Calcium dihydrogen phosphate
Encyclopedia
Monocalcium phosphate is a chemical compound with the formula Ca(H2PO4)2. It is commonly found as the monohydrate, Ca(H2PO4)2·H2O.
is an essential nutrient
and therefore is a common component of agricultural fertilizer
s. Tricalcium phosphate
Ca3(PO4)2, a major component of phosphate rock such as phosphorite
, apatite
, and other phosphate minerals
, is too insoluble to be an efficient fertilizer. Therefore it can be converted into the more soluble monocalcium phosphate, generally by the use of sulfuric acid
H2SO4. The result is hydrated to turn the calcium sulfate into the dihydrate
gypsum
and sold as superphosphate of lime. Alternately phosphate rock may be treated with phosphoric acid to produce a purer form of monocalcium phosphate and is sold as triple phosphate.
produced by the action of concentrated sulfuric acid
on powdered phosphate rock.
"In 1840, Justus Von Liebig
wrote, 'The crops on the field diminish or increase in exact proportion to the diminution or increase of the mineral substances conveyed to it in manure.' Von Liebig was the first to discover that phosphate of lime in bone meal
could be rendered more readily available to plants by treatment with sulfuric acid
. Sir John Bennett Lawes about the same time discovered that phosphate rock underwent the same reaction and could be used as a source ingredient. In the 1840s, scientists found that coprolite
s could be dissolved in sulfuric acid to produce what became known as superphosphate. Bennett Lawes was the first to manufacture superphosphate at his factory in Deptford, England in 1842."
An expanded market for superphosphate emerged in the second half of the 20th century by the development of aerial topdressing in New Zealand
which allowed superphosphate to be spread economically over large areas.
Superphosphate can be formed naturally in large quantities by the buildup of guano
, or bird feces, resulting in deposits around sea bird colonies which can be mined. The most famous mining site is the island of Nauru
in the South Pacific from which much of the "soil" was mined, producing temporary wealth for the inhabitants.
produced by the action of concentrated phosphoric acid
on ground phosphate rock.
Ca3(PO4)2(s) + 4 H3PO4(aq) → 3 Ca 2+(aq) + 6 H2PO41-(aq) → 3 Ca(H2PO4)2(aq)
The active ingredient of the product, monocalcium phosphate, is identical to that of superphosphate, but without the presence of calcium sulfate
that is formed if sulfuric acid
is used instead of phosphoric acid
. The phosphorus content of triple superphosphate (17 - 23% P; 44 to 52% P2O5) is therefore greater than that of superphosphate (7 - 9.5% P; 16 to 22% P2O5). Triple superphosphate was the most common phosphate (P) fertilizer in the USA until the 1960s, when ammonium phosphate
s became more popular. It is produced in granular and nongranular form and is used both in fertilizer blends (with potassium
and nitrogen
fertilizers) and by itself.
to cause baked goods to rise. Because it is acidic, when combined with an alkali ingredient, commonly sodium bicarbonate
(baking soda) or potassium bicarbonate
, it reacts to produce carbon dioxide
and a salt. Outward pressure of the carbon dioxide gas causes the rising effect. When combined in a ready-made baking powder
, the acid and alkali ingredients are included in the right proportions such that they will exactly neutralize each other and not significantly affect the overall pH
of the product.
Fertilizer
PhosphorusPhosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
is an essential nutrient
Essential nutrient
An essential nutrient is a nutrient required for normal body functioning that either cannot be synthesized by the body at all, or cannot be synthesized in amounts adequate for good health , and thus must be obtained from a dietary source...
and therefore is a common component of agricultural fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
s. Tricalcium phosphate
Tricalcium phosphate
Tricalcium phosphate is a calcium salt of phosphoric acid with the chemical formula Ca32. It is also known as tribasic calcium phosphate or "bone ash" ....
Ca3(PO4)2, a major component of phosphate rock such as phosphorite
Phosphorite
Phosphorite, phosphate rock or rock phosphate is a non-detrital sedimentary rock which contains high amounts of phosphate bearing minerals. The phosphate content of phosphorite is at least 15 to 20% which is a large enrichment over the typical sedimentary rock content of less than 0.2%...
, apatite
Apatite
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH−, F−, Cl− or Br− ions, respectively, in the crystal...
, and other phosphate minerals
Phosphate minerals
Phosphate minerals are those minerals that contain the tetrahedrally coordinated phosphate anion along with the freely substituting arsenate and vanadate...
, is too insoluble to be an efficient fertilizer. Therefore it can be converted into the more soluble monocalcium phosphate, generally by the use of sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
H2SO4. The result is hydrated to turn the calcium sulfate into the dihydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
gypsum
Gypsum
Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...
and sold as superphosphate of lime. Alternately phosphate rock may be treated with phosphoric acid to produce a purer form of monocalcium phosphate and is sold as triple phosphate.
Superphosphate
Superphosphate is a fertilizerFertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
produced by the action of concentrated sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
on powdered phosphate rock.
- Ca3(PO4)2(s) + 2 H2SO4(aq) → 2 CaSO4(aq) + Ca(H2PO4)2(aq)
"In 1840, Justus Von Liebig
Justus von Liebig
Justus von Liebig was a German chemist who made major contributions to agricultural and biological chemistry, and worked on the organization of organic chemistry. As a professor, he devised the modern laboratory-oriented teaching method, and for such innovations, he is regarded as one of the...
wrote, 'The crops on the field diminish or increase in exact proportion to the diminution or increase of the mineral substances conveyed to it in manure.' Von Liebig was the first to discover that phosphate of lime in bone meal
Bone meal
Bone meal is a mixture of crushed and coarsely ground bones that is used as an organic fertilizer for plants and formerly in animal feed. As a slow-release fertilizer, bone meal is primarily used as a source of phosphorus....
could be rendered more readily available to plants by treatment with sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
. Sir John Bennett Lawes about the same time discovered that phosphate rock underwent the same reaction and could be used as a source ingredient. In the 1840s, scientists found that coprolite
Coprolite
A coprolite is fossilized animal dung. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour rather than morphology. The name is derived from the Greek words κοπρος / kopros meaning 'dung' and λιθος / lithos meaning 'stone'. They...
s could be dissolved in sulfuric acid to produce what became known as superphosphate. Bennett Lawes was the first to manufacture superphosphate at his factory in Deptford, England in 1842."
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
which allowed superphosphate to be spread economically over large areas.
Superphosphate can be formed naturally in large quantities by the buildup of guano
Guano
Guano is the excrement of seabirds, cave dwelling bats, and seals. Guano manure is an effective fertilizer due to its high levels of phosphorus and nitrogen and also its lack of odor. It was an important source of nitrates for gunpowder...
, or bird feces, resulting in deposits around sea bird colonies which can be mined. The most famous mining site is the island of Nauru
Nauru
Nauru , officially the Republic of Nauru and formerly known as Pleasant Island, is an island country in Micronesia in the South Pacific. Its nearest neighbour is Banaba Island in Kiribati, to the east. Nauru is the world's smallest republic, covering just...
in the South Pacific from which much of the "soil" was mined, producing temporary wealth for the inhabitants.
Triple superphosphate
Triple superphosphate is a fertilizerFertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
produced by the action of concentrated phosphoric acid
Phosphoric acid
Phosphoric acid, also known as orthophosphoric acid or phosphoric acid, is a mineral acid having the chemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more general way...
on ground phosphate rock.
Ca3(PO4)2(s) + 4 H3PO4(aq) → 3 Ca 2+(aq) + 6 H2PO41-(aq) → 3 Ca(H2PO4)2(aq)
The active ingredient of the product, monocalcium phosphate, is identical to that of superphosphate, but without the presence of calcium sulfate
Calcium sulfate
Calcium sulfate is a common laboratory and industrial chemical. In the form of γ-anhydrite , it is used as a desiccant. It is also used as a coagulant in products like tofu. In the natural state, unrefined calcium sulfate is a translucent, crystalline white rock...
that is formed if sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
is used instead of phosphoric acid
Phosphoric acid
Phosphoric acid, also known as orthophosphoric acid or phosphoric acid, is a mineral acid having the chemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more general way...
. The phosphorus content of triple superphosphate (17 - 23% P; 44 to 52% P2O5) is therefore greater than that of superphosphate (7 - 9.5% P; 16 to 22% P2O5). Triple superphosphate was the most common phosphate (P) fertilizer in the USA until the 1960s, when ammonium phosphate
Ammonium phosphate
Ammonium phosphate is the salt of ammonia and phosphoric acid. It has the formula 3PO4 and consists of ammonium cations and phosphate anion. It is obtained as a crystalline powder upon mixing concentrated solutions of ammonia and phosphoric acid, or on the addition of excess of ammonia to the...
s became more popular. It is produced in granular and nongranular form and is used both in fertilizer blends (with 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...
and nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
fertilizers) and by itself.
Leavening agent
Calcium dihydrogen phosphate is also used in the food industry as a leavening agentLeavening agent
A leavening agent is any one of a number of substances used in doughs and batters that cause a foaming action which lightens and softens the finished product...
to cause baked goods to rise. Because it is acidic, when combined with an alkali ingredient, commonly sodium bicarbonate
Sodium bicarbonate
Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . The natural mineral form is...
(baking soda) or potassium bicarbonate
Potassium bicarbonate
Potassium bicarbonate , is a colorless, odorless, slightly basic, salty substance...
, it reacts to produce carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
and a salt. Outward pressure of the carbon dioxide gas causes the rising effect. When combined in a ready-made baking powder
Baking powder
Baking powder is a dry chemical leavening agent used to increase the volume and lighten the texture of baked goods such as muffins, cakes, scones and American-style biscuits. Baking powder works by releasing carbon dioxide gas into a batter or dough through an acid-base reaction, causing bubbles in...
, the acid and alkali ingredients are included in the right proportions such that they will exactly neutralize each other and not significantly affect the overall pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
of the product.