from the weak carbonic acid (it is little resistant and can only exist in the dilute solution) by reacting with alkalis and acidic medium obtained salts are otherwise called bicarbonates and carbonates, respectively.Reaction equations can be written: H2CO3 + KOH → KHCO3 + H2O and H2CO3 + 2KOH → K2CO3 + 2H2O.The first obtained sodium, potassium, and the second - of potassium carbonate.Formula acid salt - KHCO3, and the average - K2CO3.The molar mass of potassium carbonate is equal to 138.2 g / mol.In appearance resembles salt white crystalline powder, which is not combustible, melts at 891 C, without reaching the boiling point, the salt decomposes.Potassium carbonate hygroscopic, readily soluble in water: 100 ml at 20 ° C - 110.5 g, and at 100 C - 156 g of salt.But in alcohol or acetone the substance does not dissolve.
In the old days was called potash, potassium carbonate, the word comes from the Latin name «potassa».Potash is one of the oldest salt, which have been known to people long ago.In Europe, up to the last century, potash was one of the most important chemicals that have commercial value.In Russia, for the production of potash by Peter the Great in 1721, it was established a monopoly.Currently, the Russian Federation, as well as in Armenia, Kazakhstan, Belarus, Ukraine, Turkmenistan, Moldova, Uzbekistan is a chemical spread interstate standard GOST 10690-73.Potash is, according to GOST 12.1.005-88, the substances of the third class of danger, in contact with mucous membranes or moist skin causes irritation.
When mixed with water, potassium carbonate, then it is dissolved in a lot of heat, i.e. K2CO3 hydrolysis reaction is exothermic and under the influence of water is the formation of new substances.The salt of the dibasic carbonic acid hydrolyzed stepwise.First formed acid salt: H2O + K2CO3 → KHCO3 + KOH.Then loosely flowing second stage expansion is already acidic salt water: H2O + KHCO3 → H2CO3 + KOH.Since the hydrolysis of potassium carbonate as well as other salts of weak acids proceeds with the formation of hydroxyl ions OH-, the pH of their aqueous solutions is always greater than 7, and the medium is alkaline.
potash in the 17th century in Russia was obtained by leaching wood ashes.The wooden troughs prepared alkaline solution by spraying hot water ash.This solution is then poured into a brick fireplace with burning firewood.Potassium carbonate crystallized very dense layer on the bottom of the hearth, with a crowbar potash mined and laid the barrels, clogging them tightly.It required a certain skill, to the solution was evaporated, and the fire did not proffer.So the craft "polivachey" began to teach in their teens, and only a few years acquired certain working skills and become a master of his craft.For example: The burning fire is always formed white ash, the main part of it - it's potash.Today, I realized another industrial process - obtained through the electrolysis of potassium hydroxide pass carbon dioxide: 2KOH + CO2 → K2CO3 + H2O.The result potash and water.
Potassium carbonate is used in the production of soap and glass.In the laboratory, it is used as a mild desiccant in cases when other agents such as calcium chloride or magnesium sulfate, is not permitted.It is not suitable for drying the acidic compounds, but may be used for the drying of organic products containing small amounts of acid impurities.Potassium carbonate is used to extinguish fires, Class B, because it refers to chemical powders, and able to inhibit and extinguish the burning process.It has a higher extinguishing efficiency than salts such as sodium carbonate, sodium sulfate, sodium fluoride or sodium hydrogen carbonate.Its inhibitory efficiency of combustion processes is also higher than that of sodium carbonate, sodium sulfate, aluminum oxide and calcium carbonate.In the glass industry K2CO3 used in the manufacture of laboratory (refractory), optical or potash glass, and glass for glassware manufacture.In addition, potash demand in the chemical, agricultural, medical and food industries.
