Making Potassium Nitrate [Published]
AndersHoveland
Acolyte
Potassium Nitrate (KNO3) is not itself an explosive, but it is the main ingredient in black powder, and is also a precursor for the preparation of nitric acid.
KNO3 can actually be made. In old times, on the Continent, they would make a compost pile and frequently urinate on it. Then the dirt would be mixed with some hot water and the resulting muddy water filtered through a cloth. Potash (potassium salt) would be added and the mixture boiled down to a smaller volume. Making the resulting mix cold would cause saltpetre (KNO3) to crystallize out. Potash is basically just regular wood ash, but it is sometimes boiled with CaCl2 to precipitate out all the oxalic acid in the ash, since CaC2O4 is not soluble.
Over a plastic sheet is placed a mixture of dirt, ashes from fire, and dead plant material. Small twig branches, straw and leaves are added, to make the heap porous. A light covering is placed over it. The heap is frequently periodically watered with urine or animal excrement, and turned over every week. After about eight months, salt petre (KNO3) will have formed in sufficient quantities.
LEACHING.
When the process of nitrification is complete, the earth of the heaps must be leached. In the process of leaching, in order to save fuel, we must strive to get as strong a solution as possible, and at the same time to extract all or nearly all the nitre. These two objects can only be attained by repeated leachings of the same earth, the ley thus obtained being used on fresh earth until the strength of the ley is sufficient. A quantity of nitrified earth is thrown into a vat, or ash-tub, or barrel, or hogshead with an aperture below, closely stopped and covered lightly with straw. Water is added, about half as much in volume as the earth. After stirring, this is allowed to remain twelve hours. After opening, about half the water runs through containing one-half the nitre. Pure water, in quantity half as much as first used, is again poured on, and after a few moments run through. This will contain one half the remaining nitre, and therefore one fourth of the original quantity. The successive leachings become progessively less yielding, until, after the sixth leaching, the earth is considered as sufficiently exhausted. The exhausted earth is thrown back on the nitre-beds, or else mixed with black earth to form new beds. The leys thus obtained are used upon fresh earth until the solution is of sufficient density to bear an egg. It then contains about a pound of salt to a gallon of liquid.
CONVERSION.
The ley thus obtained contains, besides nitrate of potash (nitre), also nitrate of lime and magnesia, and chlorides of sodium and potassium. The object of the next process is to convert all other nitrates into nitrate of potash. This is done by adding wood ashes. The potash of the ashes takes all the nitric acid of the other nitrates forming the nitrate of potash (nitre), and the lime and magnesia are precipitated as an insoluble sediment. Sometimes the ashes is mixed with the nitrified earth and leached together, sometimes the saltpetre ley is filtered through wood ashes, sometimes the ley of ashes is added to the saltpetre ley. In either case the result is the same.
CRYSTALLIZATION.
The crude product thus obtained is then poured off from the precipitate, into a metal boiler. It still contains common salt (chloride of sodium) in considerable ammounts, and some other impurities in smaller quantities. It is a peculiarity of nitre, that it is much more soluble than common salt in boiling water, but much less soluble in cold water. As the boiling proceeds, therefore, and the solution becomes more concentrated, the common salt is, most of it, precipitated in small crystals, as a sandy sediment, and may be raked out. Much organic matter rises as scum, and must also be removed. When the concentration has reached almost the point of saturation, the boiler must be allowed to cool. This is known by letting fall a drop of the boiling liquid upon a cold metallic surface; if it quickly crystallizes, it is time to stop the boiling. It is now poured into large receivers and left to cool. As the ley cools, nearly the whole of the nitre separates in the form of crystals, which sink to the bottom. These are then removed, drained by throwing them in baskets, and dried by gentle beat. The mother-liquor is either thrown back into the boilers, or else used in watering the heaps. The product thus obtained is the crude saltpetre of commerce. It still contains fifteen to twenty-five per cent. of impurities, principally common salt (chloride of sodium), chloride of potassium and organic matter. In this impure form it is usually brought to market.
There is another process, refining, by which the whole of the impurities is removed.
REFINING.
One hundred gallons of water is poured into a boiler, and crude saltpetre added from time to time, while the liquid is heating, until four thousand pounds are introduced. This will make a saturated solution of nitre. The scum must be removed, and the undissolved common salt scraped out. About sixty gallons cold water is now added gradually, so as not to cool the liquid too suddenly. From one to one and a-half pounds of glue, dissolved in hot water, is added, with stirring. Blood is sometimes used instead of glue. The glue seizes upon the organic matter, and they rise together as scum, which is removed. Continue the boiling until the liquid is clear. The liquid is then suffered to cool to one hundred and ninety-four degrees, and then carefully ladled out into the crystallizers. These are large shallow vats, with the bottom sloping gently to the middle. In these the cooling is completed, with constant stirring. In the process of cooling nearly the whole of the nitre is deposited in very fine, needle-like crystals, which, as they deposit, are removed and drained. In this condition it is called saltpetre flour. The object of the constant stirring is to prevent the aggregation of the crystals into masses, from which it is difficult to remove the adhering mother-liquor. The saltpetre flour is then washed of all adhering mother-liquor. A saturated solution of pure nitre is added, in quantity sufficient to moisten thoroughly the whole mass. After remaining two or three hours to drain, the solution is removed. The saturated solution of nitre cannot, of course, dissolve any more nitre, but dissolves freely the impurities present in the adhering mother-liquor. Last of all, a small quantity of pure water, only about one pound to fifty-three pounds of the nitre to be washed, is added in the same manner, and removed at the end of two hours. The nitre is now dried by gentle heat and constant stirring, and may be considered quite pure, and fit for the manufacture of gunpowder.
or see http://fryingcolors.com/saltpeter.html
HOW IT WORKS
Bacteria in decaying compost break down nitrogen-containing organic compounds and oxidize them with air to form nitrates. Adding ammonium sulfate fertilizer or urine (which contains urea) adds more usable nitrogen, which leads to formation of more nitrates. Some bacteria can even turn nitrogen gas from the air into ammonia or nitrates. Scientists have long sought a process which can replicate what these bacteria are capable of doing, without requiring extreme heat in a pressurized container. Recently such a process was found, but it is very impractical.
KNO3 can actually be made. In old times, on the Continent, they would make a compost pile and frequently urinate on it. Then the dirt would be mixed with some hot water and the resulting muddy water filtered through a cloth. Potash (potassium salt) would be added and the mixture boiled down to a smaller volume. Making the resulting mix cold would cause saltpetre (KNO3) to crystallize out. Potash is basically just regular wood ash, but it is sometimes boiled with CaCl2 to precipitate out all the oxalic acid in the ash, since CaC2O4 is not soluble.
Over a plastic sheet is placed a mixture of dirt, ashes from fire, and dead plant material. Small twig branches, straw and leaves are added, to make the heap porous. A light covering is placed over it. The heap is frequently periodically watered with urine or animal excrement, and turned over every week. After about eight months, salt petre (KNO3) will have formed in sufficient quantities.
LEACHING.
When the process of nitrification is complete, the earth of the heaps must be leached. In the process of leaching, in order to save fuel, we must strive to get as strong a solution as possible, and at the same time to extract all or nearly all the nitre. These two objects can only be attained by repeated leachings of the same earth, the ley thus obtained being used on fresh earth until the strength of the ley is sufficient. A quantity of nitrified earth is thrown into a vat, or ash-tub, or barrel, or hogshead with an aperture below, closely stopped and covered lightly with straw. Water is added, about half as much in volume as the earth. After stirring, this is allowed to remain twelve hours. After opening, about half the water runs through containing one-half the nitre. Pure water, in quantity half as much as first used, is again poured on, and after a few moments run through. This will contain one half the remaining nitre, and therefore one fourth of the original quantity. The successive leachings become progessively less yielding, until, after the sixth leaching, the earth is considered as sufficiently exhausted. The exhausted earth is thrown back on the nitre-beds, or else mixed with black earth to form new beds. The leys thus obtained are used upon fresh earth until the solution is of sufficient density to bear an egg. It then contains about a pound of salt to a gallon of liquid.
CONVERSION.
The ley thus obtained contains, besides nitrate of potash (nitre), also nitrate of lime and magnesia, and chlorides of sodium and potassium. The object of the next process is to convert all other nitrates into nitrate of potash. This is done by adding wood ashes. The potash of the ashes takes all the nitric acid of the other nitrates forming the nitrate of potash (nitre), and the lime and magnesia are precipitated as an insoluble sediment. Sometimes the ashes is mixed with the nitrified earth and leached together, sometimes the saltpetre ley is filtered through wood ashes, sometimes the ley of ashes is added to the saltpetre ley. In either case the result is the same.
CRYSTALLIZATION.
The crude product thus obtained is then poured off from the precipitate, into a metal boiler. It still contains common salt (chloride of sodium) in considerable ammounts, and some other impurities in smaller quantities. It is a peculiarity of nitre, that it is much more soluble than common salt in boiling water, but much less soluble in cold water. As the boiling proceeds, therefore, and the solution becomes more concentrated, the common salt is, most of it, precipitated in small crystals, as a sandy sediment, and may be raked out. Much organic matter rises as scum, and must also be removed. When the concentration has reached almost the point of saturation, the boiler must be allowed to cool. This is known by letting fall a drop of the boiling liquid upon a cold metallic surface; if it quickly crystallizes, it is time to stop the boiling. It is now poured into large receivers and left to cool. As the ley cools, nearly the whole of the nitre separates in the form of crystals, which sink to the bottom. These are then removed, drained by throwing them in baskets, and dried by gentle beat. The mother-liquor is either thrown back into the boilers, or else used in watering the heaps. The product thus obtained is the crude saltpetre of commerce. It still contains fifteen to twenty-five per cent. of impurities, principally common salt (chloride of sodium), chloride of potassium and organic matter. In this impure form it is usually brought to market.
There is another process, refining, by which the whole of the impurities is removed.
REFINING.
One hundred gallons of water is poured into a boiler, and crude saltpetre added from time to time, while the liquid is heating, until four thousand pounds are introduced. This will make a saturated solution of nitre. The scum must be removed, and the undissolved common salt scraped out. About sixty gallons cold water is now added gradually, so as not to cool the liquid too suddenly. From one to one and a-half pounds of glue, dissolved in hot water, is added, with stirring. Blood is sometimes used instead of glue. The glue seizes upon the organic matter, and they rise together as scum, which is removed. Continue the boiling until the liquid is clear. The liquid is then suffered to cool to one hundred and ninety-four degrees, and then carefully ladled out into the crystallizers. These are large shallow vats, with the bottom sloping gently to the middle. In these the cooling is completed, with constant stirring. In the process of cooling nearly the whole of the nitre is deposited in very fine, needle-like crystals, which, as they deposit, are removed and drained. In this condition it is called saltpetre flour. The object of the constant stirring is to prevent the aggregation of the crystals into masses, from which it is difficult to remove the adhering mother-liquor. The saltpetre flour is then washed of all adhering mother-liquor. A saturated solution of pure nitre is added, in quantity sufficient to moisten thoroughly the whole mass. After remaining two or three hours to drain, the solution is removed. The saturated solution of nitre cannot, of course, dissolve any more nitre, but dissolves freely the impurities present in the adhering mother-liquor. Last of all, a small quantity of pure water, only about one pound to fifty-three pounds of the nitre to be washed, is added in the same manner, and removed at the end of two hours. The nitre is now dried by gentle heat and constant stirring, and may be considered quite pure, and fit for the manufacture of gunpowder.
or see http://fryingcolors.com/saltpeter.html
HOW IT WORKS
Bacteria in decaying compost break down nitrogen-containing organic compounds and oxidize them with air to form nitrates. Adding ammonium sulfate fertilizer or urine (which contains urea) adds more usable nitrogen, which leads to formation of more nitrates. Some bacteria can even turn nitrogen gas from the air into ammonia or nitrates. Scientists have long sought a process which can replicate what these bacteria are capable of doing, without requiring extreme heat in a pressurized container. Recently such a process was found, but it is very impractical.
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