Strontium and its Compounds

Strontium only important in special applications. Applications spectrum in USA in 1993  

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Strontium and its compounds are mostly derived from celestite, SrS04. The mineral is converted to its carbonate by heating with sodium carbonate. Alternatively, the mineral may be reduced to sulfide by heating with coke. The carbonate or the sulfide is then converted to other strontium salts. 

Strontium and its compounds have relatively few commercial uses. The pure metal is sometimes combined with other metals to form alloys. An alloy is made by melting and mixing two or more metals. The mixture has different properties than the individual metals. Compounds of strontium are sometimes used to color glass and ceramics. They give a beautiful red color to these materials. Strontium compounds also provide the brilliant red color of certain kinds of fireworks. 

An MRL of 2.0 mg/kg/day has been derived for intermediate-duration oral exposure (15-364 days) to stable strontium and its compounds. 

Human exposure to strontium and its compounds occurs primarily by inhalation and ingestion, since absorption is poor following dermal contact. Current suggestions for reducing absorption of radiostrontium include ingestion of antacids containing aluminum phosphate (Ellenhom et al. 1997 ... 

The highest exposures occur occupationally. The National Occupational Hazard Survey conducted by the National Institute for Occupational Safety and Health from 1972 through 1974 concluded that some 2.5 million workers could be exposed to chromium and its compounds in the workplace. The National Occupational Exposure Survey conducted a decade later from 1981 through 1983 estimated a total of almost 200 000 workers were exposed to hexavalent chromium compounds (barium chromate, calcium chromate, chromium trioxide, lead chromate, strontium chromate, and zinc chromate). Occupational exposure occurs primarily from stainless steel production and welding, chromate production, chrome plating, ferrochrome alloys, chrome pigment and tanning industries. 

All other expected relationships of elements or ions may be used in assessing the extent of purification of inorganic substances. Common associations include sodium and potassium calcium, strontium, and barium phosphorus and arsenic arsenic and antimony and iron, cobalt, and nickel. There are a number of less well known but useful associations that are often described in textbooks of geochemistry, including silver with lead and its compounds arsenic with copper and its compounds and manganese in magnesium compounds. 

Bertrand Pelletier (Bayonne, 30 July 1761-Paris, 21 July 1797 (after inhaling chlorine)) was first an assistant to D Arcet, then an apothecary, finally from 1795 professor in the ficole Polytechnique, and a member of government commissions. He worked on arsenic acid, which he obtained by heating arsenious oxide with ammonium nitrate, the crystallisation of deliquescent salts, chlorine, discovering chlorine hydrate independently of Berthollet (see p. 504), ethers, plumbago and molybdenite, and the preparation of phosphorus and its compounds, including phosphorous acid, phosphoric acid, and hydrogen phosphide (discovered by Gei embre) he was severely burned by an accident with phosphorus, which he showed would bum in air under water. He also published on strontium compounds, the analyses of... 

Health and Safety Factors. The strontium ion has a low order of toxicity, and strontium compounds are remarkably free of toxic hazards. Chemically, strontium is similar to calcium, and strontium salts, like calcium salts, are not easily absorbed by the intestinal tract. Strontium carbonate has no commonly recognized hazardous properties. Strontium nitrate is regulated as an oxidizer that promotes rapid burning of combustible materials, and it should not be stored in areas of potential fire hazards. 

Barium [7440-39-3] Ba, is a member of Group 2 (IIA) of the periodic table where it Hes between strontium and radium. Along with calcium and strontium, barium is classed as an alkaline earth metal, and is the densest of the three. Barium metal does not occur free in nature however, its compounds occur in small but widely distributed amounts in the earth s cmst, especially in igneous rocks, sandstone, and shale. The principal barium minerals are barytes [13462-86-7] (barium sulfate) and witherite [14941-39-0] (barium carbonate) which is also known as heavy spar. The latter mineral can be readily decomposed via calcination to form barium oxide [1304-28-5] BaO, which is the ore used commercially for the preparation of barium metal. 

The material is impact-sensitive when dry and is supplied and stored damp with ethanol. It is used as a saturated solution and it is important to prevent total evaporation, or the slow growth of large crystals which may become dried and shock-sensitive. Lead drains must not be used, to avoid formation of the detonator, lead azide. Exposure to acid conditions may generate explosive hydrazoic acid [1], It has been stated that barium azide is relatively insensitive to impact but highly sensitive to friction [2], Strontium, and particularly calcium azides show much more marked explosive properties than barium azide. The explosive properties appear to be closely associated with the method of formation of the azide [3], Factors which affect the sensitivity of the azide include surface area, solvent used and ageing. Presence of barium metal, sodium or iron ions as impurities increases the sensitivity [4], Though not an endothermic compound (AH°f —22.17 kJ/mol, 0.1 kj/g), it may thermally decompose to barium nitride, rather than to the elements, when a considerable exotherm is produced (98.74 kJ/mol, 0.45 kJ/g of azide) [5]. 

Strontium metal is not found in its elemental state in nature. Its salts and oxide compounds constitute only 0.025% of the Earths crust. Strontium is found in Mexico and Spain in the mineral ores of strontianite (SrCO ) and celestite (SrSO ). As these ores are treated with hydrochloric acid (HCl), they produce strontium chloride (SrCy that is then used, along with potassium chloride (KCl), to form a eutectic mixture to reduce the melting point of the SrCl, as a molten electrolyte in a graphite dish-shaped electrolysis apparatus. This process produces Sr cations collected at the cathode, where they acquire electrons to form strontium metal. At the same time, Cl anions give up electrons at the anode and are released as chlorine gas Cl T. 

As a powder, strontium metal may spontaneously burst into flames. Both its metal and some of its compounds will explode when heated. Some of the compounds will explode if struck with a hammer. 

Uranium mineral first is digested with hot nitric acid. AH uranium and radium compounds dissolve in the acid. The solution is filtered to separate insoluble residues. The acid extract is then treated with sulfate ions to separate radium sulfate, which is co-precipitated with the sulfates of barium, strontium, calcium, and lead. The precipitate is boiled in an aqueous solution of sodium chloride or sodium hydroxide to form water-soluble salts. The solution is filtered and the residue containing radium is washed with boiling water. This residue also contains sulfates of other alkahne earth metals. The sohd sulfate mixture of radium and other alkahne earth metals is fused with sodium carbonate to convert these metals into carbonates. Treatment with hydrochloric acid converts radium and other carbonates into chlorides, all of which are water-soluble. Radium is separated from this solution as its chloride salt by fractional crystallization. Much of the barium, chemically similar to radium, is removed at this stage. Final separation is carried out by treating radium chloride with hydrobromic acid and isolating the bromide by fractional crystallization. 

Strontium and all its compounds impart crimson red color in the flame test. The metal in trace concentrations can be analyzed by various instrumental methods that include flame-and fumace-AA, ICP-AES, ICP/MS, x-ray fluorescence, and neutron activation analysis. 

It has been observed in CVD as well as in ALD depositions that coordi-natively unsaturated y0-diketonate-type compounds may oligomerise or react with the environment and become less volatile [15,16,66,67]. This is a cause of instability, especially with larger and basic central ions such as strontium and barium. y0-diketonate-type chelates can be protected against oligomerisation and roomOtemperature reactions with moisture by adducting them with neutral molecules (Fig. 4) [68-71]. 

The most important chemical parameter affecting the deposition and subsequent mobility of radioactive aerosols, such as the nuclides 90Sr and 137Cs examined in this study, is their solubility in rainwater. If these aerosols are dissolved in precipitation, the main factor in their transport is the movement of the rainwater, not the transport of insoluble aerosol particles. Huff and Kruger (2) examined the solubility products of strontium and chemically similar compounds which may carry trace amounts of 90Sr, and they estimated that strontium should be soluble in precipitation. Solubility tables also indicate that cesium compounds likely to exist in precipitation should be soluble. It was noted that the possibility did exist that some of the fission product "Sr and 137Cs might be bound within the structure of insoluble natural aerosols or nuclear weapon debris. 

Why is it important to remove compounds of calcium, strontium and magnesium before brine is electrolysed ... 

In the early 1990s, there existed several classes of extractants for actinides (CMPO), for cesium and more generally alkali cations, and for strontium and alkaline earth cations (crown ethers and cosan). The combination of these extractants and the grafting of these functions on calixarene platforms have led to new classes of extremely efficient and selective extractants, in particular calixarene-crown, which are presently applied in the United States to treat the huge amounts of waste at the SRS. Calixarenes/ CMPO, crown ethers/cosan, CMPO/cosan, and more recently calixarenes/CMPO/ cosan are promising compounds. It is desirable that these studies, conducted at the international level, continue in particular to obtain a better understanding of the complex mechanisms of extraction of these compounds.127187... 

CCD and its brominated analog (Br-COSAN) are very widely studied as potential components of extraction mixtures for radionuclide separation. These compounds were proposed for extraction more than 30 years ago,17 and already in the first publications, polyethylene glycols (PEGs) were used for simultaneous extraction of cesium and strontium. An excellent review of extraction by carborane compounds was recently published 18 so, in this paper, mainly works published after 2003 and not included in the previous review will be discussed. 

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