Applications
The first large scale application of strontium was in the production of sugar from sugar beet. Although a crystallisation process using strontium hydroxide was patented by Augustin-Pierre Dubrunfaut in 1849 the large scale introduction came with the improvement of the process in the early 1870s. The German sugar industry used the process well into the 19th century. Prior to World War I the beet sugar industry used 100,000 to 150,000 tons of strontium hydroxide for this process per year.
Strontium carbonate or other strontium salts are used in the manufacture of fireworks, as they impart a deep red color to the firework.
Strontium metal is used in strontium 90%-aluminium 10% alloys of an eutectic composition for the modification of aluminium-silicon casting alloys. AJ62, a durable, creep-resistant magnesium alloy used in car and motorcycle engines by BMW, contains 2% strontium by weight.
Strontium is used in scientific studies of neurotransmitter release in neurons. Like calcium, strontium facilitates synaptic vesicle fusion with the synaptic membrane. But, unlike calcium, strontium causes asynchronous vesicle fusion. Therefore, replacing calcium in a culture medium with strontium allows scientists to measure the effects of a single-vesicle fusion event, e.g., the size of the postsynaptic response elicited by the neurotransmitter content of a single vesicle.
The important concept for isotopic tracing is that Sr derived from any mineral through weathering reactions will have the same 87Sr/86Sr as the mineral. Therefore, differences in 87Sr/86Sr among ground waters require either (a) differences in mineralogy along contrasting flowpaths or (b) differences in the relative amounts of Sr weathered from the same suite of minerals. This latter situation can arise in several ways. First, differences in initial water chemistry within a homogeneous rock unit will affect the relative weathering rates of the minerals. For example, sections of the soil zone affected by evaporative concentration of recharge waters or by differences in pCO2 can be expected to have different 87Sr/86Sr. Secondly, differences in the relative mobilities of water at scales ranging from inter-grain pores to the catchment scale may also profoundly affect 87Sr/86Sr (Bullen et al., 1996). For example, the chemical composition and the resultant 87Sr/86Sr in immobile waters at a plagioclase-hornblende grain boundary versus a quartz-mica boundary will be different. Third, a difference in the relative "effective" surface areas of minerals in one portion of the rock unit will also cause differences in chemistry and isotopic composition; "poisoning" of reactive surfaces by organic coatings is an example of this kind of process. In a fundamental sense, because the waters in shallow systems are not in chemical equilibrium with the rocks, it is unrealistic to expect that waters along flowpaths within even a constant-mineralogy unit should have a constant 87Sr/86Sr. Instead, the waters moving along specific flowpaths slowly react with the rocks and gradually approach chemical equilibrium over long time-periods.
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