations of the study are that researchers were not able to take into consideration individual UV exposures, such as sunbathing habits or leisure-time activities, which could influence skin cancer risk.

In addition, cancer rates were self-reported by study participants, and these diagnoses were not confirmed by a check of their medical records by the researchers, according to the study.

Cari Nierenberg, Live Science Contributor

https://www.livescience.com/62913-cancer-risk-flight-attendants.html

PROPYLENE GLYCOL - Propylene glycol is non-toxic in small amounts; however, large doses can cause seizures in humans and kidney and liver damage in animals. It dissolves food dyes and flavorings in drinks, and it keeps foods from freezing, such as in breweries and dairies. In cosmetics, PG is commonly used to emulsify oil components to water-based components. In medicines, PG acts as an emulsifier, specifically in topical agents and injectable medicines. It also acts as an excipient, or solvent, for the active ingredients in medications. Propylene glycol has a myriad of functions in industrial applications. The military uses it to form smoke screens for troops. Military and commercial airlines use it as a de-icer for planes, however, ethylene glycol is also used because of its lower cost.

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Propylene Glycol

What Is Propylene Glycol

By Chris Steel

Propylene glycol (PG) is a colorless and odorless liquid chemical used for decades in a wide array of applications.

A synthetic substance produced in industrial quantities, it is a relatively simple organic compound that has the chemical formula C3H8O2.

The U.S. Food and Drug Administration considers PG as non-toxic in small amounts; however, large doses can cause seizures in humans and kidney and liver damage in animals.

Food Additives

In foods, PG absorbs water and maintains moisture. It dissolves food dyes and flavorings in drinks, and it keeps foods from freezing, such as in breweries and dairies.

In food, it would be difficult to consume a dangerous dose, but babies, infants, the elderly and those with certain allergies may be more sensitive to the chemical.

Cosmetics

In cosmetics, PG is commonly used to emulsify oil components to water-based components.

Propylene glycol also helps cosmetic items keep from melting in high heat and freezing in low temperatures.

The small amounts used in cosmetics do not pose health risks, except to those with sensitivities.

Pharmaceuticals

In medicines, PG acts as an emulsifier, specifically in topical agents and injectable medicines. It also acts as an excipient, or solvent, for the active ingredients in medications.

Newborns have shown adverse reactions to medicines using this chemical.

Industrial Uses

Propylene glycol has a myriad of functions in industrial applications.

The textile industry uses it as an intermediary in the production of polyester fiber.

The military uses it to form smoke screens for troops.

Military and commercial airlines use it as a de-icer for planes, however, ethylene glycol is also used because of its lower cost.

PG can be found in liquid detergents, as well as a number of other uses.

Chris Steel began writing professionally in 2010, specializing in cooking, fitness and nutrition. He has also taught English for two years in Korea. Steel holds a bachelor's degree in sports sciences from Ohio University and an associate degree in culinary arts from Western Culinary Institute.

https://sciencing.com/what-propylene-glycol-5013190.html

USEFUL FACTS ABOUT IRON - Iron is an element that has been known in its pure form for at least 5,000 years. Iron is one of the most plentiful elements. It comprises about 5.6 percent of the Earth's crust and almost all of its core. The single largest use of iron is to make steel, an alloy of iron, and a smaller amount of carbon. Animals and plants require iron. Plants use iron in chlorophyll, the pigment used in photosynthesis. Humans use iron in hemoglobin molecules in blood to allow for the transport of oxygen to tissues throughout the body.

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Useful Facts About Iron

Interesting and Useful Facts about Iron

by Anne Marie Helmenstine, Ph.D. 

Iron is one of the elements you encounter in its pure form. It is essential for nutrition and used in a variety of household objects.

Here are some quick facts about iron.

Iron Facts

·          Iron is an element that has been known in its pure form for at least 5,000 years. The name "iron" comes from the Anglo-Saxon word "iron" and Scandinavian "iarn" for the metal.

·          The element symbol for iron is Fe, which comes from the Latin word for iron, "ferrum."

·         Iron is one of the most plentiful elements. It comprises about 5.6 percent of the Earth's crust and almost all of its core.

·          The single largest use of iron is to make steel, an alloy of iron, and a smaller amount of carbon. According to archaeological records from Anatolia — also called Asia Minor, a peninsula that today makes up the Asian part of Turkey — man has been producing steel for at least 4,000 years.

·          Iron is a transition metal.

·          Iron is not always magnetic. The a allotrope (or form) of iron is ferromagnetic, yet if it is transformed to the b allotrope, the magnetism disappears even though the crystal lattice is unchanged.

·         Animals and plants require iron. Plants use iron in chlorophyll, the pigment used in photosynthesis. Humans use iron in hemoglobin molecules in blood to allow for the transport of oxygen to tissues throughout the body.

·          Although iron is an essential mineral, much of it is extremely toxic. Free iron in the blood reacts with peroxides to form free radicals that damage DNA, protein, lipids and other cellular components, leading to illness and sometimes death. Twenty milligrams of iron per kilogram of body weight is toxic, while 60 milligrams per kilogram is lethal.

·         Iron primarily forms compounds with +2 and +3 oxidation states.

·         Iron is formed via fusion in stars that have sufficient mass. The sun and many other stars contain significant amounts of iron.

Anne Marie Helmenstine, Ph.D.

Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

ThoughtCo and About Education chemistry expert since 2001.

Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor. 

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

ThoughtCo and Dotdash

ThoughtCo is a premier reference site focusing on expert-created education content. We are one of the top-10 information sites in the world as rated by comScore, a leading Internet measurement company. Every month, more than 13 million readers seek answers to their questions on ThoughtCo.

For more than 20 years, Dotdash brands have been helping people find answers, solve problems, and get inspired. We are one of the top-20 largest content publishers on the Internet according to comScore, and reach more than 30% of the U.S. population monthly. Our brands collectively have won more than 20 industry awards in the last year alone, and recently Dotdash was named Publisher of the Year by Digiday, a leading industry publication.

https://www.thoughtco.com/interesting-iron-facts-606469