Potassium nitrate: properties, preparation and use
You wanted to conduct your own chemical experience. A good desire, but for this you need to have a specific goal, and most importantly - the ingredients. Therefore, you sit at the computer and look for interesting recipes. Oh, it seems that they have found what they need - "Making smoke bombs". We read the list of ingredients: "Sugar, soda, that-that ... Potassium nitrate? What kind of animal is this?" - A standard train of thought in reading this recipe. Usually in this way, and learn about the existence of potassium nitrate. Naturally, there is a desire to find more information about her. Today I will try to satisfy your interest.
origin of name
First, let's talk about its name. Saltpeter is any salt that has an acidic NO3 residue taken from nitric acid, i.e. is nitrate. The chemical formula of the nitrate under discussion is KNO3, which means that the adjective “potassium” must be added to its name. But there are other options for writing it. In different sources, it can be called potassium / Indian nitrate, potassium nitrate, potassium nitrate, etc.All these names will be correct.
This saltpeter under normal conditions is colorless crystals, but when crushed it resembles a white powder. It also has an ionic structure and a hexagonal or rhombic crystal lattice. Potassium nitrate is slightly hygroscopic, tends to gently clot for some time. It is also non-volatile and odorless. It dissolves well in water, to a moderate degree - in liquid ammonia, glycerin, hydrazine, it does not dissolve in pure ether and ethanol (it can be poorly dissolved in them only if the latter are diluted with water). At its slow crystallization, needle-like and very long crystals can grow from potassium nitrate. At a temperature of 400-520 oC, its decomposition occurs, at which potassium nitrite and oxygen are formed.It is also a strong oxidizing agent that reacts with reducing agents and combustible materials, and if it is crushed in addition, the reaction takes place very actively and often accompanied by an explosion (photo). Potassium nitrate can independently ignite some organic materials, if they are in the same mixture with it.Melt potassium nitrate can be used to obtain potassium by electrolysis, but, because she has high oxidation abilities in such a state, for carrying out this experiment it is better to take potassium hydroxide.
In the Middle Ages and Novoye Vremya (that is, in the period when the powder was in frequent use), potassium nitrate was mined from the saltpets — heaps consisting of limestone materials, manure and other rotting components that had layers of brushwood or straw. They were covered with turf, holding the resulting gases. Ammonia, which was formed due to the decay of manure, accumulated in the layers, was nitrified and became first nitrogenous, and then nitric acid. The latter, when interacting with limestone, formed calcium nitrate, then it was leached with water. When wood ash was added to this mixture, the calcium carbonate in the first one was deposited. And the result was a solution of potassium nitrate. The interaction of potash and calcium nitrate is the oldest method of obtaining potassium nitrate, which is still popular.Although potash can be replaced with potassium sulfate. Potassium nitrate can be obtained in the laboratory with such reactions:
Being in nature
In nature, potassium nitrate is known as the mineral nitrocalite. The places of its largest deposits are Chile and the East Indies (this is why potassium nitrate is often called Indian). Natural potassium nitrate is azotobacteria associated with ammonia, which is released during the decomposition of nitrogenous substances. Moisture and heat contribute to this connection; therefore, the largest deposits of potassium nitrate are located in hot countries. Also in very small quantities, it is present in animals and plants.
Potassium nitrate: application
Basically it is used as a valuable fertilizer for plants (photo). It is also a very important ingredient in the composition of black powder ("smoke ducts", smoke bombs). This nitrate also benefits in optical glassmaking by bleaching and brightening technical crystal glasses and giving strength to glassware. In the food industry, this nitrate is known as the preservative E252.
Potassium nitrate (formula KNO3) can be used not only in chemistry, but also in many other industries.It can be both useful and very harmful to humans.