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The most common biogenic phosphate is hydroxyapatite (HA), a calcium phosphate (Ca 10 (PO 4) 6 (OH) 2) and a naturally occurring form of apatite. It is a primary constituent of bone, teeth, and fish scales. [33] Bone is made primarily of HA crystals interspersed in a collagen matrix—65 to 70% of the mass of bone is HA.
In some cases their internal organs are replicated in phosphate. The phosphate mainly comes from the tissue itself, and may later be replaced by calcium carbonate. [2] A low pH makes CaCO 3 less likely to precipitate, clearing the way for phosphate to be laid down. [2] This is facilitated by the absence of oxygen in the decaying tissue.
The impacts of reduced calcium carbonate saturation on marine calcifiers have broader ecological implications, as these organisms play vital roles in marine ecosystems. For example, coral reefs, which are built by coral polyps secreting calcium carbonate skeletons, are particularly vulnerable to changes in calcium carbonate saturation. [14]
Microbiologically induced calcium carbonate precipitation (MICP) is a bio-geochemical process that induces calcium carbonate precipitation within the soil matrix. [1] Biomineralization in the form of calcium carbonate precipitation can be traced back to the Precambrian period. [ 2 ]
The term calcium phosphate refers to a family of materials and minerals containing calcium ions (Ca 2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well. Calcium phosphates are white solids of nutritional value [2] and are found in many living organisms, e.g., bone mineral and tooth ...
The alkali–carbonate reaction is an alteration process first suspected in the 1950s in Canada for the degradation of concrete containing dolomite aggregates. [ 1 ] [ 2 ] Alkali from the cement might react with the dolomite crystals present in the aggregate inducing the production of brucite , (MgOH) 2 , and calcite (CaCO 3 ).
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
Calcium hydroxide, Ca(OH) 2, is a strong base, though not as strong as the hydroxides of strontium, barium or the alkali metals. [17] All four dihalides of calcium are known. [18] Calcium carbonate (CaCO 3) and calcium sulfate (CaSO 4) are particularly abundant minerals. [19]