Calcium limitation

Other chronic disorders cause osteomalacia. " " Phosphate depletion from low dietary intake, phosphate-binding antacids, and oncogenic osteomalacia (potentially phosphaturic effect) can cause osteomalacia. Hypophosphatasia is an inborn error of metabolism in which deficient activity of alkaline phosphatase causes impaired mineralization of bone matrix. Acidosis from renal dysfunction, distal renal tubular acidosis, hypergammaglobulinemic states (e.g., multiple myeloma), and drugs (e.g., chemotherapy) compromises bone mineralization. Renal tubular disorders secondary to Fanconi s syndrome, hereditary diseases (e.g., Wilson s disease, a defect in copper metabolism), acquired disease (e.g., myeloma), and toxins (e.g., lead) cause osteomalacia to varying degrees. Chronic wastage of phosphorus and/or calcium limits mineralization, which may be further compromised by acidosis and secondary hyperparathyroidism. 

Another valuable drying agent of general application is anhydrous calcium sulphate, marketed under the name of Drierite. It is rapid in its action, but has only a limited drying capacity because it forms the hydrate 2CaS04,H20 and thus combines with only 6-6 per cent, of its weight of water. The vapour pressure of the system ... 

Historically, the use of acetylene as raw material for chemical synthesis has depended strongly upon the avadabihty of alternative raw materials. The United States, which until recendy appeared to have limitless stocks of hydrocarbon feeds, has never depended upon acetylene to the same extent as Germany, which had more limited access to hydrocarbons (1). During Wodd War 1 the first manufacture of a synthetic mbber was undertaken ia Germany to replace imported natural mbber, which was no longer accessible. Acetylene derived from calcium carbide was used for preparation of... 

Israel Mining Industries developed a process in which hydrochloric acid, instead of sulfuric acid, was used as the acidulant (37). The acidulate contained dissolved calcium chloride which then was separated from the phosphoric acid by use of solvent extraction using a recyclable organic solvent. The process was operated commercially for a limited time, but the generation of HCl fumes was destmctive to production equipment. 

Barium fluoride is used commercially in combination with other fluorides for arc welding (qv) electrode fluxes. However, this usage is limited because of the availabiUty of the much less expensive naturally occurring calcium fluoride. 

The large amount of fluorine values released from phosphate rock in the manufacture of fertilisers (qv) gives a strong impetus to develop fluorine chemicals production from this source (see Phosphoric acid and the phosphates). Additional incentive comes from the need to control the emission of fluorine-containing gases. Most of the fluorine values are scmbbed out as fluorosiUcic acid, H2SiPg, which has limited useflilness. A procedure to convert fluorosihcic acid to calcium fluoride is available (61). 

Health and Safety Factors. The low solubiUty of calcium fluoride reduces the potential problem of fluoride-related toxicity. Water saturated with calcium fluoride has a fluoride concentration of 8.1 ppm as compared to the recommended water fluoridation level of 1 ppm fluoride ion. However, because the solubiUty of calcium fluoride ia stomach acid is higher, continued oral ingestion of calcium fluoride could produce symptoms of fluorosis. The adopted TWA limit for fluorides as F is 2.5 mg/m (68,69). 

The rate of dissolution is limited by oxygen availabiUty rather than by cyanide concentration. When oxygen solubiUty is reduced by water salinity or by consumption by ore constituents such as sulfide minerals, enrichment of the air with oxygen or addition of hydrogen or calcium peroxide improves leaching kinetics and decreases cyanide consumption (10). 

Rigid Applications. The use of the lead stabilizers is very limited in the United States but, they are stiU used in several rigid PVC appHcations in Europe and Asia. The highest use of lead stabilizers in rigid PVC is for pipe and conduit appHcations. Tribasic lead sulfate is the primary heat stabilizer with lead stearates included to provide lubrication. The lead products are typically fully formulated, usually including lubricants and pigments for pipe extmsion appHcations. These lead one-packs, when used at about 1.8—2.5 phr, provide all of the stabilizer and lubrication needed to process the polymer. A lead one-pack contains tribasic lead sulfate, dibasic lead stearate calcium stearate, polyethylene wax, paraffin wax, ester wax, and pigments. 

Lactic acid is generally recognized as safe (GRAS) for multipurpose food use. Lactate salts such as calcium and sodium lactates and esters such as ethyl lactate used in pharmaceutical preparations are also considered safe and nontoxic (7). The U.S. Food and Dmg Administration fists lactic acid (all isomers) as GRAS and sets no limitations on its use in food other than current good manufacturing practice (46). 

Alkali metal haHdes can be volatile at incineration temperatures. Rapid quenching of volatile salts results in the formation of a submicrometer aerosol which must be removed or else exhaust stack opacity is likely to exceed allowed limits. Sulfates have low volatiHty and should end up in the ash. Alkaline earths also form basic oxides. Calcium is the most common and sulfates are formed ahead of haHdes. Calcium carbonate is not stable at incineration temperatures (see Calcium compounds). Transition metals are more likely to form an oxide ash. Iron (qv), for example, forms ferric oxide in preference to haHdes, sulfates, or carbonates. SiHca and alumina form complexes with the basic oxides, eg, alkaH metals, alkaline earths, and some transition-metal oxidation states, in the ash. 

Direct Metal Analyses. Calcium ion can be detected to a lower limit of 10 M hy Aequorea bioluminescence. Strontium interferes to a minor extent (270,271). 

Maleic Anhydride. The ACGIH threshold limit value in air for maleic anhydride is 0.25 ppm and the OSHA permissible exposure level (PEL) is also 0.25 ppm (181). Maleic anhydride is a corrosive irritant to eyes, skin, and mucous membranes. Pulmonary edema (collection of fluid in the lungs) can result from airborne exposure. Skin contact should be avoided by the use of mbber gloves. Dust respirators should be used when maleic anhydride dust is present. Maleic anhydride is combustible when exposed to heat or flame and can react vigorously on contact with oxidizers. The material reacts exothermically with water or steam. Violent decompositions of maleic anhydride can be catalyzed at high temperature by strong bases (sodium hydroxide, potassium hydroxide, calcium hydroxide, alkaU metals, and amines). Precaution should be taken during the manufacture and use of maleic anhydride to minimize the presence of basic materials. 

Many other recovery alternatives have been proposed that iaclude ion exchange (qv), pyrolysis, and wet combustion. However, these have not gained general acceptance. A limited number of calcium-based mills are able to utilize their spent pulpiag liquors to produce by-products such as lignosulfates for oil-weU drilling muds, vanillin, yeast, and ethyl alcohol (see PETROLEUM Vanillin). 

Carboxylic Acid Group. Sorbic acid undergoes the normal acid reactions forming salts, esters, amides, and acid chlorides. Industrially, the most important compound is the potassium salt because of stabiUty and high water solubiUty. Sodium sorbate [7757-81-5] (E,E form [42788-83-0]) is less stable and not commercially available. The calcium salt [7492-55-9] which has limited solubiUty, has use in packaging (qv) materials. 

Sorbic acid and its potassium salt, collectively called sorbates, are used primarily in a wide range of food and feed products (63) and to a lesser extent in certain cosmetics (64), pharmaceuticals, and tobacco products. There are limited appHcations of the calcium and sodium salts, but the acid and its potassium salt are used almost exclusively. 

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