Strontium fluoride

Strontium fluoride [7783-48-4] SrF2, forms colorless cubic crystals or a white powder with a specific gravity of 4.24 and a melting point of 1190°C. 

Aqueous hydrofluoric acid can be freed from lead by adding ImL of 10% strontium chloride per KXhnL of acid, lead being co-precipitated as lead fluoride with the strontium fluoride. If the hydrofluoric acid is decanted from the precipitate and the process repeated, the final lead content in the acid is less than 0.003 ppm. Similarly, lead can be precipitated from a nearly saturated sodium carbonate solution by adding 10% strontium chloride dropwise (l-2mL per lOOmL) followed by filtration. (If the sodium carbonate is required as a solid, the solution can be evaporated to dryness in a platinum dish.) Removal of lead from potassium chloride uses precipitation as lead sulfide by bubbling H2S, followed, after filtration, by evaporation and recrystallisation of the potassium chloride. 

Goldschmidt predicted from his empirical rule that calcium chloride would not have the fluorite structure, and he states that on investigation he has actually found it not to crystallize in the cubic system. Our theoretical deduction of the transition radius ratio allows us to predict that of the halides of magnesium, calcium, strontium and barium only calcium fluoride, strontium fluoride and chloride, and barium fluoride, chloride,... 

The favored defect type in strontium fluoride, which adopts the fluorite structure, are Frenkel defects on the anion sublattice. The enthalpy of formation of an anion Frenkel defect is estimated to be 167.88 kJ mol-1. Calculate the number of F- interstitials and vacancies due to anion Frenkel defects per cubic meter in SrF2 at 1000°C. The unit cell is cubic, with a cell edge of 0.57996 nm and contains four formula units of SrF2. It is reasonable to assume that the number of suitable interstitial sites is half that of the number of anion sites. 

Strontium compounds, 23 319-324 estimated distribution of, 23 3201 world production of, 23 319-320 Strontium cyanide, 8 197 Strontium ferrate (1 1), 5 598 Strontium fluoride, 23 323 Strontium fluoroborate tetrahydrate, 4 153 Strontium halides, 23 323 Strontium hexaferrite, 23 323 Strontium hydride, 13 613 Strontium hydroxide, 23 324 Strontium iodide, 23 323 Strontium-lead alloys, 14 779 Strontium minerals, 23 320 producers of, 23 319 Strontium nitrate, 23 319, 321, 323 Strontium oxide, 23 318, 324 Strontium peroxide, 18 396, 23 324 Strontium-silicon alloy, 22 520 Strontium sulfate, 23 322, 324 Strontium sulfide, 23 322 Strontium titanate... 

Some compounds, such as strontium chromate and strontium fluoride, are carcinogens and toxic if ingested. Strontium-90 is particularly dangerous because it is a radioactive bone-seeker that replaces the calcium in bone tissue. Radiation poisoning and death may occur in people exposed to excessive doses of Sr-90. Strontium-90, as well as some other radioisotopes that are produced by explosions of nuclear weapons and then transported atmospherically, may be inhaled by plants and animals many miles from the source of the detonation. This and other factors led to the ban on atmospheric testing of nuclear and thermonuclear weapons. 

Now there must be twice as many fluoride ions as strontium iocs, so the coordination number of the strontium ion must be twice as large as that of fluoride. Coordination numbers of 8 (Sr2 +) and 4 (F ) are compatible with the maximum allowable coordination numbers and with the stoichiometry of the crystal. Strontium fluoride crystallizes in the fluorite lattice (Fig. 4.3). 

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