Calcium reactivity

Keller, J.N., Hanni, K.B., Markesbery, W.R., 1999, Oxidized low-density hpoprotein induces neuronal death impheations for calcium, reactive oxygen spedes, and caspases, Neurochem, 72 2601-2609. 

Munro et al. showed separation and detection of amino acids on microchips using an indirect fluorescence detection method. Figure 36.10 shows application of this method to urine samples with no pretreatment other than dilution in the appropriate separation buffer. Abnormal amounts of amino acids can easily be detected in the two patient samples compared to the healthy control sample. An absorbance detection based approach was utilized for the clinical analysis of calcium ion in serum, which is important in the regulation of a number of physiological processes. Beads with an immobilized calcium reactive dye were placed into the detection region, and the samples mobilized past the beads using electrophoretic flow. While a true separation was not intended, the interference... 

As with other rare-earth metals, except for lanthanum, europium ignites in air at about 150 to I8O0C. Europium is about as hard as lead and is quite ductile. It is the most reactive of the rare-earth metals, quickly oxidizing in air. It resembles calcium in its reaction with water. Bastnasite and monazite are the principal ores containing europium. 

Although stable at ambieat temperature, calcium fluoride is slowly hydrolyzed by moist air at about 1200°C, presumably to CaO and HF. Calcium fluoride is not attacked by alkahes or by reactive fluorine compounds, but is decomposed by hot, high boiling acids, as ia the reactioa with coaceatrated sulfuric acid which is the process used to produce hydrogea fluoride. Calcium fluoride is slightly soluble ia cold dilute acids, and somewhat more soluble ia solutioas of alumiaum hahdes. 

Properties. Lithium fluoride [7789-24-4] LiF, is a white nonhygroscopic crystaUine material that does not form a hydrate. The properties of lithium fluoride are similar to the aLkaline-earth fluorides. The solubility in water is quite low and chemical reactivity is low, similar to that of calcium fluoride and magnesium fluoride. Several chemical and physical properties of lithium fluoride are listed in Table 1. At high temperatures, lithium fluoride hydroly2es to hydrogen fluoride when heated in the presence of moisture. A bifluoride [12159-92-17, LiF HF, which forms on reaction of LiF with hydrofluoric acid, is unstable to loss of HF in the solid form. 

OtherAlkaline-Parth Hydrides. Strontium and barium hydrides resemble calcium hydride in properties and reactivity. They have no significant commercial apphcations. 

Suitable catalysts include the hydroxides of sodium (119), potassium (76,120), calcium (121—125), and barium (126—130). Many of these catalysts are susceptible to alkali dissolution by both acetone and DAA and yield a cmde product that contains acetone, DAA, and traces of catalyst. To stabilize DAA the solution is first neutralized with phosphoric acid (131) or dibasic acid (132). Recycled acetone can then be stripped overhead under vacuum conditions, and DAA further purified by vacuum topping and tailing. Commercial catalysts generally have a life of about one year and can be reactivated by washing with hot water and acetone (133). It is reported (134) that the addition of 0.2—2 wt % methanol, ethanol, or 2-propanol to a calcium hydroxide catalyst helps prevent catalyst aging. Research has reported the use of more mechanically stable anion-exchange resins as catalysts (135—137). The addition of trace methanol to the acetone feed is beneficial for the reaction over anion-exchange resins (138). 

Except for dead-burned dolomite, all limes are much more reactive with acids than limestone. The high calcium types are the most reactive. 

The chemical properties of strontium are intermediate between those of calcium and barium. Strontium is more reactive than calcium, less reactive than barium. Strontium is bivalent and reacts with to form SrH2 [13598-33-9] at reasonable speed at 300—400°C. It reacts with H2O, O2, N2, F, S, and... 

Potassium peroxymonosulfate, introduced in the late 1980s, is finding increasing use as an auxiUary oxidant for shock treatment and oxidation of chloramines. Sodium peroxydisulfate is also being sold for shock treatment, however, it is less reactive than peroxymonosulfate. Mixtures of sodium peroxydisulfate and calcium hypochlorite can be used for shock treatment (28). Disadvantages of peroxymonosulfate and peroxydisulfate are they do not provide a disinfectant residual and peroxymonosulfate oxidizes urea and chloramines to nitrate ion, which is a nutrient for algae. 

Barium reduces the oxides, haUdes, and sulfides of most of the less reactive metals, thereby producing the corresponding metal. It has reportedly been used to prepare metallic americium via reduction of americium trifluoride (13). However, calcium metal can, in most cases, be used for similar purposes and is usually preferred over barium because of lower cost per equivalent weight and nontoxicity (see Actinides and transactinides). 

Because of its high reactivity, production of barium by such processes as electrolysis of barium compound solution or high temperature carbon reduction is impossible. Electrolysis of an aqueous barium solution yields Ba(OH)2, whereas carbon reduction of an ore such as BaO produces barium carbide [50813-65-5] BaC2, which is analogous to calcium carbide (see Carbides). Attempts to produce barium by electrolysis of molten barium salts, usually BaCl25 met with only limited success (14), perhaps because of the solubiUty of Ba in BaCl2 (1 )-... 

Because of its extreme chemical reactivity, calcium metal must be carefully packaged for shipment and storage. The metal is packaged in sealed argon-tiUed containers. Calcium is classed as a flammable soHd and is nonmailable. Sealed quantities of calcium should be stored in a dry, weU-ventilated area so as to remove any hydrogen formed by reaction with moisture. 

---