Calcium chemical properties

Selective Reduction. In aqueous solution, europium(III) [22541 -18-0] reduction to europium(II) [16910-54-6] is carried out by treatment with amalgams or zinc, or by continuous electrolytic reduction. Photochemical reduction has also been proposed. When reduced to the divalent state, europium exhibits chemical properties similar to the alkaline-earth elements and can be selectively precipitated as a sulfate, for example. This process is highly selective and allows production of high purity europium fromlow europium content solutions (see Calcium compounds Strontiumand strontium compounds). 

Strontium [7440-24-6] Sr, is in Group 2 (IIA) of the Periodic Table, between calcium and barium. These three elements are called alkaline-earth metals because the chemical properties of the oxides fall between the hydroxides of alkaU metals, ie, sodium and potassium, and the oxides of earth metals, ie, magnesium, aluminum, and iron. Strontium was identified in the 1790s (1). The metal was first produced in 1808 in the form of a mercury amalgam. A few grams of the metal was produced in 1860—1861 by electrolysis of strontium chloride [10476-85-4]. 

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... 

Many other metal thiosulfates, eg, magnesium thiosulfate [10124-53-5] and its hexahydrate [13446-30-5] have been prepared on a laboratory scale, but with the exception of the calcium, barium [35112-53-9] and lead compounds, these are of Httle commercial or technical interest. Although thaHous [13453-46-8] silver, lead, and barium thiosulfates are only slightly soluble, other metal thiosulfates are usually soluble in water. The lead and silver salts are anhydrous the others usually form more than one hydrate. Aqueous solutions are stable at low temperatures and in the absence of air. The chemical properties are those of thiosulfates and the respective cation. 

Physical and Chemical Properties. Because of decomposition, the melting point of calcium cyanide can only be estimated by extrapolation to be 640°C (70). 

The side chains of the 20 different amino acids listed in Panel 1.1 (pp. 6-7) have very different chemical properties and are utilized for a wide variety of biological functions. However, their chemical versatility is not unlimited, and for some functions metal atoms are more suitable and more efficient. Electron-transfer reactions are an important example. Fortunately the side chains of histidine, cysteine, aspartic acid, and glutamic acid are excellent metal ligands, and a fairly large number of proteins have recruited metal atoms as intrinsic parts of their structures among the frequently used metals are iron, zinc, magnesium, and calcium. Several metallo proteins are discussed in detail in later chapters and it suffices here to mention briefly a few examples of iron and zinc proteins. 

Other actions of estrogen include fluid retention, protein anabolism, thinning of the cervical mucus, and the inhibition or facilitation of ovulation. Estrogens contribute to the conservation of calcium and phosphorus, the growth of pubic and axillary hair, and pigmentation of the breast nipples and genitals. Estrogens also stimulate contraction of the fallopian tubes (which promotes movement of the ovum), modify the physical and chemical properties of the cervical mucus, and restore the endometrium after menstruation. 

The chemical properties of copper, lead, lead-zinc, and zinc slags are essentially as ferrous silicates, whereas nickel slags are primarily calcium/magnesium silicates. Table 4.13 lists typical chemical compositions of these slags. 

Many other fuels such as soot, turf, corkmeal, powdered anthracite, woodmeal, carbene (polymerized acetylene), calcium hydride, and spongy aluminum have been tried. Physical and chemical properties of many LOX fuels are given by Howell et al (Ref 3) and O Neil Van Fleet (Ref 5a)... 

Carstensen JT, Ertell C. Physical and chemical properties of calcium phosphates for solid state pharmaceutical formulations. Drug Dev Ind Pharma 1990 16 1121-1133. 

Calcium is readily absorbed by the body for the building of bones. Since calcium and strontium are in the same atomic group, they have similar physical and chemical properties. The body, therefore, has a hard time distinguishing between the two and strontium is absorbed just as though it were calcium. 

Herrington, B. L. 1934B. Some physico-chemical properties of lactose. VI. The solubility of lactose in salt solutions the isolation of a compound of lactose and calcium chloride. J. Dairy Sci. 17, 805-814. 

Fuchs, F. Chemical properties of the calcium receptor site of troponin as determined from binding studies. In Calcium binding proteins (eds. W. Drabikowski, H. Strzelecka-Golaszewska and E. Carafoli), pp. 1-27. Amsterdam Elsevier Scientific Publ. and Warszawa PWN-Polish Scientific Publ. 1974. 

Herring, G. M., Andrews, A. T. de B., and Chipperfield, A. R. Chemical structure of bone sialoprotein and a preliminary study of its calcium-binding properties. In Cellular mechanisms for calcium transfer and homeostasis (eds. G. Nichols, Jr. and R. H. Wasserman), pp. 63-73. New York and London Academic Press 1971. 

However, other scientists had also attempted to categorise the known elements. In 1817, Johann Dobereiner noticed that the atomic weight (now called atomic mass) of strontium fell midway between the weights of calcium and barium. These were elements which possessed similar chemical properties. They formed a triad of elements. Other triads were also discovered, composed of ... 

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