What foods contain chromium, and how is it good for the body? What is Chrome Web Lab

Chromium is one of the minerals that the body needs in very small quantities. It is found in all living things: humans, animals and plants. The amount of chromium that humans and animals need is very small and is measured in micrograms. Hence, the mineral is called a trace element.

It is needed to maintain health and ensure the normal physiological functioning of body systems. It cannot be produced on its own and must come from food or supplements. Those who are active should be getting enough of this mineral to maintain increased energy levels and stay productive.

Chromium in the body and its significance

Chromium is a metal, the symbol for the designation Cr. It occupies 24th place in the periodic table. In nature, it occurs mainly in the form of chromium iron ore, which is the most stable form.

Chromium was first discovered in the Urals in lead ore and is mentioned in the works of M.V. Lomonosov in 1763. At the end of 1797, the French chemist L.N. Volknen isolated it as a metal.

The predominant form found in the body is trivalent chromium (Cr3 +).

The element also exists in a different form: hexavalent (Cr6 +). But such chromium, in contrast to trivalent, is a toxic industrial product and is considered mutagenic.

Chromium, despite its small amount, is recognized as one of the most important minerals in the body.

It is a key element in the metabolism of carbohydrates and proteins and promotes muscle tone. It stimulates the synthesis of cholesterol and fatty acids, which are essential for the functioning of the brain and other processes.

This mineral is especially important for glucose metabolism and maintaining blood sugar balance, known as glucose tolerance factor. True, the mechanism of action is not yet fully clear for scientists.

However, it is believed to promote cellular insulin uptake by helping to move insulin across cell membranes. The ability to stimulate the absorption of insulin has led some scientists to speculate that chromium plays an anabolic role in the body.

Some studies have noted that it may prevent coronary artery disease.

For postmenopausal women, doctors may recommend a chromium-rich diet or supplements. It slows down the loss of calcium and may prevent osteoporosis.

The benefits of chromium for the human body

The benefits and effects of chromium on the human body were first discussed only at the end of the 1950s.

Initial research suggests that chromium supplementation may improve glucose tolerance in patients with Turner syndrome. This disease is associated with glucose intolerance, when cells are less sensitive to the action of insulin when transporting glucose across cell membranes.

The main functions of chromium include:

Helps control stable blood sugar levels in both diabetics and those with abnormally low blood sugar levels;

Enhances the action of insulin, which is needed for the metabolism and storage of protein, carbohydrates and fats, as well as for the utilization of glucose and the production of energy;

Takes part in the metabolism of nucleic acids necessary for the construction of DNA;

Promotes the synthesis of cholesterol and fatty acids, which are needed for normal brain function and many other processes in the human body;

Helps lower high blood pressure.

Certain chromium supplements may be helpful in lowering LDL cholesterol and increasing HDL cholesterol.

Chromium deficiency in the body, causes and symptoms

The amount of chromium in the body is very low and is defined as trace. But even with such a small value, most people have a lack of it. The main reasons for the deficiency, scientists say, is the insufficient amount of chromium in soil and water, as well as methods of processing products in which most of it is removed.

The main symptoms of a deficiency are:

Insulin resistance or glucose intolerance, which affects insulin's ability to regulate blood sugar;

High blood sugar, which can lead to the development of type 2 diabetes in older people;

Increased blood insulin levels;

High cholesterol levels, which can cause an increased risk of heart disease;

High blood pressure.

However, severe deficits are very rare. The main symptom is weight loss or damage to the brain, which leads to inflammation of the brain or mild numbness, tingling and burning sensation in the hands and feet.

People with diabetes or heart disease who have been injured or severe stress, a higher chromium intake may be required. This in turn can lead to increased excretion of chromium from the body and an imbalance in blood sugar.

Calcium supplements, antacids, and certain other medications containing calcium carbonate can interfere with the absorption of chromium, which can also cause a deficiency in the body.

The elderly are most vulnerable to chromium deficiency.

What foods contain chromium

In many cases, most of the chromium in products is lost during refining. For example, chromium in whole grains is found primarily in the bran and germ. When the grains are ground into flour, the bran and germ are removed, resulting in their inevitable loss.

Trivalent chromium is contained in wide range products. However, most foods contain only small amounts (less than 2 micrograms per 100 grams). This can make it difficult to obtain an adequate value for this micronutrient.

The best source of chromium is brewer's yeast. But many people have difficulty digesting and absorbing them, which is accompanied by bloating and nausea.

Other good sources include:

Relatively good sources serve:

Whole grains

Brown rice;

Meat (turkey, chicken, beef);

Egg yolks;

Green bean;

Fresh onions;

Broccoli;

Potato;

Green pepper;

Romaine lettuce;

Ripe tomatoes;

Grape;

Oranges;

Wheat germ, basil, and some wines, especially reds, are good sources.

In other products, including fruits, vegetables, dairy products, chromium is present in trace amounts.

Up to 18 percent can be chromium in canned food stored in cans from of stainless steel... But this is a toxic form of this microelement.

Chromium Supplements

Supplementation of vitamins and minerals is vital for the proper functioning of the entire body. They work synergistically, i.e. for the effectiveness of any nutrient required, and sometimes reinforced by the presence of another. For this reason, it is always best to take a multivitamin that can provide the right balance of essential nutrients.

However, you must always remember that even the most best complex is never a substitute for a proper balanced diet.

The most common chromium additive is chromium picolinate. Other vitamin complexes may include chromium chloride, nicotinate, and chromium citrate.

All of these supplements are different from the trivalent chromium found in food. When taking them, you need to be careful not to exceed the recommended dose, which is 50-200 mcg per day, since chromium is toxic in high doses.

Fortunately, as mentioned above, chromium deficiency is very rare and usually does not require additional supplementation.

According to guidelines MR 2.3.1.2432-08 norms of physiological requirements for energy and nutrients for various groups of the population of the Russian Federation, approved by Rospotrebnadzor in December 2008, the average consumption of chromium ranges from 25 to 160 μg per day. Physiological need for adults it is 50 mcg per day, and for children - 11-35 mcg.

The average daily intake for an adult should be in the 30-100 mcg range. Upper maximum allowable limit document is not installed.

These are the minimum doses per day to prevent the development of a deficiency. For therapeutic purposes, it can increase depending on the disease, taking into account the toxic limit.

Chromium metabolism in the body

When chromium enters the human body, only about 2 percent is absorbed. The rest is excreted in faeces. A diet high in simple sugars increases urinary excretion.

The absorbed chromium is stored in the liver, spleen, soft tissues and bones. Its assimilation and absorption is influenced by vitamins B1, B2, B3, B6, C, E, amino acids and magnesium, potassium, zinc.

Excess chromium in the body

Research by scientists has not revealed any side effects from high consumption of chromium. Perhaps this is why the upper is not installed anywhere. allowable rate consumption.

However, people with kidney or liver disease may be more vulnerable and, as a precaution, should avoid consuming chromium in excess of the recommended doses.

Excess chromium can build up in tissues and decrease, rather than increase, the effectiveness of insulin.

An excess may be accompanied by:

Stomach irritation;

Heart palpitations;

Pallor or rash on the skin.

This is more common when taking dietary supplements with chromium. Cases of liver and kidney damage have been reported from overconsumption of chromium picolinate supplements. Other forms of chromium did not cause such problems. As a precaution, do not take very high doses of chromium picolinate or choose another form of supplement.

When the first signs of an overdose appear, you must stop taking them.

Chromium can lower blood sugar levels. Therefore, if you are taking medications that lower insulin or glucose levels, check with your doctor before taking a supplement with it. The dosage of the medication may need to be reduced to avoid too low blood sugar.

When you need an extra chrome intake

Chromium has long been of interest for its possible link to various health conditions. Among the most active areas of research on the effects of chromium on the body is the possibility of its additional intake with:

Intravenous feeding;

Type 2 diabetes;

Hypoglycemia;

Lipid metabolism disorders;

Losing weight.

Chromium deficiency impairs the body's ability to use glucose to meet its energy needs and increases insulin requirements. Therefore, it has been suggested that supplementation may help control type 2 diabetes and glucose and insulin responses in individuals at high risk of developing the disease. Unfortunately, the results of many studies on this topic are still contradictory and do not give an exact answer.

In some studies, chromium supplementation at a dose of 150-1000 mcg per day reduced total cholesterol, low-density lipoprotein and triglyceride levels in patients with high cholesterol or atherosclerosis. However, other studies have shown no beneficial effects. This may be due to the fact that scientists do not control the diet, which affects the level of lipids in the blood.

Several studies have shown that chromium supplements help with weight loss. But the results are not significant. It has been noted that taking bioadditives with this trace element reduces cravings for high-carbohydrate foods and regulates appetite.

Summing up, we can say that chromium is still important for the body and benefits. But his additional reception must be agreed with the doctor. Of course, it is best to get it with your diet, eating foods containing this element. No supplement can ever replace a balanced, healthy diet.

Chromium plays a crucial role in regulating blood sugar levels: it is part of the so-called glucose tolerance factor, which, along with insulin, helps to ensure that after a meal, the blood sugar level does not rise too quickly and does not drop again too quickly.

Do you have high blood sugar levels? Do you have high cholesterol or cataracts? Are you gaining weight? These symptoms are often the result of a lack of chromium in the body.

Chromium is undeniably central to sugar metabolism.

Although many years of practice have shown that limiting carbohydrate intake is the easiest, most reliable way general recovery, allowing you to bypass the disease side, the best remedy for her nutritional treatment is chromium.

To reduce insulin resistance

When taken regularly, this trace mineral has significant therapeutic effects on a range of health conditions that cause or exacerbate insulin resistance - including:

Overweight

In addition to switching to a low-carb diet, taking supplements with chrome — The best way that will reliably help you get rid of unwanted fat. Studies have shown that chromium acts in several directions:

• By reducing sugar cravings, chromium makes it easier to stick to a low-carb diet.
• Even without adherence, the mineral can increase the total musculoskeletal mass of the body, which, in turn, speeds up the metabolism and burns excess fat.
• Chromium helps prevent muscle loss if you deliberately limit calorie intake.
• The mineral promotes calorie burning during exercise, making it even easier to lose weight. Workout also increase emissions chrome from the body, increasing your need for supplementation.

To lower cholesterol levels

Turning on chrome in a nutritional supplement program helps raise blood levels of HDL-cholesterol, which cleans the arteries, while lowering LDL-cholesterol and triglyceride levels. The total cholesterol concentration also decreases.

The decrease is even more dramatic when a small amount of (niacin) is added to the chromium, the researchers report.

To relieve headaches and strengthen bones

Therapeutic value chrome in other areas it is not as well established as in cases of diabetes, cardiovascular disease and hypertension, but it can spread to many other diseases:

1. It may relieve chronic headaches and help treat acne, which, apparently, is partly due to impaired insulin metabolism.
2. Chromium strengthens bones by increasing levels of dehydroepiandrosterone (DHEA), and therefore may be part of the treatment program for osteoporosis.
3. Although we cannot say that chromium prevents glaucoma, it can (together with) restrain the growth of intraocular pressure.

The consequences of a deficit

More than 90% of Americans, for example, are deficient in chromium. And as often happens, least of all it is for those who need it most. Failure chrome has a self-sustaining character. When your body is low on this trace element, you are more drawn to sweets.

But the more sugar you eat, the more your reserves are depleted. chrome... Given that the average American consumes about 150 pounds (68 kg) of sugar and corn syrup each year these days, it should come as no surprise that insulin resistance and deficiency problems chrome have become so common.

If you have excess weight, it is very likely that you are insulin resistant. Obesity is both a cause and a consequence of this metabolic disorder. Insulin metabolism disorders and obesity are equal risk factors for heart disease.

Lack of chromium also increases the likelihood of developing heart disease.

Except for taking supplements, there is not enough good ways stock recovery chrome in organism.

True, mushrooms, barley and whole grains contain this trace element, but only if they are grown on a rich chrome soil. Seafood and meat are also considered good food sources, but again animals should be fed rich chrome diet.

National Research Tomsk Polytechnic University

Institute of Natural Resources Geoecology and Geochemistry

Chromium

By discipline:

Chemistry

Completed:

student of group 2G41 Tkacheva Anastasia Vladimirovna 10/29/2014

Checked:

teacher Stas Nikolay Fedorovich

Position in the periodic system

Chromium- an element of a side subgroup of the 6th group of the 4th period of the periodic system of chemical elements of D.I.Mendeleev with atomic number 24. It is designated by the symbol Cr(lat. Chromium). Simple substance chromium- solid metal, bluish-white. Chromium is sometimes referred to as ferrous metals.

Atom structure

17 Cl) 2) 8) 7 - diagram of the structure of the atom

1s2s2p3s3p- electronic formula

The atom is located in the III period, and has three energy levels

The atom is located in VII in the group, in the main subgroup - at the external energy level of 7 electrons

Element properties

Physical properties

Chromium is a white shiny metal with a cubic body-centered lattice, a = 0.28845 nm, characterized by hardness and brittleness, with a density of 7.2 g / cm 3, one of the hardest pure metals (second only to beryllium, tungsten and uranium), with a melting point of 1903 degrees. And with a boiling point of about 2570 degrees. C. In air, the surface of chromium is covered with an oxide film, which protects it from further oxidation. The addition of carbon to chromium further increases its hardness.

Chemical properties

Chromium under normal conditions is an inert metal; when heated, it becomes quite active.

Interaction with non-metals

When heated above 600 ° C, chromium burns out in oxygen:

4Cr + 3O 2 = 2Cr 2 O 3.

It reacts with fluorine at 350 ° С, with chlorine - at 300 ° С, with bromine - at the temperature of red heat, forming chromium (III) halides:

2Cr + 3Cl 2 = 2CrCl 3.

Reacts with nitrogen at temperatures above 1000 ° C with the formation of nitrides:

2Cr + N 2 = 2CrN

or 4Cr + N 2 = 2Cr 2 N.

2Cr + 3S = Cr 2 S 3.

Reacts with boron, carbon and silicon to form borides, carbides and silicides:

Cr + 2B = CrB 2 (formation of Cr 2 B, CrB, Cr 3 B 4, CrB 4 is possible),

2Cr + 3C = Cr 2 C 3 (formation of Cr 23 C 6, Cr 7 B 3 is possible),

Cr + 2Si = CrSi 2 (formation of Cr 3 Si, Cr 5 Si 3, CrSi is possible).

Does not directly interact with hydrogen.

Interaction with water

In a finely divided incandescent state, chromium reacts with water, forming chromium (III) oxide and hydrogen:

2Cr + 3H 2 O = Cr 2 O 3 + 3H 2

5interactions with acids

In the electrochemical series of metal voltages, chromium is up to hydrogen, it displaces hydrogen from solutions of non-oxidizing acids:

Cr + 2HCl = CrCl 2 + H 2;

Cr + H 2 SO 4 = CrSO 4 + H 2.

In the presence of atmospheric oxygen, chromium (III) salts are formed:

4Cr + 12HCl + 3O 2 = 4CrCl 3 + 6H 2 O.

Concentrated nitric and sulfuric acids passivate chromium. Chromium can dissolve in them only with strong heating, chromium (III) salts and acid reduction products are formed:

2Cr + 6H 2 SO 4 = Cr 2 (SO 4) 3 + 3SO 2 + 6H 2 O;

Cr + 6HNO 3 = Cr (NO 3) 3 + 3NO 2 + 3H 2 O.

Interaction with alkaline reagents

In aqueous solutions of alkalis, chromium does not dissolve, slowly reacts with alkali melts with the formation of chromites and the release of hydrogen:

2Cr + 6KOH = 2KCrO 2 + 2K 2 O + 3H 2.

Reacts with alkaline melts of oxidizing agents, for example potassium chlorate, while chromium is converted to potassium chromate:

Cr + KClO 3 + 2KOH = K 2 CrO 4 + KCl + H 2 O.

Recovery of metals from oxides and salts

Chromium is an active metal capable of displacing metals from solutions of their salts: 2Cr + 3CuCl 2 = 2CrCl 3 + 3Cu.

Properties of a simple substance

Stable in air due to passivation. For the same reason, it does not react with sulfuric and nitric acids. Burns at 2000 ° C with the formation of green chromium (III) oxide Cr 2 O 3, which has amphoteric properties.

Compounds of chromium with boron were synthesized (borides Cr 2 B, CrB, Cr 3 B 4, CrB 2, CrB 4 and Cr 5 B 3), with carbon (carbides Cr 23 C 6, Cr 7 C 3 and Cr 3 C 2), with silicon (silicides Cr 3 Si, Cr 5 Si 3 and CrSi) and nitrogen (nitrides CrN and Cr 2 N).

Cr compounds (+2)

The oxidation state +2 corresponds to the basic oxide CrO (black). Cr 2+ salts (blue solutions) are obtained by reduction of Cr 3+ salts or dichromates with zinc in an acidic medium (“with hydrogen at the time of isolation”):

All these Cr 2+ salts are strong reducing agents to the extent that they displace hydrogen from water upon standing. Oxygen in the air, especially in an acidic environment, oxidizes Cr 2+, as a result of which the blue solution quickly turns green.

Brown or yellow hydroxide Cr (OH) 2 precipitates when alkalis are added to solutions of chromium (II) salts.

Chromium dihalides CrF 2, CrCl 2, CrBr 2 and CrI 2 were synthesized

Cr (+3) compounds

The oxidation state +3 corresponds to amphoteric oxide Cr 2 O 3 and hydroxide Cr (OH) 3 (both are green). This is the most stable oxidation state of chromium. Chromium compounds in this oxidation state have a color from dirty lilac (ion 3+) to green (anions are present in the coordination sphere).

Cr 3+ tends to form double sulfates of the type M I Cr (SO 4) 2 12H 2 O (alum)

Chromium (III) hydroxide is obtained by acting with ammonia on solutions of chromium (III) salts:

Cr + 3NH + 3H2O → Cr (OH) ↓ + 3NH

You can use solutions of alkalis, but in their excess, a soluble hydroxo complex is formed:

Cr + 3OH → Cr (OH) ↓

Cr (OH) + 3OH →

By fusing Cr 2 O 3 with alkalis, chromites are obtained:

Cr2O3 + 2NaOH → 2NaCrO2 + H2O

Uncalcined chromium (III) oxide dissolves in alkaline solutions and acids:

Cr2O3 + 6HCl → 2CrCl3 + 3H2O

When chromium (III) compounds are oxidized in an alkaline medium, chromium (VI) compounds are formed:

2Na + 3HO → 2NaCrO + 2NaOH + 8HO

The same happens when chromium (III) oxide is fused with alkali and oxidizing agents, or with alkali in air (the melt thus acquires a yellow color):

2Cr2O3 + 8NaOH + 3O2 → 4Na2CrO4 + 4H2O

Chromium compounds (+4)[

With the careful decomposition of chromium (VI) oxide CrO 3 under hydrothermal conditions, chromium (IV) oxide CrO 2 is obtained, which is ferromagnetic and has metallic conductivity.

Among chromium tetrahalides, CrF 4 is stable, chromium tetrachloride CrCl 4 exists only in vapors.

Chromium compounds (+6)

The oxidation state +6 corresponds to the acidic chromium (VI) oxide CrO 3 and a number of acids, between which there is an equilibrium. The simplest of them are chromic H 2 CrO 4 and two-chromic H 2 Cr 2 O 7. They form two series of salts: yellow chromates and orange dichromates, respectively.

Chromium oxide (VI) CrO 3 is formed by the interaction of concentrated sulfuric acid with dichromate solutions. A typical acidic oxide, when interacting with water, it forms strong unstable chromic acids: chromic H 2 CrO 4, dichromic H 2 Cr 2 O 7 and other isopolyacids with the general formula H 2 Cr n O 3n + 1. An increase in the degree of polymerization occurs with a decrease in pH, that is, an increase in acidity.

Chromium is a refractory, very hard metal with extraordinary resistance to corrosion. These unique qualities have provided him with such a high demand in industry and construction.

The consumer is most often familiar not with chrome products, but with objects covered with a thin layer of metal. The dazzling mirror shine of such a coating is attractive in itself, but it also has a pure practical significance... Chromium is corrosion resistant and able to protect alloys and metals from rust.

And today we will answer the questions about whether chrome is a metal or a non-metal, and if it is a metal, then what kind: black or non-ferrous, heavy or light. We will also tell you in what form chromium is found in nature, and what are the differences between chromium and other similar metals.

First, let's talk about what chromium looks like, what are the metals containing it, and what is the peculiarity of such a substance. Chromium is a typical metal of a silvery-bluish color, heavy, surpasses in density, and also belongs to the category of refractory - its melting and boiling points are very high.

The chrome element is located in the side subgroup of the 6th group in the 4th period. It is similar in properties to molybdenum and tungsten, although it also has noticeable differences. The latter most often exhibit only the highest oxidation state, while chromium exhibits valences of two, three, and six. This means that the element forms many different compounds.

It was the compounds that gave the name to the element itself - from the Greek paint, color. The fact is that its salts and oxides are colored in a wide variety of bright colors.

This video will tell you about what chrome is:

Features and differences compared to other metals

When studying metal, two properties of the substance aroused the greatest interest: hardness and refractoriness. Chromium is one of the most hard metals- takes the fifth place and is inferior to uranium, iridium, tungsten and beryllium. However, this quality turned out to be unclaimed, since the properties of the metal were found to be more important for the industry.

Chromium melts at 1907 C. It is inferior to tungsten or molybdenum in this indicator, but still refers to refractory substances. However, impurities strongly influence its melting point.

• Like many of the metals that are resistant to corrosion, chromium forms a thin and very dense oxide film in air. The latter covers the access of oxygen, nitrogen and moisture to the substance, which makes it invulnerable. The peculiarity is that it transfers this quality to its alloy with: in the presence of the element, the potential of the a-phase of iron increases and, as a result, steel in air is also covered with a dense oxide film. This is the secret to the durability of stainless.
• Being a refractory substance, the metal also raises the melting point of the alloy. Heat-resistant and heat-resistant steels necessarily include a proportion of chromium, and sometimes very large - up to 60%. An even stronger effect is exerted by the addition of both, and chromium.
• Chromium also forms alloys with its brothers in the group - molybdenum and tungsten. They are used to coat parts where a particularly high wear resistance is required under high temperature conditions.

The pros and cons of chromium are described below.

Chromium as metal (photo)

Advantages

Like any other substance, metal has its own advantages and disadvantages, and their combination determines its use.

• The undoubted plus of the substance is its corrosion resistance and the ability to transfer this property to its alloys. Chrome stainless steels are of great importance as they solved a number of problems at once in the construction of ships, submarines, building frames and so on.
• Corrosion resistance is provided in another way - they cover the object with a thin layer of metal. The popularity of this method is very high, today there are at least a dozen methods of chrome plating in different conditions and to get different results.
• The chrome layer creates a bright mirror shine, so chrome plating is used not only to protect the alloy from corrosion, but also to obtain an aesthetic appearance... Moreover, modern methods of chrome plating make it possible to create a coating on any material - not only on metal, but also on plastic and ceramics.
• Obtaining heat-resistant steel with the addition of chromium should also be attributed to the advantages of the substance. There are many areas where metal parts must work at high temperatures, and iron itself does not have such resistance to stress at temperature.
• Of all the refractory substances, it is the most resistant to acids and bases.
• A plus of the substance can be considered its prevalence - 0.02% in the earth's crust, and a relatively simple method of extraction and production. Of course, it requires energy, but cannot be compared with a complex one, for example.

disadvantages

The disadvantages include qualities that do not allow full use of all the properties of chromium.

• First of all, it is a strong dependence of physical, and not only chemical properties from impurities. Even the melting point of the metal was difficult to establish, since in the presence of an insignificant fraction of nitrogen or carbon, the indicator changed noticeably.
• Despite the higher electrical conductivity compared to, chromium is used much less in electrical engineering and its cost is quite high. Making something out of it is much more difficult: heat melting and hardness markedly limits the application.
• Pure chromium is a malleable metal that contains impurities and becomes very hard. To obtain at least a relatively plastic metal, it has to be subjected to additional processing which, of course, increases manufacturing costs.

Metal structure

The chromium crystal has a body-centered cubic lattice, a = 0.28845 nm. Above a temperature of 1830 C, a modification with a face-centered cubic lattice can be obtained.

At a temperature of +38 C, a second-order phase transition with an increase in volume is recorded. In this case, the crystal lattice of the substance does not change, but its magnetic properties become completely different. Up to this temperature - the Neel point, chromium exhibits the properties of an antiferromagnet, that is, it is a substance that is almost impossible to magnetize. Above the Néel point, the metal becomes a typical paramagnet, that is, it exhibits magnetic properties in the presence of a magnetic field.

Properties and characteristics

Under normal conditions, the metal is quite inert - both due to the oxide film and simply by its nature. However, when the temperature rises, it reacts with simple substances, and with acids, and with bases. Its compounds are very diverse and widely used. The physical characteristics of the metal, as mentioned, are highly dependent on the amount of impurities. In practice, they deal with chromium with a purity of up to 99.5%. are as follows:

• melting temperature- 1907 C. This value serves as the boundary between refractory and ordinary substances;
• boiling temperature- 2671 C;
• Mohs hardness – 5;
• electrical conductivity- 9106 1 / (Ohm m). According to this indicator, chrome is second only to silver and gold;
• resistivity–127 (Ohm mm2) / m;
• thermal conductivity substance is 93.7 W / (m K);
• specific heat–45 J / (g K).

The thermophysical characteristics of the substance are somewhat anomalous. At the Neel point, where the volume of the metal changes, its coefficient thermal expansion increases sharply and continues to rise with increasing temperature. The thermal conductivity also behaves anomalously - it falls at the Neel point and decreases with heating.

The element is one of the necessary ones: in the human body, chromium ions are participants in carbohydrate metabolism and the process of regulating the release of insulin. The daily dose is 50-200 mcg.

Chromium is non-toxic, although in the form of a metal powder it can irritate the mucous membranes. Its trivalent compounds are also relatively safe and are even used in the food and sports industries. But hexavalent for humans are poison, cause severe damage to the respiratory tract and gastrointestinal tract.

Today we will talk about the production and price of chromium metal per kg further.

This video will show you if the finish is chrome:

Production

V a large number different minerals - often accompanies and. However, its content is insufficient to be of industrial importance. Only rocks containing at least 40% of the element are promising, therefore there are few minerals suitable for extraction, mainly chrome iron ore or chromite.

Mineral and quarrying methods are extracted depending on the depth of occurrence. And since the ore initially contains a large proportion of metal, it is practically never enriched, which, accordingly, simplifies and reduces the cost of the production process.

About 70% of the mined metal is used for alloying steel. Moreover, it is often used not in pure form, but in the form of ferrochrome. The latter can be obtained directly in a mine electric furnace or blast furnace - this is how carbon ferrochrome is obtained. If a compound with a low carbon content is required, resort to the aluminothermal method.

• This method produces both pure chromium and ferrochrome. To do this, a charge is loaded into the smelting shaft, including chromium iron ore, chromium oxide, sodium nitrate, etc. The first portion, the pilot mixture, is ignited, and the rest of the charge is loaded into the melt. At the end, add a flux - lime to facilitate the extraction of chromium. Melting takes about 20 minutes. After some cooling, the shaft is tilted, slag is released, returned to its original position and tilted again, now both chrome and slag are removed into the mold. After cooling, the resulting block is separated.
• Another method is also used - metallothermal melting. It is carried out in an electric furnace in a rotating shaft. The charge is divided here into 3 parts, each with a different composition. This method allows you to extract more chromium, but, most importantly, it reduces consumption.
• If it is required to obtain a chemically pure metal, they resort to the laboratory method: crystals are planted by electrolysis of chromate solutions.

The cost of chromium metal per 1 kg fluctuates markedly, since it depends on the volume of rolled metal produced - the main consumer of the element. In January 2017, 1 ton of metal was estimated at $ 7655.

Application

Categories

So, . The main consumer of chromium is ferrous metallurgy. This is due to the ability of the metal to transfer its properties such as corrosion resistance and hardness to its alloys. Moreover, it has an effect when added in very small quantities.

All chromium and iron alloys are divided into 2 categories:

• low-alloyed- with chromium content up to 1.6%. In this case, chromium adds strength and hardness to the steel. If the tensile strength of ordinary steel is 400-580 MPa, then the same steel grade with the addition of 1% of the substance will demonstrate a limit equal to 1000 MPa;
• highly alloyed- contain more than 12% chromium. Here, the metal provides the alloy with the same corrosion resistance as it does. All stainless steels are called chrome because it is this element that provides this quality.

Low-alloy steels are structural: they are used to make numerous machine parts - shafts, gear wheels, pushers, and so on. The scope of use of stainless steel is huge: metal parts of turbines, hulls of ships and submarines, combustion chambers, fasteners of any kind, pipes, channels, angles, sheet steel and so on.

In addition, chromium increases the temperature resistance of the alloy: with a substance content of 30 to 66%, heat-resistant steel products can perform their functions when heated to 1200 C. This is a material for piston engine valves, for fasteners, for turbine parts and others.

If 70% of chromium goes to the needs of metallurgy, then the remaining almost 30% is used for chromium plating. The essence of the process is to apply a thin layer of chromium to the surface of a metal object. A variety of methods are used for this, many are available to home craftsmen.

Chrome plating

Chrome plating can be divided into 2 categories:

• functional- its purpose is to prevent corrosion of the product. The layer thickness is greater here, so the chrome plating process takes longer - sometimes up to 24 hours. In addition to the fact that the chrome layer prevents rusting, it significantly increases the wear resistance of the part;
• decorative- chrome creates a mirror-shiny surface. Car enthusiasts and motorcycle racers rarely give up the opportunity to decorate their car with chrome parts. The decorative layer of the coating is much thinner - up to 0.0005 mm.

Chrome plating is actively used in modern construction and in the manufacture of furniture. Mirror-finish fittings, bathroom and kitchen accessories, kitchen utensils, furniture parts - chrome-plated products are extremely popular. And since thanks to modern method chrome plating, the coating can be created on literally any object, and several atypical methods of application have appeared. So, for example, chrome plumbing cannot be attributed to trivial solutions.

Chromium is a metal with very unusual properties, and its qualities are in demand in the industry. For the most part, its alloys and compounds are of interest, which only increases the value of the metal for the national economy.

The video below will tell you about removing chrome from metal:

Chromium (Cr), chemical element VI group of the periodic system of Mendeleev. Refers to a transition metal with atomic number 24 and atomic mass 51.996. Translated from Greek, the name of the metal means "color". The metal owes this name to a variety of colors, which is inherent in its various compounds.

Physical characteristics of chromium

The metal has sufficient hardness and brittleness at the same time. On the Mohs scale, the hardness of chromium is 5.5. This figure means that chromium has the highest hardness of all metals known today, after uranium, iridium, tungsten and beryllium. For the simple substance chromium, a bluish-white color is characteristic.

Metal is not a rare element. Its concentration in the earth's crust reaches 0.02% of the mass. shares. Chromium is never found in its pure form. It is found in minerals and ores, which are the main source of metal mining. Chromite (chromium iron ore, FeO * Cr 2 O 3) is considered the main compound of chromium. Another fairly common, but less important mineral is crocoite PbCrO 4.

The metal is easily melted at a temperature of 1907 0 C (2180 0 K or 3465 0 F). At a temperature of 2672 0 С - it boils. The atomic mass of the metal is 51.996 g / mol.

Chromium is a unique metal due to its magnetic properties. Antiferromagnetic ordering is inherent in it at room temperature, while other metals exhibit it at extremely low temperatures. However, if chromium is heated above 37 0 С, physical properties chromium changes. So, the electrical resistance and the coefficient of linear expansion change significantly, the elastic modulus reaches minimum value, and internal friction increases significantly. This phenomenon is associated with the passage of the Néel point, at which the antiferromagnetic properties of the material can change to paramagnetic. This means that the first level has been passed, and the substance has sharply increased in volume.

The structure of chromium is a body-centered lattice, due to which the metal is characterized by the temperature of the brittle-ductile period. However, in the case of this metal, the degree of purity is of great importance, therefore, the value is in the range -50 0 С - +350 0 С. As practice shows, the crystallized metal does not have any ductility, but soft annealing and molding make it malleable.

Chemical properties of chromium

The atom has the following external configuration: 3d 5 4s 1. As a rule, in compounds, chromium has the following oxidation states: +2, +3, +6, among which Cr 3+ exhibits the greatest stability. In addition, there are other compounds in which chromium exhibits a completely different oxidation state, namely: +1 , +4, +5.

The metal is not particularly reactive. While chromium is under normal conditions, the metal exhibits resistance to moisture and oxygen. However, this characteristic does not apply to the compound of chromium and fluorine - CrF 3, which, when exposed to temperatures exceeding 600 0 C, interacts with water vapor, forming as a result of the reaction Cr 2 O 3, as well as nitrogen, carbon and sulfur.

During the heating of metallic chromium, it interacts with halogens, sulfur, silicon, boron, carbon, and some other elements, resulting in the following chemical reactions chrome:

Cr + 2F 2 = CrF 4 (doped with CrF 5)

2Cr + 3Cl 2 = 2CrCl 3

2Cr + 3S = Cr 2 S 3

Chromates can be obtained by heating chromium with molten soda in air, nitrates or chlorates of alkali metals:

2Cr + 2Na 2 CO 3 + 3O 2 = 2Na 2 CrO 4 + 2CO 2.

Chromium has no toxicity, which cannot be said about some of its compounds. As you know, the dust of this metal, when it enters the body, can irritate the lungs, it is not absorbed through the skin. But, since it does not occur in its pure form, its entry into the human body is impossible.

Trivalent chromium enters environment during the mining and processing of chrome ore. The ingestion of chromium in the human body is likely in the form food additive used in weight loss programs. Chromium with a valency of +3 is an active participant in glucose synthesis. Scientists have found that excessive use of chromium does not cause much harm to the human body, since it is not absorbed, however, it is able to accumulate in the body.

Compounds in which a hexavalent metal is involved are extremely toxic. The likelihood of their entering the human body appears during the production of chromates, chrome plating of objects, during some welding works... The ingestion of such chromium into the body is fraught with serious consequences, since compounds in which a hexavalent element is present are strong oxidants. Therefore, it can cause bleeding in the stomach and intestines, sometimes with intestinal perforation. When such compounds get on the skin, strong chemical reactions occur in the form of burns, inflammation, and ulcers.

Depending on the quality of chromium, which must be obtained at the output, there are several methods of metal production: electrolysis of concentrated aqueous solutions of chromium oxide, electrolysis of sulfates, and reduction with silicon oxide. However, the latter method is not very popular, since it produces chromium with a huge amount of impurities in the output. Moreover, it is also economically disadvantageous.