Barium occurrence

EPA. 1983b. Barium occurrence in drinking water, food, and air. US Environmental Protection Agency, Office of Drinking Water. 

Videman T, Nurminen M (2004) The occurrence of anular tears and their relation to lifetime back pain history a cadaveric study using barium sulfate discography. Spine 29 (23) 2668-2676... 

Occurrence. Barium occurs mainly as witherite (BaC03) and baryte or heavy spar (BaS04). 

Assigning oxidation states of —2 to oxygen, + 3 to yttrium and + 2 to barium, one would obtain an oxidation state 7/3 for copper when jc = 0. The non-integer oxidation state of copper is interpreted as if 2/3 of the ions are present as Cu2+ and 1/3 as Cu3 +. This mixed-valent composition seems to be determinant for the occurrence of superconductivity. In fact, as noted in Table 1, all the superconducting ceramic oxides contain Cu in a non-stoichiometric composition. 

Boissevain CH, Drea WF. 1936. Relation between the occurrence of endemic goiter and the presence of traces of silver and barium in drinking water. Endocrinology 26 686-687. 

Other Systemic Effects. Other systemic effects have been observed. Barium sulfate was observed to act as an appendocolith in two cases following barium enema procedures (Palder and Dalessandri 1988). This is a rare occurrence and probably not significant in cases of human barium toxicity. Intravenous injection of barium sulfate into pigs increased calcitonin secretion from the thyroid (Pento 1979). This is probably not a significant effect for humans since intravenous exposure is not a common route and the dose required was so high (1.7 mg/kg/minute for 20 minutes) it caused cardiotoxicity. 

Barium has been detected with a positive geometric mean concentration of 101.6 mg/L in groundwater samples from approximately 58% of the 2,783 hazardous waste sites that have had samples analyzed by the Contract Laboratory Program (CLP) (CLPSD 1989). Barium has also been detected with a positive geometric mean of 62.6 mg/L in surface water samples from 27% of the sites in the CLP statistical database (CLPSD) represent frequency of occurrence and concentration information for NPL sites only. 

Solubility of sparingly soluble salts of weak acids in strong mineral acids The solubility product principle enables us to give a simple explanation of this phenomenon, which is of relatively frequent occurrence in quantitative analysis. Typical examples are the solubilities of calcium oxalate or barium carbonate in hydrochloric acid. When dilute hydrochloric acid is added to a suspension of calcium oxalate, the following equilibria will occur simultaneously ... 

MAGNESIUM, CALCIUM, STRONTIUM, BARIUM, AND RADIUM 4-6 Occurrence The Elements... 

Ca) (iii) the nuclear statistical equilibrium peak at the position of Fe and (iv) the abundance peaks in the region past iron at the neutron closed shell positions (zirconium, barium, and lead), confirming the occurrence of processes of neutron-capture synthesis. The solar system abundance patterns associated specifically with the slow (s-process) and fast (r-process) processes of neutron capture synthesis are shown in Figure 2. 

A similar analytical scheme for following the transformation of 3,4,6-tri-O-methyl-D-fructose gave somewhat better results. In these experiments, the disappearance of 3,4,6-tri-O-methyl-n-fructose was determined by measuring the formaldehyde released on periodate oxidation. The periodate consumption by these mixtures served as a check on the formation of products other than 3,4,6-tri-0-methyl-n-glucose and 3,4,6-tri-O-methyl-D-mannose, since each of the 3,4,6-tri-O-methylhexoses consumes 1 mole of periodate per mole. Actually, the periodate titers increased approximately 20% during the time-period that the apparent concentration of 3,4,6-tri-O-methyl-D-fructose diminished to about 60% of the initial concentration (when the reaction was carried out in sodium hydroxide solution). The change in periodate consumed was attributed to occurrence of demethylation. When the transformation was carried out in either calcium hydroxide or barium hydroxide solutions, the periodate consumption increased markedly. Hence, calcium and barium ions appear to catalyze this side reaction. ... 

In this chapter, the reader will learn about the nucleosynthesis of strontium and barium, the occurrence of both elements on Earth, the chemistry of both elements, and their practical applications. 

BERYLLIUM AND THE GROUP II elements Mg, Ca, Sr, Ba, Ra 215 MAGNESIUM, CALCIUM, STRONTIUM, BARIUM AND RADIUM 7-8. Occurrence the Elements... 

The penta-, selenopenta-, and telluropentathionate ions have mirror plane symmetry in the crystals. This is crystallographically required in all four structure types except the triclinic one, but is realized even there. The ions thus have a cis form in these salts, with the terminal sulfonate groups on the same side of the plane through the three middle atoms. The occurrence of the cis form in the barium salts is perhaps due to the oxygencoordinating power of the barium ion, and favorable lattice conditions for the mirror-plane cis arrangement. 

The radius of the Ba " -ion is 135 pm, which is close to that of potassium ion (K" " 138 pm) (Greenwood and Earnshaw 1988). This similar ionic size is the reason for the occurrence of barium in potassium feldspar and biotite (Rosier 1991). 

Dey S, Varman R, Chakravarty A and Bhatta-CHARYA M (1993) The occurrence of barium in the corneal surface of the barking deer, Muntiacus muntjak (Zimmermann) as revealed by energy dispersive X-ray micro-analysis. Micron 24 451-455. 

Robinson WO, Whetstone RR and Edington G (1950) The occurrence of barium in soils and plants. United States Department Agriculture Technical Bulletin 1013 1-36. 

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