Calcium bicarbonate

Calcium bicarbonate, also called calcium hydrogen carbonate, has a chemical formula Ca(HCO3)2. The term does not refer to a known solid compound; it exists only in aqueous solution containing the calcium (Ca2+), bicarbonate (HCO
3
), and carbonate (CO2−
3
) ions, together with dissolved carbon dioxide (CO2). The relative concentrations of these carbon-containing species depend on the pH; bicarbonate predominates within the range 6.36–10.25 in fresh water.

All waters in contact with the atmosphere absorb carbon dioxide, and as these waters come into contact with rocks and sediments they acquire metal ions, most commonly calcium and magnesium, so most natural waters that come from streams, lakes, and especially wells, can be regarded as dilute solutions of these bicarbonates. These hard waters tend to form carbonate scale in pipes and boilers and they react with soaps to form an undesirable scum.

Attempts to prepare compounds such as solid calcium bicarbonate by evaporating its solution to dryness invariably yield instead the solid calcium carbonate:[1]

Ca(HCO3)2(aq) → CO2(g) + H2O(l) + CaCO3(s).

Very few solid bicarbonates other than those of the alkali metals except lithium and ammonium ion are known to exist.

The above reaction is very important to the formation of stalactites, stalagmites, columns, and other speleothems within caves, and for that matter, in the formation of the caves themselves. As water containing carbon dioxide (including extra CO2 acquired from soil organisms) passes through limestone or other calcium carbonate-containing minerals, it dissolves part of the calcium carbonate, hence becomes richer in bicarbonate. As the groundwater enters the cave, the excess carbon dioxide is released from the solution of the bicarbonate, causing the much less soluble calcium carbonate to be deposited.

In the reverse process, dissolved carbon dioxide (CO2) in rainwater (H2O) reacts with limestone calcium carbonate (CaCO3) to form soluble calcium bicarbonate (Ca(HCO3)2). This soluble compound is then washed away with the rainwater. This form of weathering is called carbonation.

In medicine, calcium bicarbonate is sometimes administered intravenously to immediately correct the cardiac depressor effects of hypokalemia by increasing calcium concentration in serum, and at the same time, correcting the acid usually present.

Calcium bicarbonate
Calcium bicarbonate
Names
IUPAC name
Calcium hydrogen carbonate
Other names
Cleansing lime
Identifiers
3D model (JSmol)
ChemSpider
Properties
Ca(HCO3)2
Molar mass 162.11464 g/mol
16.1 g/100 mL (0 °C)
16.6 g/100 mL (20 °C)
18.4 g/100 mL (100 °C)
Hazards
Main hazards Irritant
R-phrases (outdated) R36
Flash point Non-Flammable
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

References

  1. ^ http://www.newton.dep.anl.gov/askasci/chem99/chem99492.htm
Austin Area Terminal Railroad

The Austin Area Terminal Railroad (reporting mark AUAR) was a short-line terminal railroad headquartered in Round Rock, Texas.

Austin Western Railroad

The Austin Western Railroad (reporting mark AWRR) is a short-line railroad headquartered in Round Rock, Texas.

AWRR operates a 154.8 miles (249.1 km) line from Llano, Texas, to an interchange with Union Pacific Railroad at Giddings, Texas, with a 6.4 miles (10.3 km) branch from Fairland, Texas, to Marble Falls, Texas. Additional interchanges with the UPRR are at McNeil and Elgin. The line was originally part of the Houston and Texas Central Railway, and later part of the Texas and New Orleans Railroad; it is now owned by Capital Metropolitan Transportation Authority, with whom AWRR has the contract to operate the railroad from September 2007. AWRR traffic includes aggregates, crushed limestone, calcium bicarbonate, lumber, beer, chemicals, plastics, and paper.

AWRR is a subsidiary of the Watco Companies.

In addition, the Austin Steam Train Association operates an excursion train between Austin, Texas, Cedar Park, Texas, and Burnet, Texas.

Bicarbonate

In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula HCO−3.

Bicarbonate serves a crucial biochemical role in the physiological pH buffering system.The term "bicarbonate" was coined in 1814 by the English chemist William Hyde Wollaston. The prefix "bi" in "bicarbonate" comes from an outdated naming system and is based on the observation that there is twice as much carbonate (CO2−3) per sodium ion in sodium bicarbonate (NaHCO3) and other bicarbonates than in sodium carbonate (Na2CO3) and other carbonates. The name lives on as a trivial name.

According to the Wikipedia article IUPAC nomenclature of inorganic chemistry, the prefix bi– is a deprecated way of indicating the presence of a single hydrogen ion. The recommended nomenclature today mandates explicit referencing of the presence of the single hydrogen ion: sodium hydrogen carbonate or sodium hydrogencarbonate. A parallel example is sodium bisulfite (NaHSO3).

Caecobarbus

Caecobarbus geertsi, the African blind barb or Congo blind barb (known as Nzonzi a mpofo in the local Kikongo language, meaning blind barb), is a species of cyprinid fish. This threatened cavefish is only known from Democratic Republic of the Congo, and it is the only member of the monotypic genus Caecobarbus. It was George Albert Boulenger who described this fish in 1921 and it completely lacks close relatives in the Congo region.Despite its common name, "African blind barb," there are other blind cave cyprinids indigenous to Africa, notably the Somalian Barbopsis devecchi and Phreatichthys andruzzii.

Calcium carbonate

Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks as the minerals calcite and aragonite (most notably as limestone, which is a type of sedimentary rock consisting mainly of calcite) and is the main component of pearls and the shells of marine organisms, snails, and eggs. Calcium carbonate is the active ingredient in agricultural lime and is created when calcium ions in hard water react with carbonate ions to create limescale. It is medicinally used as a calcium supplement or as an antacid, but excessive consumption can be hazardous.

Carbonic acid

Not to be confused with carbolic acid, an antiquated name for phenol.Carbonic acid is a chemical compound with the chemical formula H2CO3 (equivalently: OC(OH)2). It is also a name sometimes given to solutions of carbon dioxide in water (carbonated water), because such solutions contain small amounts of H2CO3. In physiology, carbonic acid is described as volatile acid or respiratory acid, because it is the only acid excreted as a gas by the lungs. It plays an important role in the bicarbonate buffer system to maintain acid–base homeostasis.

Carbonic acid, which is a weak acid, forms two kinds of salts: the carbonates and the bicarbonates. In geology, carbonic acid causes limestone to dissolve, producing calcium bicarbonate, which leads to many limestone features such as stalactites and stalagmites.

It was long believed that carbonic acid could not exist as a pure compound. However, in 1991 it was reported that NASA scientists had succeeded in making solid H2CO3 samples.

Cypripedium acaule

Cypripedium acaule is a member of the orchid genus Cypripedium. Members of this genus are commonly referred to as lady's slipper orchids. First described in 1789 by Scottish botanist William Aiton, C. acaule is commonly referred to as the pink lady's slipper, stemless lady's-slipper, or moccasin flower. The pink lady's slipper is the provincial flower of Prince Edward Island, Canada and the state wildflower of New Hampshire, United States. Its close relative, Cypripedium reginae, is the state flower of Minnesota.

Hard water

Hard water is water that has high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone, chalk or gypsum which are largely made up of calcium and magnesium carbonates, bicarbonates and sulfates.

Hard drinking water may have moderate health benefits, but can pose critical problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling towers, and other equipment that handles water. In domestic settings, hard water is often indicated by a lack of foam formation when soap is agitated in water, and by the formation of limescale in kettles and water heaters. Wherever water hardness is a concern, water softening is commonly used to reduce hard water's adverse effects.

Indiana Caverns

Indiana Caverns is part of the Binkley Cave system near Corydon, Indiana.

Ink

Ink is a liquid or paste that contains pigments or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing or writing with a pen, brush, or quill. Thicker inks, in paste form, are used extensively in letterpress and lithographic printing.

Ink can be a complex medium, composed of solvents, pigments, dyes, resins, lubricants, solubilizers, surfactants, particulate matter, fluorescents, and other materials. The components of inks serve many purposes; the ink's carrier, colorants, and other additives affect the flow and thickness of the ink and its dry appearance.

In 2011 worldwide consumption of printing inks generated revenues of more than 20 billion US dollars. Demand by traditional print media is shrinking, on the other hand more and more printing inks are consumed for packagings.

Limescale

Limescale is a hard, off-white, chalky deposit often found in kettles and hot water boilers and on the inside of hot water pipework. It is also often found as a similar deposit on the inner surfaces of old pipes and other surfaces where "hard water" has evaporated.

In addition to being unsightly and hard to clean, limescale can seriously damage or impair the operation of various plumbing and heating components. Descaling agents are commonly used to remove limescale. Prevention of fouling by scale build-up relies on the technologies of water softening.

Limewater

Limewater is the common name for a dilute aqueous solution of calcium hydroxide. Calcium hydroxide, Ca(OH)2, is sparsely soluble at room temperature in water

(1.5 g/L at 25 °C).

"Pure" (i.e. less than or fully saturated) limewater is clear and colorless, with a slight earthy smell and an astringent/bitter taste. It is basic in nature with a pH of 12.4.

Limewater may be prepared by mixing calcium hydroxide (Ca(OH)2) with water and removing excess undissolved solute (e.g. by filtration).

When excess calcium hydroxide is added (or when environmental conditions are altered, e.g. when its temperature is raised sufficiently),

a milky solution results due to the homogeneous suspension of excess calcium hydroxide. This liquid has been known traditionally as milk of lime.

Magnesium bicarbonate

Magnesium bicarbonate or magnesium hydrogen carbonate, Mg(HCO3)2, is the bicarbonate salt of magnesium. It can be formed through the reaction of dilute solutions of carbonic acid (such as seltzer water) and magnesium hydroxide (milk of magnesia).

It can be prepared through the synthesis of Magnesium acetate and Sodium bicarbonate

Mg(CH3COO)2 + 2NaHCO3 = Mg(HCO3)2 + 2CH3COONa

Magnesium bicarbonate exists only in aqueous solution. Magnesium does not form solid bicarbonate as like Lithium. To produce it, a suspension of magnesium hydroxide is treated with pressurized carbon dioxide, producing a solution of magnesium bicarbonate:

Mg(OH)2 + 2 CO2 → Mg(HCO3)2Drying the resulting solution causes the magnesium bicarbonate to decompose, yielding magnesium carbonate, carbon dioxide, and water:

Mg2+ + 2 HCO3− → MgCO3 + CO2 + H2O

Meshkat

Meshkat (Persian: مشكات‎, pronounced /meʃ'ka:t/ with stress on second syllable; also known as Moshkān, Mashgān, and Mashkān) is a city in the Central District of Kashan County, Isfahan Province, Iran. At the 2016 census, its population was 5,357, in 1,687 families.

Speleogenesis

Speleogenesis is the origin and development of caves, the primary process that determines essential features of the hydrogeology of karst and guides its evolution. It often deals with the development of caves through limestone, caused by the presence of water with carbon dioxide dissolved within it, producing carbonic acid which permits the dissociation of the calcium carbonate in the limestone.

Stalactite

A stalactite (UK: , US: ; from the Greek stalasso, (σταλάσσω), "to drip", and meaning "that which drips") is a type of formation that hangs from the ceiling of caves, hot springs, or manmade structures such as bridges and mines. Any material that is soluble, can be deposited as a colloid, or is in suspension, or is capable of being melted, may form a stalactite. Stalactites may be composed of lava, minerals, mud, peat, pitch, sand, sinter, and amberat (crystallized urine of pack rats). A stalactite is not necessarily a speleothem, though speleothems are the most common form of stalactite because of the abundance of limestone caves.The corresponding formation on the floor of the cave is known as a stalagmite. Mnemonics have been developed for which word refers to which type of formation; one is that stalactite has a C for "ceiling", and stalagmite has a G for "ground".

Stalagmite

A stalagmite (UK: or US: ; from the Greek σταλαγμίτης – stalagmitês, from σταλαγμίας – stalagmias, "dropping, trickling")

is a type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings. Stalagmites may be composed of lava, minerals, mud, peat, pitch, sand, sinter and amberat (crystallized urine of pack rats).The corresponding formation hanging down from the ceiling of a cave is a stalactite. Mnemonics have been developed for which word refers to which type of formation; one is that stalactite has a C for "ceiling", and stalagmite has a G for "ground".

Thomas Clark (chemist)

Thomas Clark (1801–1867) was a Scottish chemist.He became known for the discovery of the phosphate of soda, and the process of lime softening of hard water the 'Clark process'. A Clark degree (°Clark) of water hardness is defined as one grain (64.8 mg) of CaCO3 per Imperial gallon (4.55 litres) of water, equivalent to 14.254 ppm. and 10^5 parts of water

Weathering

Weathering is the breaking down of rocks, soil, and minerals as well as wood and artificial materials through contact with the Earth's atmosphere, water, and biological organisms. Weathering occurs in situ (on site), that is, in the same place, with little or no movement, and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, snow, wind, waves and gravity and then being transported and deposited in other locations.

Two important classifications of weathering processes exist – physical and chemical weathering; each sometimes involves a biological component. Mechanical or physical weathering involves the breakdown of rocks and soils through direct contact with atmospheric conditions, such as heat, water, ice and pressure. The second classification, chemical weathering, involves the direct effect of atmospheric chemicals or biologically produced chemicals also known as biological weathering in the breakdown of rocks, soils and minerals. While physical weathering is accentuated in very cold or very dry environments, chemical reactions are most intense where the climate is wet and hot. However, both types of weathering occur together, and each tends to accelerate the other. For example, physical abrasion (rubbing together) decreases the size of particles and therefore increases their surface area, making them more susceptible to chemical reactions. The various agents act in concert to convert primary minerals (feldspars and micas) to secondary minerals (clays and carbonates) and release plant nutrient elements in soluble forms.

The materials left over after the rock breaks down combined with organic material creates soil. The mineral content of the soil is determined by the parent material; thus, a soil derived from a single rock type can often be deficient in one or more minerals needed for good fertility, while a soil weathered from a mix of rock types (as in glacial, aeolian or alluvial sediments) often makes more fertile soil. In addition, many of Earth's landforms and landscapes are the result of weathering processes combined with erosion and re-deposition.

Calcium compounds

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