Chemical element chrome belongs to the VI group of a periodic system, it represents heavy, solid and refractory metal of bluish and steel color. Pure chrome is plastic, it is possible to find 4 its in the nature stable isotope, 6 radioactive were received by an artificial way.
Instruction
1. Chrome forms the interspersed massive ores in the ultramain rocks, this chemical element is more characteristic of an Earth's mantle. It is metal of deep zones of our planet, it also enriched stone meteorites.
2. More than 20 minerals of chrome are known, however only hromshpinelida have industrial value. In addition, chrome contains in a number of the minerals accompanying chrome ores, but they are not of practical value.
3. Chrome is a part of fabrics of plants and animals, in leaves he is present at a type of a low-molecular complex, and in an organism of animals participates in exchange of proteins, lipids and carbohydrates. The lowered chrome content in food leads to reduction of growth rate and decrease in sensitivity of peripheral fabrics.
4. Chrome crystallizes in a body-centered lattice. At a temperature about 1830 °C its transformation into modification with a face-centered lattice is possible. This element chemically maloaktiven, chrome is resistant to oxygen and moisture under usual conditions.
5. Interaction of chrome with oxygen proceeds actively in the beginning, then sharply slows down because of formation of an oxide film on the surface of metal. The film collapses at 1200 °C then oxidation begins to take place quickly. At a temperature about 2000 °C chrome lights up, forming dark green oxide.
6. Chrome easily reacts with the diluted solutions of sulfuric and hydrochloric acids, so receive sulfate and chloride of chrome, at the same time hydrogen is emitted. This metal forms a set of salts with oxygen-containing acids. Chromic acids and their salts are strong oxidizers.
7. As raw materials for receiving chrome serve hromshpinelida, they are subjected to enrichment then alloy with a potassium carbonate in the presence of air oxygen. The chromate of potassium which is formed at the same time is leached hot water under the influence of sulfuric acid, turning it into a bichromate. Under the influence of the concentrated solution of sulfuric acid from a bichromate receive chromic anhydride.
8. In industrial conditions pure chrome is received electrolysis of sulfate of chrome or the concentrated water solutions of its oxide. Chrome at the same time is emitted on the cathode from aluminum or stainless steel. Then metal is purified from impurity with processing by pure hydrogen at a temperature of 1500-1700 °C. In small amounts chrome can be received by chrome oxide restoration by silicon or aluminum.
9. Use of chrome is based on its resistance to corrosion and thermal stability. Its significant amount goes on decorative coverings, powder chrome is used for production of ceramic-metal products and also materials for welding electrodes.