Strontium, illustration

Samples of animal bones weighing approximately 3 g are ashed at 600 °C until the entire bone is ash-white. Samples are then crushed in a mortar and pestle. A portion of the sample is digested in HCl and diluted to a known volume. The concentrations of zinc and strontium are determined by atomic absorption. The analysis for strontium illustrates the use of a protecting agent as La(N03)3 is added to prevent an interference due to the formation of refractory strontium phosphate. 

Since aldehydes are notoriously polymerizable and difficult to manipulate, the products of periodate oxidation are oftentimes further oxidized, with hypohalite, to carboxylic acids, or are reduced to the corresponding alcohols. Oxidation has been more usually employed than reduction, since acids frequently form crystalline salts and other conveniently prepared derivatives. A process of oxidation of these aldehydic products by hypo-bromite, in the presence of barium carbonate or strontium carbonate, was developed and used extensively by Hudson and his coworkers.107 110 194-199,90s Their method can best be illustrated by an example the further oxidation of the dialdehyde, VI, shown previously (see p. 16) to be obtained by the oxidation of the methyl a-D-aldohexopyranosides. The isolation of... 

It may be noted that, since the distribution coefficient is smaller than unity, the solid phase becomes depleted in strontium relative to the concentration in the aqueous solution. The small value of D may be interpreted in terms of a high activity coefficient of strontium in the solid phase, /srco3 38. If the strontium were in equilibrium with strontianite, [Sr2+] 10 3-2 M, that is, its concentration would be more than six times larger than at saturation with Cao.996Sro.oo4C03(s). This is an illustration of the consequence of solid solution formation where with Xcaco3 /caC03 -1 ... 

The fuel cell analyzed in the present section is a disk-shaped anode-supported SOFC, currently produced by H.C. Starck/InDEC B.V As illustrated in Figure 4.1 [1], the anode material is a cermet of nickel oxide doped with yttrium stablilized zir-conia (NiO/8YSZ). The cathode is composed of two layers one made of 8YSZ with strontium-doped LaMnC>3 (8YSZ/LSM) and one of LSM. The electrolyte consists of a dense 8YSZ material. 

Purposely added elements also often help to pinpoint an exact locus of failure as illustrated in Figure 11. Here a failure is shown to have occurred near the priner-aluminum alloy interface as indicated by SIMS and other spectra which showed elements of the corrosion inhibitor (strontium chromate) on the failure surfaces. Similar work using SIMS has been used to infer environmental corrosion resistance and to determine thickness of thin silanized surfaces... 

Sorption on oxides and hydrous oxides has been extensively studied both experimentally and theoretically. In order to define an ideal oxide or hydrous oxide exchanger, we will rely on experiments with well-defined sorbents such as chromatographic alumina (1-4). Briefly, the adsorption characteristics of oxides and hydrous oxides are (1) At high pH, they act as cation exchangers but with less sensitivity to the total salt concentration than clay minerals. This behavior is illustrated in Figure 2, where sorption of strontium on alumina is shown. 

Figure 7.39. Schematic diagram illustrating the effects of climate on meteoric diagenetic pathways for coeval carbonates originally composed of a polymineralic assemblage of calcite with various amounts of magnesium and strontium-rich aragonite. (After James and Choquette, 1984.)...

The method consists in first converting the sulphate into the carbonate by boiling it with a concentrated solution of sodium carbonate, and then dissolving the carbonate in hydrochloric acid, thereby yielding a solution of the chloride. The conversion of solid strontium sulphate into solid strontium carbonate furnishes an interesting illustration of the solubility product principle, for the solubility of these two salts in pure water is as follows ... 

Bonding in the silica-type covalent phosphate structure is illustrated in Fig. 8.5. Because this bonding is covalent, the resulting minerals are very hard and their aqueous solubility is extremely low. These properties make them attractive for the disposal of radioactive barium and strontium isotopes formed during nuclear reactions. These two isotopes may be converted to their covalent phosphate structures as Sr3(P04)2 and Ba3(P04)2 and can be disposed or stored in repositories safely. 

We turn now to a very important class of materials that have the formula /IBC3, with the C frequently oxygen. Strontium titanate is a familiar example and one we shall use for illustrative purposes. Titanium is in the D4 column of the Solid State Table, having four electrons beyond its argonlike core. Strontium has two electrons outside its kryptonlike core, so we may think of the six valence electrons as having been transferred to the three oxygen atoms to form a simple ionic system. As we shall see, however, the titanium d states form the lowest conduction band and are important in the bonding properties as well. 

The techniques illustrated in Figures 17 and 18 can be used to establish an approximate compatibility sequence of trace elements for mantle-derived melts. In general, this sequence corresponds to the sequence of decreasing (normalized) abundances in the continental crust shown in Figure 2, but this does not apply to niobium, tantalum, and lead for which the results discussed in the previous section demand rather different positions (see also Hofmann, 1988). Here I adopt a sequence similar to that used by Hofmann (1997), but with slightly modified positions for lead and strontium. 

The distribution of lithophile trace elements (REE + mbidium, caesium, strontium, barium, yttrium, zirconium, hafnium, niobium, tantalum, thorium, and uranium) normalized to primitive mantle (PM) values are illustrated in Figure 16 for a range of peridotite lithologies from the Ronda orogenic Iherzolite massif, and in Figure 17 for ophiolitic and abyssal refractory peridotites. 

Figure 32 Strontium isotope and abundance systema-tics of pure and altered/metasomatized garnet and diopside separates from the Bultfontein kimberlite (after Richardson et al., 1985). Shaded region indicates the area defined by phlogopite addition. Tick marks on mixing lines illustrate % of component added.

Since the Precambrian, the Sr/ Sr of seawater has fluctuated between —0.7070 and —0.7092 as the result of variations in the relative rates of input of Sr-enriched strontium from continental weathering and Sr-depleted strontium from mantle sources. Fluids in sedimentary basins containing Paleozoic strata typically have Sr/ Sr ratios in excess of seawater values that are contemporaneous or coeval with the deposi-tional age of the current host sediment. This is well illustrated by the data of Connolly et al. (1990) for the Alberta Basin, Canada. The enrichment is due to the release of strontium attending the alteration of silicates. Due to the significant increase of Sr/ Sr in seawater since the Jurassic, some formation waters in Cenozoic sedimentary basins actually have Sr/ Sr ratios lower than those of contemporaneous seawater due to the addition of strontium dissolved from older and deeper sedimentary sources... 

FIGURE 10.48 Results of a study illustrating the nature of the calcium requirement by enzymes of the clotting cascade. Factor X, factor n, phospholipid, and the indicated cation were mixed together in a test tube. A small, synthetic substrate was also added. Cations (half-black circle) no addition, ( ) calcium, (O) strontium, (A) barium, ( ) magnesium, (A) magnesium + barium. (Redrawn with permission from Nelsestuen et al, 1976.)... 

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