The substance potassium dichromate has several names, which, to a greater or lesser extent, are used depending on the scope of use of the substance itself. Traditionally, in chemical theory, the names most often used are potassium dichromate or potassium chrompeak. When it comes to industrial use, then this compound is referred to as chrompeak. In this case, it is very important to understand what kind of compound is in question, because in everyday use, chromic peak also refers to sodium dichromate with the formula Na2Cr2O7 * 2H2O. The chemical formula of potassium chrompike is K2Cr2O7.
The physical properties of potassium chromica are as follows. Externally, this substance is an orange colored crystal whose crystal lattice is variable under the influence of temperature. At its value up to 257 ° , the lattice has the form of triclinic single crystals, and when the temperature rises above 257 ° , it changes its appearance to monoclinic.
The substance potassium dichromate has a melting point of 396 ° C; when it increases above 500 ° C, the substance decomposes into K2CrO4, Cr2O3 and oxygen. The specific gravity of potassium chrompick is 2.69 g / cm3. Potassium dichromate dissolves well in aqueous solutions:
- at a temperature of 0 ° C, 4.6 grams of potassium chromic peak is completely dissolved in 100 grams of water;
- at a temperature of 25 ° C, in the same amount of water you can completely dissolve already 15.1 grams, and when the temperature rises to 50 ° C - already 37.7 grams.
In alcohols, for example, in ethanol, potassium dichromate is slightly soluble.
Potassium dichromate forms a eutectic - a composite liquid solution that crystallizes at the lowest temperature for this group of substances, the structural-compositional formula of which is H2O - K2Cr2O7 with a chromic content of 4.30% by weight. The melting point of this compound is only 0.63 ° C, and it boils at 104.8 ° C (the content of potassium chromic in solution is 52% by weight).
With the participation of a substance such as potassium dichromate, reactions proceed in acidic media if it is represented by an aqueous solution. The substance itself is also the strongest oxidizing agent, for example, during the reaction of the potassium and sulfur chromic peaks, the K2SO4 salt and chromium oxide are obtained .
When interacting with sulfuric and nitric acids, potassium dichromate forms polychromats. When heated mixtures containing this compound and hydrogen peroxide, easily explode crystals of peroxide, which, in turn, is an important component of explosives.
Industrial production of potassium chrompick is carried out through the exchange reaction of Na2Cr2O7 with KCl, in which the solution is heated to huge temperatures - about 1000 - 1300 ° C.
Potassium dichromate is used, the chemical properties of which are described above, in the manufacture of various dyes, in the textile and leather industries it is used in tanning of leathers. Widespread use in woodworking and match production, the manufacture of pyrotechnic mixtures, photography. If you dissolve potassium chrompeak in sulfuric acid, you get a very effective solution for washing glass devices in laboratories. As a component, potassium chrompeak is used in dry electrolytes, as well as in metallurgy, as an inhibitor of the process of rusting of metals and their alloys.
Chrompeak potassium is an extremely toxic compound. Drops of its solution, falling on exposed areas of the human body, destroy the skin. Even small concentrations of this substance can cause serious harm to the respiratory tract and damage the cartilage ligaments of the tissues. Cases of damage to the kidneys, liver and gastrointestinal tract are known. Therefore, when working with potassium dichromate, safety precautions should be strictly followed. Particular care should be taken to protect the respiratory system and skin.