Bone ash

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Bone ash is a white material produced by the calcination of bones. Typical bone ash consists of about 55.82% calcium oxide, 42.39% phosphorus pentoxide, and 1.79% water.[ clarification needed ] The exact composition of these compounds varies depending upon the type of bones being used, but generally the formula for bone ash is Ca5(OH)(PO4)3. Bone ash usually has a density around 3.10 g/mL and a melting point of 1670 °C (3038 °F). Most bones retain their cellular structure through calcination.

Contents

History

Antiquity

Burnt bones have been recovered from numerous Ancient Greek sanctuaries dating from the Late Bronze Age up to the Hellenistic period. The burnt bones are often calcined with a white or blueish color, allowing archaeologists to identify them as sacrificial remains. At the sanctuary to Artemis in Eretria a round altar of fieldstones filled with soil was found, dating to the 8th century BC. The upper surface was covered with clay and animal bones were burned on top, then apparently swept off the surface with terracotta, metal objects, and pottery and trampled until the altar was eventually subsumed by the ritual debris. Some scholars have attributed these altars to chthonian rituals, but this is disputed. [1] Xenocrates of Aphrodisias reported its use as a medicinal ingredient, although cannibalism was, according to Galen, prohibited under the laws of the Roman Empire. [2]

Uses

Bone china

Bone and stone mill built in 1857. Etruria, Stoke-on-Trent Shirley's Etruscan bone and stone mill, Etruria - geograph.org.uk - 637717.jpg
Bone and stone mill built in 1857. Etruria, Stoke-on-Trent

Bone ash is a key raw material for bone china. Constituting around 50% of the body, it reacts with other raw materials in the body during firing to form, amongst other phases, anorthite.

In preparation for use in bone china, bones undergo multiple processing stages, including:

Since the 1990s, the use of synthetic alternatives to bone ash, which are based on dicalcium phosphate and tricalcium phosphate, has increased. Significant amounts of bone china is produced using these synthetic alternatives rather than bone ash. [3]

Fertilizers

Bone ash can be used alone as an organic fertilizer or it can be treated with sulfuric acid to form a "single superphosphate" fertilizer which is more water soluble:[ citation needed ]

Ca3(PO4)2 + 2 H2SO4 + 5 H2O → 2 CaSO4·2H2O + Ca(H2PO4)2·H2O

Similarly, phosphoric acid can be used to form triple superphosphate, a more concentrated phosphorus fertilizer which excludes the gypsum content found in single superphosphate: [4]

Ca3(PO4)2 + 4 H3PO4 → 3 Ca(H2PO4)2

Metal casting

Bone ash is used in foundries for various purposes. Examples include release agents and protective barriers for tools exposed to molten metal, and as a sealant for seams and cracks.[ citation needed ] Applied as a powder or water slurry,[ vague ] bone ash has many unique characteristics. First of all, the powder has high thermal stability, so it maintains its form in extremely high temperatures. The powder coating itself adheres to metal well and does not drip, run, cause much corrosion, or create noticeable streaks. Using the bone ash is easy as well, as it comes in a powder form, is easy to clean up, and does not separate into smaller parts (therefore requiring no extra mixing).[ citation needed ]

Metallurgy

Bone ash is a material often used in cupellation, a process by which precious metals (such as gold and silver) are removed from base metals.

In cupellation, base metals in an impure sample are oxidized with the help of lead and are vaporized and absorbed into a porous cupellation material, typically made of magnesium or calcium. This leaves the precious metals which do not oxidize behind. Bone ash's extremely porous and calcareous structure as well as its high melting point makes it an ideal candidate for cupellation. [5] [6]

Analysis of bone ash

The chemical analyses of three samples of ceramic grade bone ash:[ clarification needed ]

Reference [7] [8] [9]
SiO20.020.901.08
Al2O30.011.900.34
Fe2O3<0.100.300.19
TiO2<0.10-0.01
CaO55.350.552.2
MgO1.111.401.35
K2O0.401.350.12
Na2O1.332.150.51
P2O541.937.244.2
MnO<0.10--
LOI0.04.3-

In culture

Bible

From Isaiah: "And the people shall be as the burnings of lime: as thorns cut up shall they be burned in the fire"

Its use is mentioned in the Book of Amos (2:1): "I will not turn away the punishment thereof, because he burned the bones of the King of Edom into lime."

It was used in ancient formulas for white paint and cosmetic pigments, and in the cupellation process to separate silver from lead. [10] [11]

See also

Related Research Articles

<span class="mw-page-title-main">Phosphorus</span> Chemical element, symbol P and atomic number 15

Phosphorus is a chemical element; it has symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Earth. It has a concentration in the Earth's crust of about one gram per kilogram. In minerals, phosphorus generally occurs as phosphate.

<span class="mw-page-title-main">Phosphate</span> Chemical compound

In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid, a.k.a. phosphoric acid H3PO4.

<span class="mw-page-title-main">Fertilizer</span> Substance added to soils to supply plant nutrients for a better growth

A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Many sources of fertilizer exist, both natural and industrially produced. For most modern agricultural practices, fertilization focuses on three main macro nutrients: nitrogen (N), phosphorus (P), and potassium (K) with occasional addition of supplements like rock flour for micronutrients. Farmers apply these fertilizers in a variety of ways: through dry or pelletized or liquid application processes, using large agricultural equipment or hand-tool methods.

In cooking, a leavening agent or raising agent, also called a leaven or leavener, is any one of a number of substances used in doughs and batters that cause a foaming action that lightens and softens the mixture. An alternative or supplement to leavening agents is mechanical action by which air is incorporated. Leavening agents can be biological or synthetic chemical compounds. The gas produced is often carbon dioxide, or occasionally hydrogen.

<span class="mw-page-title-main">Calcium phosphate</span> Chemical compound

The term calcium phosphate refers to a family of materials and minerals containing calcium ions (Ca2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well. Calcium phosphates are white solids of nutritional value and are found in many living organisms, e.g., bone mineral and tooth enamel. In milk, it exists in a colloidal form in micelles bound to casein protein with magnesium, zinc, and citrate–collectively referred to as colloidal calcium phosphate (CCP). Various calcium phosphate minerals are used in the production of phosphoric acid and fertilizers. Overuse of certain forms of calcium phosphate can lead to nutrient-containing surface runoff and subsequent adverse effects upon receiving waters such as algal blooms and eutrophication (over-enrichment with nutrients and minerals).

<span class="mw-page-title-main">Phosphorite</span> Sedimentary rock containing large amounts of phosphate minerals

Phosphorite, phosphate rock or rock phosphate is a non-detrital sedimentary rock that contains high amounts of phosphate minerals. The phosphate content of phosphorite (or grade of phosphate rock) varies greatly, from 4% to 20% phosphorus pentoxide (P2O5). Marketed phosphate rock is enriched ("beneficiated") to at least 28%, often more than 30% P2O5. This occurs through washing, screening, de-liming, magnetic separation or flotation. By comparison, the average phosphorus content of sedimentary rocks is less than 0.2%.

<span class="mw-page-title-main">Cupellation</span> Refining process in metallurgy

Cupellation is a refining process in metallurgy in which ores or alloyed metals are treated under very high temperatures and subjected to controlled operations to separate noble metals, like gold and silver, from base metals, like lead, copper, zinc, arsenic, antimony, or bismuth, present in the ore. The process is based on the principle that precious metals typically oxidise or react chemically at much higher temperatures than base metals. When they are heated at high temperatures, the precious metals remain apart, and the others react, forming slags or other compounds.

<span class="mw-page-title-main">Calcium phosphide</span> Chemical compound

Calcium phosphide (CP) is the inorganic compound with the formula Ca3P2. It is one of several phosphides of calcium, being described as the salt-like material composed of Ca2+ and P3−. Other, more exotic calcium phosphides have the formula CaP / Ca2P2, CaP3, and Ca5P8.

<span class="mw-page-title-main">Organic fertilizer</span> Fertilizer developed from natural processes

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<span class="mw-page-title-main">Tricalcium phosphate</span> Chemical compound

Tricalcium phosphate (sometimes abbreviated TCP), more commonly known as Calcium phosphate, is a calcium salt of phosphoric acid with the chemical formula Ca3(PO4)2. It is also known as tribasic calcium phosphate and bone phosphate of lime (BPL). It is a white solid of low solubility. Most commercial samples of "tricalcium phosphate" are in fact hydroxyapatite.

<span class="mw-page-title-main">Monocalcium phosphate</span> Chemical compound

Monocalcium phosphate is an inorganic compound with the chemical formula Ca(H2PO4)2 ("AMCP" or "CMP-A" for anhydrous monocalcium phosphate). It is commonly found as the monohydrate ("MCP" or "MCP-M"), Ca(H2PO4)2·H2O. Both salts are colourless solids. They are used mainly as superphosphate fertilizers and are also popular leavening agents.

Aluminium phosphate is a chemical compound. In nature it occurs as the mineral berlinite. Many synthetic forms of aluminium phosphate are known. They have framework structures similar to zeolites and some are used as catalysts, ion-exchangers or molecular sieves. Commercial aluminium phosphate gel is available.

In metallurgy, refining consists of purifying an impure metal. It is to be distinguished from other processes such as smelting and calcining in that those two involve a chemical change to the raw material, whereas in refining, the final material is usually identical chemically to the original one, only it is purer. The processes used are of many types, including pyrometallurgical and hydrometallurgical techniques.

<span class="mw-page-title-main">Trimagnesium phosphate</span> Chemical compound

Trimagnesium phosphate describes inorganic compounds with formula Mg3(PO4)2.xH2O. They are magnesium acid salts of phosphoric acid, with varying amounts of water of crystallization: x = 0, 5, 8, 22.

<span class="mw-page-title-main">Taranakite</span> Iron-aluminium phosphate mineral

Taranakite is a hydrated alkali iron-aluminium phosphate mineral with chemical formula (K,Na)3(Al,Fe3+)5(PO4)2(HPO4)6·18 H2O. It forms from the reaction of clay minerals or aluminous rocks with solutions enriched in phosphate derived from bat or bird guano or, less commonly, from bones or other organic matter. Taranakite is most commonly found in humid, bat inhabited caves near the boundary of guano layers with the cave surface. It is also found in perennially wet coastal locations that have been occupied by bird colonies. The type location, and its namesake, the Sugar Loaf Islands off Taranaki, New Zealand, is an example of a coastal occurrence.

<span class="mw-page-title-main">Bioceramic</span> Type of ceramic materials that are biocompatible

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Zirconium phosphates (zirconium hydrogen phosphate) are acidic, inorganic cation exchange materials that have a layered structure with formula Zr(HPO4)2∙nH2O. These salts have high thermal and chemical stability, solid state ion conductivity, resistance to ionizing radiation, and the capacity to incorporate different types of molecules with different sizes between their layers. There are various phases of zirconium phosphate which vary in their interlaminar spaces and their crystalline structure. Among all the Zirconium phosphate phases the most widely used are the alpha (Zr(HPO4)2∙H2O) and the gamma (Zr(PO4)(H2PO4)∙2H2O) phase. The salts have been widely used in several applications such as: drug delivery, catalysis, nanocomposite, nuclear waste management, clinical dialyzer, among others.

Tetracalcium phosphate is the compound Ca4(PO4)2O, (4CaO·P2O5). It is the most basic of the calcium phosphates, and has a Ca/P ratio of 2, making it the most phosphorus poor phosphate. It is found as the mineral hilgenstockite, which is formed in industrial phosphate rich slag (called "Thomas slag"). This slag was used as a fertiliser due to the higher solubility of tetracalcium phosphate relative to apatite minerals. Tetracalcium phosphate is a component in some calcium phosphate cements that have medical applications.

References

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  3. Mussi, Susan. "Bone ash". Ceramic Dictionary. Retrieved 22 July 2015.
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