Strontium Carbonate (or Strontianite) is a type of a whitish grey coloured powder which is the carbonate salt of Sodium, having the formula SrCO3. It occurs naturally as the mineral Strontianite. It is colourless, odourless, and is a weak base due to it being a Carbonate and thus reacts with acids. In addition, it is insoluble in water and is stable. It is used in various industries out of which its application in the Pyrotechnics industry is the most common.
It is synthetically manufactured using two techniques: Black Ash method and Soda Ash method. The yield of Strontium Carbonate in the Black Ash process is a minimum of 98% while for the Soda Ash process it is 97%.
Black Ash Process
Crushed and screened Celestite is mixed with powdered Charcoal and heated till 1100 degrees Celsius to form Strontium Sulfide due to expulsion of Oxygen as Carbon Dioxide. This compound is water soluble. Strontium Sulfide is then dissolved in water and combined with some Carbon Dioxide (by by bubbling it through the solution) or Soda Ash, such that Strontium Carbonate precipitates out. This is then filtered, dried, ground, and packaged. The by product from this process is Sulphur which can be reused. This technique is more commonly used nowadays.
Soda Ash Process
Ground Celestite is washed and separated from water. This slurry is then combined with Soda Ash and treated with steam for 1 to 3 hours to give Strontium Carbonate and Sodium Sulphate. Using Centrifuging technique, this Strontium Carbonate, being water soluble, is separated from the mixture, dried, ground, and packaged.
Due to its ability to be not hygroscopic, neutralize acid, and its low cost, it is widely used as a red colourant for firecrackers. It is also used in road flares.
It is used for making CTV to allow absorption of electrons due to the presence of cathode.
It is widely used as a glazing agent. It helps modify the colour of many metal oxides and act as a flux too.
It is used for making luminous paints, iridescent glass, Strontium Oxide/salts for sugar refining, Strontium Ferrites (permanent magnets used in doors and loudspeakers) etc.