Calcium carbonate phosphate compounds

Additionally, the calcium carbonate phosphate mineral dahUite (Caio(P04)6(C03).H20) has been identified in ivory (LeGeros et al., 1960 McDoimell, 1965). Several of the phosphates are also known to occur in urinary calculi and may therefore be present in gallstones. A fuller discussion of calciinn phosphates and alhed compounds as found in bone, ivory and gallstones can be found in the relevant entries. 

Calcium. Calcium is the fifth most abundant element in the earth s cmst. There is no foreseeable lack of this resource as it is virtually unlimited. Primary sources of calcium are lime materials and gypsum, generally classified as soil amendments (see Calcium compounds). Among the more important calcium amendments are blast furnace slag, calcitic limestone, gypsum, hydrated lime, and precipitated lime. Fertilizers that carry calcium are calcium cyanamide, calcium nitrate, phosphate rock, and superphosphates. In addition, there are several organic carriers of calcium. Calcium is widely distributed in nature as calcium carbonate, chalk, marble, gypsum, fluorspar, phosphate rock, and other rocks and minerals. 

Although they may be completely soluble in the lower temperature bulk water, these compounds (eg, calcium carbonate, calcium phosphate, and magnesium siUcate) supersaturate in the higher temperature water adjacent to the heat-transfer surface and precipitate on the surface. 

Bone is a porous tissue composite material containing a fluid phase, a calcified bone mineral, hydroxyapatite (HA), and organic components (mainly, collagen type). The variety of cellular and noncellular components consist of approximately 69% organic and 22% inorganic material and 9% water. The principal constiments of bone tissue are calcium (Ca ), phosphate (PO ), and hydroxyl (OH ) ions and calcium carbonate. There are smaller quantities of sodium, magnesium, and fluoride. The major compound, HA, has the formula Caio(P04)g(OH)2 in its unit cell. The porosity of bone includes membrane-lined capillary blood vessels, which function to transport nutrients and ions in bone, canaliculi, and the lacunae occupied in vivo by bone cells (osteoblasts), and the micropores present in the matrix. 

Silver white, relatively soft metal that is only applied in alloys. Oxygen and water attack pure Ca. The most prominent compound is the oxide (CaO) = burnt calcium, which hardens to calcium carbonate in mortar. Annual production of about 120 million tons. Burnt gypsum (CaS04 0.5 H20) hardens with water. A great step in evolution was the replacement of hard shells of brittle calcium carbonate by an internal skeleton of tough calcium phosphate (hydroxylapatite)-protein composite. Calcium is essential for all life forms. The daily requirement is 0.7-1.0 g. Humans (70 kg) contain 1 kg of calcium. Calcium silicate is the main component of cement. Marble is calcium carbonate in polycrystalline form and the favorite material of sculptors. 

Write formulas for each of the following compounds (a) calcium hydrogen carbonate, (b) disodium hydrogen phosphate, (c) sodium dihydrogen phosphate, and (d) calcium dihydrogen phosphate. 

Some of the important compounds containing the group IA and IIA metals are the carbonates, nitrates, sulfates, and phosphates. We have already mentioned the mineral trona as the source of sodium carbonate. Calcium carbonate is found in many forms that include chalk, calcite, aragonite, and marble, as well as in egg shells, coral, and seashells. In addition to its use as a building material, calcium phosphate is converted into fertilizers in enormous quantities (see Chapter 14). 

Phosphate and phosphonate molecules have a very high affinity for calcium carbonate surfaces, as shown by their influence on the precipitation and growth of calcite [164-166]. Accordingly, organophosphorus compounds such as alkylphosphoric acids [167-169] and phosphonic acid-terminated polyoxyethylene [170, 171] have been used to modify the surface of CaCOs powders. 

The ammonium salt produced or consumed in largest amounts is ammonium nitrate. It is used widely as a fertilizer, and is the leading nitrogen fertilizer in the world. An advantage of this compound over other ammonium fer-tihzers is that it provides both nitrate and ammonia to soil without changing the pH. Also, it is used as a mixed fertihzer with other compounds, such as calcium phosphate, or calcium carbonate. It also is used as an explosive for... 

A biodegradation accelerant increases or accelerates the rate of biodegradation in the environment. For example, calcium carbonate, calcium hydroxide, calcium oxide, barium oxide, barium hydroxide, sodium silicate, calcium phosphate, magnesium oxide, may accelerate the biodegradation process. These compounds may also act as processing aids. A commonly used compound is calcium carbonate (20). 

Various calcium sails and organic compounds lull into this category of dietary supplements and are frequently used in feeds and foods. Some of the more Important additives include calcium carbonate, calcium glycerophosphate, calcium phosphate (di- and monobasic), calcium pyrophosphate, calcium sulfate, and calcium pantothenate. 

The development of the types of skeletons that characterize Tommotian faunas constituted a major evolutionary event. Although skeletons are known to support soft tissue and to facilitate locomotion, such adaptive functions cannot explain why so many different kinds of skeletons developed suddenly in the early part of Tommotian time. It has been suggested that a chemical change within the oceans triggered the production of these skeletons, but this hypothesis does not explain why some skeletons were composed of calcium carbonate and others of calcium phosphate, two compounds with quite different chemical properties. The rapid evolution of various kinds of external skeletons is probably in part attributable to the fact that animals... 

Besides calcium carbonate, there are three other calcium-based compounds that will scale RO membranes. These compounds are calcium sulfate, phosphate, and fluoride. Although there are no specified feed water guidelines for these compounds, they are worth investigating. 

Calcium phosphate has become a common problem with the increase in treatment of municipal waste-water for reuse. Surface waters can also contain phosphate. Calcium phosphate compounds can contain hydroxyl, chloride, fluoride, aluminum, and/ or iron. Several calcium phosphate compounds have low solubility, as shown in Table 7.2. Solubility for calcium carbonate and barium sulfate are also shown by comparison. The potential for scaling RO membranes with the calcium phosphate compounds listed in Table 7.2 is high and will occur when the ion product exceeds the solubility constant. This can occur at orthophosphate concentrations as low as 0.5 ppm. Sodium softening or antisealants together with low pH help to control phosphate-based scaling. 

The lithosphere consists primarily of rocks and minerals. Some of the important classes of metal compounds found in the lithosphere are oxides, sulfides, silicates, phosphates, and carbonates. The atmosphere surrounding the earth contains oxygen, so several metals such as iron, aluminum, tin, magnesium, and chromium are found in nature as the oxides. Sulfur is found in many places in the earth s crust (particularly in regions where there is volcanic activity), so some metals are found combined with sulfur as metal sulfides. Metals found as sulfides include copper, silver, nickel, mercury, zinc, and lead. A few metals, especially sodium, potassium, and magnesium, are found as the chlorides. Several carbonates and phosphates occur in the lithosphere, and calcium carbonate and calcium phosphate are particularly important minerals. 

Some of the Group IA and IIA metals are found in nature in the form of carbonates, silicates, nitrates, and phosphates. For example, calcium carbonate is one of the most important naturally occurring compounds, and it is found in several forms. The most common form of calcium carbonate is limestone, which is used extensively as a building stone as well as the source of lime. Other forms include chalk, calcite, aragonite, Iceland spar, marble, and onyx. Many other materials such as egg shells, coral, pearls, and seashells are composed predominantly of calcium carbonate. Thus, it is one of the most widely occurring compounds in nature. 

Sources of Phosphates.—The most available and most exploited sources of phosphorus and its compounds at the present day are the phosphatic rocks, or phosphorites, which consist of tribasic calcium phosphate associated with calcium carbonate, alumina, magnesia, etc.1 Phosphates of alumina are also useful. The production of these secondary rocks from the older rocks has already been mentioned (p. 208). Although the apatites themselves, as pure minerals, contain a high proportion of phosphoric anhydride, they are difficult to decompose, and are admixed with other minerals of a still more refractory nature. 

Typically, bone has a solid outer portion called cortical bone and a porous inner part called cancellous bone. The amounts of each vary with location in the body. The cortical bone is a ceramic containing calcium compounds and viscous liquids, a protein called collagen , and an organic polymer. In addition to HAP, bone consists of calcium carbonate and calcium phosphate. HAP is 69 wt.% of total calcium phosphate compounds [4]. Part of the Ca in these compounds is substituted by Na, K, Mg, and Sr. Hydroxyl ions in the HAP are also substituted by F, CO3, or Cl, which makes the apatite a fluoroapatite, dahllite or chloroapatite, respectively. These substitutions are considered to play significant roles in the structure and mechanical properties of bones. 

The use of the pure molybdate-based pigments available on the market is limited due to their cost [5.53, 5.56]. To overcome this disadvantage, molybdate, and phosphate pigments are combined (see Section 5.2.5.2.) or molybdate compounds are apphed to inorganic fillers like calcium carbonate and/or zinc oxide [5.56, 5.91]. 

Oxygen occurs in all kinds of minerals. Some common examples include the oxides, carbonates, nitrates, sulfates, and phosphates. Oxides are chemical compounds that contain oxygen and one other element. Calcium oxide, or lime or quicklime (CaO), is an example. Carbonates are compounds that contain oxygen, carbon, and at least one other element. Sodium carbonate, or soda, soda ash, or sal soda (Na2C03), is an example. It is often found in detergents and cleaning products. 

Beryllium is found in emeralds, which are a variety of the mineral beryl. Perhaps the best-known alkaline-earth metal is calcium, an important mineral nutrient found in the human body. Calcium is essential for muscle contraction. Bones are made up of calcium phosphate. Calcium compounds, such as limestone and marble, are common in the Earth s crust. Marble is made almost entirely of pure calcium carbonate. Because marble is hard and durable, it is used in sculptures. 

Fertilizers have potassium, nitrogen, and phosphorus in a form that dissolves easily in water so that plants can absorb them. The potassium in fertilizer is in an ionic compound called potassium carbonate. Two ionic compounds in the fertilizer contain the nitrogen—ammonium nitrate and ammonium sulfate. The phosphorus supplied is in another ionic compound, calcium dihydrogen phosphate. 

Flame retardant polyurethanes are mostly manufactured with compounds of phosphorus, such as ammonium phosphate or polyphosphate. Aluminum hydroxide alone or in combination with melamine is an alternate approach. In intumescent applications, graphite is frequently used. Calcium carbonate is useful as a flame retarding additive, in combination with other flame retarding materials, because of its large endothennic peak found in DTA curves. ... 

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