Strontium occurrence

Occurrence. The principal strontium mineral is celestite, naturally occurring strontium sulfate. Celestite and celestine [7759-02-6] both describe this mineral. However, celestite is the form most widely used in Knglish-speaking countries. Celestite has a theoretical strontium oxide content of 56.4 wt %, a hardness of 3—3.5 on Mohs scale, and a specific gravity of 3.96. It is usually white or bluish white and has an orthorhombic crystal form. 

Stronlianile, 385 Strontium atomic size, 379 chemistry, 382 electron configuration. 378 heal of vaporization, 305 hydroxide, K,p, 383 ionization energies, 379 occurrence, 385 properties, 381 Structural formula, 31 Structural isomers, 327 Styrene, 345 Sublimation, 176 Substance, 28 pure, 29, 65, 70... 

Among condensed phosphate systems with polyvalent cations, the very complicated calcium salts have been much studied and a great number of compounds have been detected, often with several modifications (5, 27, 28, 34, 54, 79, 186, 137, 191, 198, 204, 211, 276, 805, 830). In this system special interest attaches to the occurrence of crystalline cross-linked phosphates (see Section V) and of calcium pentaphosphate, CayiPsOis (see Section IV,D,/). The end-product obtained by heating Ca(H2P04)2 in the free atmosphere is the high-molecular calcium polyphosphate, which crystallizes in several forms. The condensed strontium phosphates (246, 805) are similarly complicated and cannot readily be made the subject of a brief review. 

Finally, we note that the photocorrosion process is strongly pH-dependent, occurring most readily in strongly acid solutions, and that the presence of a carboxylic acid is required for the occurrence of severe photocorrosion. In Table II we present analytical results, based on inductively coupled argon plasma (ICP) emission spectroscopy, for representative electrolyte solutions after 6-8 hr. of photo-Kolbe electrolysis with n-SrTiC anodes. It can be seen that the formation of soluble strontium and titanium species is... 

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

In addition to HIE, the melts are probably enriched in volatiles, notably in water. Uranium, strontium, and lead may indeed be selectively enriched in water-rich melts/fluids (Gill, 1990 Keppler and Wyllie, 1990 Erenan et al., 1996 Keppler, 1995 You et al., 1996). This might account for the frequent occurrence of positive anomalies of strontium (and lead—not shown) on PM-normalized diagrams, and for the U/Th ratios systematically higher than PM values, both in whole rocks (Figures 16 and 17) and in acid-leached minerals (Figure 21). 

Judd and Pope [36] conclude that because the activation energies for decompositions of CaCOj, SrCO, and BaCOj are all close to the corresponding enthalpies of dissociation (apparent values of , are 180,222 and 283 kJ mol and A//, 178, 235 and 269 kJ mol, respectively) the mechanisms of decomposition in all three substances are the same as that proposed by Hills [18] for calcite. Strontium carbonate [37] generally resembles the calcium salt in that an increase in sample size results in a decrease in reaction rate. Differences in behaviour were ascribed [37] to the occurrence of a crystallographic transformation and to fusion. 

The occurrence of isotopes among the 83 most abun-dantelements is widespread, but separation methods are complicated and costly. Twenty-one elements have no isotopes, each consisting of only one kind of atom (see note below). The remaining 62 natural elements have from 2 to 10 isotopes each. There are 287 different isotopic species in nature noteworthy among them are oxygen-17, carbon-14, uranium-235, cobalt-60, and strontium-90, all but the first being radioactive. 

For those interested in mineral matter in coal, an awareness that some partings may be of volcanic origin may be useful in explaining the distribution of some of these layers and the occurrences of some unusual components, such as strontium, phosphate, or uranium. Volcanic ash partings are likely to be more widespread and uniform in texture, composition and thickness than the more common partings of fluvial origin. They are also more likely to show marked differences from layer to layer, and to contain exotic mineral or chemical components. 

Sporadic occurrences of minor amounts of early siderite formed at low temperature (20-40 °C), frequently in association with detrital biotites. The fluid from which siderite precipitated had a consistent oxygen, carbon and strontium isotopic composition over great distances, which is best explained as representing homogeneous mixing of Jurassic seawater and meteoric water at field scale. Carbon was predominantly supplied by organic sources. 

The amount and quality of information in these studies varies greatly and only a few of the more recent papers applied a combination of several different methods to decipher the origin of saddle dolomite. We scanned published work for the following information on saddle dolomite occurrences optical mineralogy, cathodoluminescence (CL) characteristics, elemental composition, carbon, oxygen and strontium isotopic compositions, and fluid inclusion analysis. In the following sections we shall address these types of data in detail. 

Physical and Chemical Properties of Strontium and Strontium Compounds 4-3. Percent Natural Occurrence and Radioactive Properties of Isotopes of Strontium... 

The physical properties of strontium metal and selected strontium compounds are listed in Table 4-2. The percent occurrence of strontium isotopes and radiologic properties of strontium isotopes is listed in Table 4-3. 

Exposure Levels in Humans. The primary source of recent information on the occurrence of 90Sr in drinking water is the National Inorganics and Radionuclides Survey conducted by EPA. Better and more recent information on background levels in the environment (e.g., air, food, water, and soil) may be useful. Additional information on bioavailability of strontium and radiostrontium from environmental media is necessary. 

USGS. 1963. Occurrence and distribution of strontium in natural water Chemistry of strontium in natural water Geological survey water-supply paper 1496-D. Washington, DC U.S. Atomic Energy Commission. U.S. Geological Survey. 

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 amounts of strontium found in the flora correlate positively and species-specifi-cally with species-specific amounts of Ca (Table 6.21). Although both elements were apparently taken up in a similar ratio, Ca-rich species or parts of plants were found also to contain high levels of Sr, whereas Ca-poor species proved to be Sr-poor. The almost constant Ca Sr ratio may reduce the occurrence of Sr exposure, and may also be the cause of considerable changes in the proportions of both elements in the skeletons of animals and humans. The cells of plants are unable to distinguish between calcium and strontium (Anke et al. 1999). 

A more common type of spectral interference in either emission or absorption measurements arises from the occurrence of band emission-spectra due to molecular species in the flame. (In fact, many elements can be measured by means of the band spectra of the molecules they form in certain flames.) Calcium and strontium, for example, exist partially as molecular hydroxides and oxides in a flame and emit bands in the vicinity of both the sodium and lithium resonance lines. When the alkaline-earth/alkali-metal ratio is high, the interference can become serious, unless a high-resolution monochromator is used. 

In 1790, A. Crawford and W. Cruickshank reported the occurrence of a new earth , which in 1808 Sir Humphrey Davy isolated in an impure form by means of electrolysis. The metal was named strontium (Sr), after Strontian, a town in Argyllshire, Scotland, where it was first found [1]. In 1870, interest in the physiological similarity of strontium to calcium began when Papillon and Konig reported that this element could replace calcium in bone. In 1883, Ringer and Sainsbury... 

---