Potassium picrate
Encyclopedia
Potassium picrate, or potassium 2,4,6-trinitrophenolate, is an organic chemical, a picrate
of potassium
. It is a reddish yellow or green crystalline material. It is a primary explosive. Anhydrous potassium picrate forms orthorhombic crystals.
Potassium picrate was first prepared as impure in mid-17th century by Johann Rudolf Glauber
by dissolving wood
in nitric acid
and neutralizing with potassium carbonate
. It is commoly made by neutralizing picric acid
by potassium carbonate. It was used since 1869. Its chief applications are in pyrotechnics
, in some whistle mix
es, as a component of explosives (with potassium nitrate
and charcoal
), propellant
s (with potassium chlorate
), and explosive primers (with lead picrate
and potassium chlorate
). Potassium picrate is not a very powerful explosive. It is somewhat shock-sensitive. In contact with flame it deflagrates
with a loud sound. If ignited in confined space, it will detonate. It is more sensitive than picric acid
.
In contact with metals (e.g. lead, calcium, iron), potassium picrate, like ammonium picrate and picric acid
, forms picrates of said metals. These are often more dangerous and more sensitive explosives. Contact with such materials therefore should be prevented.
Potassium picrate is used to determine the concentration of nonionic surfactant
s in water; materials detectable by this method are called potassium picrate active substances (PPAS).
As picric acid is barely soluble in water the reaction must be done in an appropriate solvent like methanol.
First dissolving the picric acid in methanol and then adding potassium carbonate will result in potassium picrate. Temperature control is important to prevent detonation or excessive methanol evaporation.
By comparison, the more sensitive anhydrous lead picrate detonated 10% of the time when struck by the same mass dropped from the height of 2cm.
Picrate
A picrate is a salt or an ester of picric acid . But it could also be an additional compound which picric acid forms with many aromatic hydrocarbons, aromatic amines, aliphatic amines, alkalines, and other compounds. These additional compounds are also called picrates even though they are not a...
of potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
. It is a reddish yellow or green crystalline material. It is a primary explosive. Anhydrous potassium picrate forms orthorhombic crystals.
Potassium picrate was first prepared as impure in mid-17th century by Johann Rudolf Glauber
Johann Rudolf Glauber
Johann Rudolf Glauber was a German-Dutch alchemist and chemist. Some historians of science have described him as one of the first chemical engineers...
by dissolving wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
in nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
and neutralizing with potassium carbonate
Potassium carbonate
Potassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...
. It is commoly made by neutralizing picric acid
Picric acid
Picric acid is the chemical compound formally called 2,4,6-trinitrophenol . This yellow crystalline solid is one of the most acidic phenols. Like other highly nitrated compounds such as TNT, picric acid is an explosive...
by potassium carbonate. It was used since 1869. Its chief applications are in pyrotechnics
Pyrotechnics
Pyrotechnics is the science of using materials capable of undergoing self-contained and self-sustained exothermic chemical reactions for the production of heat, light, gas, smoke and/or sound...
, in some whistle mix
Whistle mix
Whistle mix is a general term to refer to any pyrotechnic composition that emits a whistling sound when pressed into a tube and ignited. It is used as a rocket propellant, particularly in small bottle rockets...
es, as a component of explosives (with potassium nitrate
Potassium nitrate
Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...
and charcoal
Charcoal
Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...
), propellant
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
s (with potassium chlorate
Potassium chlorate
Potassium chlorate is a compound containing potassium, chlorine and oxygen atoms, with the molecular formula KClO3. In its pure form, it is a white crystalline substance. It is the most common chlorate in industrial use...
), and explosive primers (with lead picrate
Lead picrate
Lead picrate, Pb2, is an initiating explosive, and thus highly sensitive.For demonstration purposes, it can be most easily and safely prepared in situ. Picric acid is mixed with red lead , and then heated. It is not recommended that more than 50mg is ever made at any one time. At around...
and potassium chlorate
Potassium chlorate
Potassium chlorate is a compound containing potassium, chlorine and oxygen atoms, with the molecular formula KClO3. In its pure form, it is a white crystalline substance. It is the most common chlorate in industrial use...
). Potassium picrate is not a very powerful explosive. It is somewhat shock-sensitive. In contact with flame it deflagrates
Deflagration
Deflagration is a term describing subsonic combustion that usually propagates through thermal conductivity; hot burning material heats the next layer of cold material and ignites it. Most "fire" found in daily life, from flames to explosions, is deflagration...
with a loud sound. If ignited in confined space, it will detonate. It is more sensitive than picric acid
Picric acid
Picric acid is the chemical compound formally called 2,4,6-trinitrophenol . This yellow crystalline solid is one of the most acidic phenols. Like other highly nitrated compounds such as TNT, picric acid is an explosive...
.
In contact with metals (e.g. lead, calcium, iron), potassium picrate, like ammonium picrate and picric acid
Picric acid
Picric acid is the chemical compound formally called 2,4,6-trinitrophenol . This yellow crystalline solid is one of the most acidic phenols. Like other highly nitrated compounds such as TNT, picric acid is an explosive...
, forms picrates of said metals. These are often more dangerous and more sensitive explosives. Contact with such materials therefore should be prevented.
Potassium picrate is used to determine the concentration of nonionic surfactant
Surfactant
Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...
s in water; materials detectable by this method are called potassium picrate active substances (PPAS).
Synthesis
As with other picrates, potassium picrate may be produced by the neutralization of picric acid with the corresponding carbonate.As picric acid is barely soluble in water the reaction must be done in an appropriate solvent like methanol.
First dissolving the picric acid in methanol and then adding potassium carbonate will result in potassium picrate. Temperature control is important to prevent detonation or excessive methanol evaporation.
Sensitivity
According to Urbanski, Potassium picrate detonated 10% of the time when struck by a mass of 2kg dropped from the height of 21cm.By comparison, the more sensitive anhydrous lead picrate detonated 10% of the time when struck by the same mass dropped from the height of 2cm.