Barium chemistry

Lying just below barium in the periodic table, radiums chemistry is essentially identical to bariums chemistry. In fact, there is a famous story in which confusion between the two elements played an important role. In the 1930s, Italian physicist Enrico Fermi (1901-54) and his coworkers were investigating the action of neutrons on samples of uranium. (The neutron had only been discovered in 1930. Its use in physics was still relatively new.) Their expectation was that the absorption of neutrons by uranium would lead to the production of transuranium elements (elements lying beyond uranium in the periodic table), as shown by the following equation ... 

This is a radioactive element. It occurs in minute traces in barium and thorium minerals, but it can be produced by irradiation of bismuth in a nuclear reactor. (The study of its chemistry presents great difficulty because of its intense a radiation). 

The most stable protected alcohol derivatives are the methyl ethers. These are often employed in carbohydrate chemistry and can be made with dimethyl sulfate in the presence of aqueous sodium or barium hydroxides in DMF or DMSO. Simple ethers may be cleaved by treatment with BCI3 or BBr, but generally methyl ethers are too stable to be used for routine protection of alcohols. They are more useful as volatile derivatives in gas-chromatographic and mass-spectrometric analyses. So the most labile (trimethylsilyl ether) and the most stable (methyl ether) alcohol derivatives are useful in analysis, but in synthesis they can be used only in exceptional cases. In synthesis, easily accessible intermediates of medium stability are most helpful. 

In general, the chemistry of inorganic lead compounds is similar to that of the alkaline-earth elements. Thus the carbonate, nitrate, and sulfate of lead are isomorphous with the corresponding compounds of calcium, barium, and strontium. In addition, many inorganic lead compounds possess two or more crystalline forms having different properties. For example, the oxides and the sulfide of bivalent lead are frequendy colored as a result of their state of crystallisation. Pure, tetragonal a-PbO is red pure, orthorhombic P PbO is yeUow and crystals of lead sulfide, PbS, have a black, metallic luster. 

Chemical scaling is another form of fouling that occurs in NF and RO plants. The thermodynamic solubility of salts such as calcium carbonate and calcium and barium sulfate imposes an upper boundary on the system recovery. Thus, it is essential to operate systems at recoveries lower than this critical value to avoid chemical scaling, unless the water chemistry is adjusted to prevent precipitation. It is possible to increase system recovery by either adjusting the pH or adding an antisealant, or both. 

Jongen, N., Lemaitre, J., Bowen, P. and Hofmann, H., 1999. Aqueous synthesis of mixed yttrium-barium oxalates. Chemistry of Materials, 11, pp. 712-718. 

W. E. Lindsell in Structure oj Magnesium, Calcium, Strontium, and Barium Compounds in Comprehensive Organometallic Chemistry, G. Wilkinson. F. G. A. Stone, E. W. Abel. Eds., Vol. 1. pp 155-252. Pergamon, Oxford 1982. 

Some acrylic acid copolymers are promoted as having a very wide range of functions that permit them to act as calcium phosphate DCAs, barium sulfate antiprecipitants, particulate iron oxides dispersants, and colloidal iron stabilizers. One such popular copolymer is acrylic acid/sulfonic acid (or acrylic acid/ 2-acrylamido-methylpropane sulfonic acid, AA/SA, AA/AMPS). Examples of this chemistry include Acumer 2000 (4,500 MW) 2100 (11,000 MW) Belclene 400, Acrysol QR-1086, TRC -233, and Polycol 43. 

Recognition among bone-chemistry researchers that strontium enters bone in proportion to dietary levels has resulted in widely accepted yet erroneous inferences about the relationships among various elements in bone and past diet. One such inference is that more of any element in the diet translates directly to more of that element in bone. If an element is not biogenically incorporated within bone, or if biological levels are metabolically controlled, then that element will not reflect diet. A second erroneous inference is that strontium can be used to measure the dietary plant/meat ratio. Sr/Ca ratios in meat are generally lower than those of plants, but meat is also low in calcium and hence has little effect on the composition of bone. Plants, on the other hand, contribute substantially to bone composition. Variations in the strontium levels of bone thus more likely reflect differential consumption of plants rather than trophic position. Although efforts to determine plant/meat ratios from strontium and to draw dietary inferences from elements other than strontium and barium have not been successful, this failure has been due to inappropriate expectations, not to a failure of bone strontium to reflect diet. 

One of the most exciting developments in materials science in recent years involves mixed oxides containing rare earth metals. Some of these compounds are superconductors, as described in our Chemistry and Technology Box. Below a certain temperature, a superconductor can carry an immense electrical current without losses from resistance. Before 1986, it was thought that this property was limited to a few metals at temperatures below 25 K. Then it was found that a mixed oxide of lanthanum, barium, and copper showed superconductivity at around 30 K, and since then the temperature threshold for superconductivity has been advanced to 135 K. 

The use of sterically bulky ligands to provide kinetic stability to compounds of the heavier group 2 elements has become widely practiced, and has facilitated the synthesis of diorganyl complexes of various types. Advances in the organometallic chemistry of bonded compounds of calcium, strontium, and barium have been reviewed. 

Beryllium and magnesium belong to the 2nd group of the Periodic Table together with calcium, strontium, barium and radium. Characteristic differences, however, may be noticed between the chemistry of Be and Mg and that of the alkaline earth s proper. Be has a unique chemical behaviour with a predominantly covalent character. The heavier elements (Ca, Sr, Ba, Ra) have a predominant ionic behaviour in their compounds. Mg has a chemistry in a way intermediate but closer to that of Be. Analogies between the Mg and Zn chemistries may also be underlined. 

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