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Salting out (also known as salt-induced precipitation, salt fractionation, anti-solvent crystallization, precipitation crystallization, or drowning out) [1] is a purification technique that utilizes the reduced solubility of certain molecules in a solution of very high ionic strength.
A practical example used very widely in areas drawing drinking water from chalk or limestone aquifers is the addition of sodium carbonate to the raw water to reduce the hardness of the water. In the water treatment process, highly soluble sodium carbonate salt is added to precipitate out sparingly soluble calcium carbonate .
The 3rd analytical group of cations includes ions which form hydroxides that are insoluble even at low concentrations. Cations in the 3rd group are, among others: Fe 2+, Fe 3+, Al 3+, and Cr 3+. The group is determined by making a solution of the salt in water and adding ammonium chloride and ammonium hydroxide. Ammonium chloride is added to ...
The chemical garden relies on most transition metal silicates being insoluble in water and colored. When a metal salt, such as cobalt chloride, is added to a sodium silicate solution, it will start to dissolve. It will then form insoluble cobalt silicate by a double displacement reaction. This cobalt silicate is a semipermeable membrane.
The solubility of a specific solute in a specific solvent is generally expressed as the concentration of a saturated solution of the two. [1] Any of the several ways of expressing concentration of solutions can be used, such as the mass, volume, or amount in moles of the solute for a specific mass, volume, or mole amount of the solvent or of the solution.
Salt is also used to increase the curing of concrete in cemented casings. [10] In textiles and dyeing, salt is used as a brine rinse to separate organic contaminants, [12] to promote "salting out" of dyestuff precipitates, and to blend with concentrated dyes to increase yield in dyebaths and make the colors look sharper. One of its main roles ...
While precipitation reactions can be used for making pigments, removing ions from solution in water treatment, and in classical qualitative inorganic analysis, precipitation is also commonly used to isolate the products of an organic reaction during workup and purification operations. Ideally, the product of the reaction is insoluble in the ...
Exposure of aqueous solutions of strontium chloride to the sodium salt of the desired anion often leads to formation of the solid precipitate: [9] [2] SrCl 2 + Na 2 CrO 4 → SrCrO 4 + 2 NaCl SrCl 2 + Na 2 CO 3 → SrCO 3 + 2 NaCl SrCl 2 + Na 2 SO 4 → SrSO 4 + 2 NaCl. Strontium chloride is often used as a red colouring agent in pyrotechnics.