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Lime softening (also known as lime buttering, lime-soda treatment, or Clark's process) [1] is a type of water treatment used for water softening, which uses the addition of limewater (calcium hydroxide) to remove hardness (deposits of calcium and magnesium salts) by precipitation.
Water softening is the removal of calcium, magnesium, and certain other metal cations in hard water. The resulting soft water requires less soap for the same cleaning effort, as soap is not wasted bonding with calcium ions.
However, there is an equilibrium between dissolved calcium bicarbonate and dissolved calcium carbonate as represented by the chemical equation Ca 2+ + 2 HCO − 3 ⇌ Ca 2+ + CO 2− 3 + CO 2 + H 2 O. Note that CO 2 is dissolved in the water. Carbon dioxide dissolved in water (aq) tends to equilibrate with carbon dioxide in the gaseous state (g):
In a solution where only CO 2 affects the pH, carbonate hardness can be used to calculate the concentration of dissolved CO 2 in the solution with the formula CO 2 = 3 × KH × 10 (7-pH), where KH is degrees of carbonate hardness and CO 2 is given in ppm by weight. [citation needed]
He became known for the discovery of the phosphate of soda, and the process of lime softening of hard water the 'Clark process'. A Clark degree (°Clark) of water hardness is defined as one grain (64.8 mg) of CaCO 3 per Imperial gallon (4.55 litres) of water, equivalent to 14.254 ppm. and 10^5 parts of water
Calcium oxide (formula: Ca O), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic , alkaline , crystalline solid at room temperature . The broadly used term lime connotes calcium-containing inorganic compounds , in which carbonates , oxides , and hydroxides of calcium, silicon , magnesium ...
Carbonatation is a slow process that occurs in concrete where lime (CaO, or Ca(OH) 2 ) in the cement reacts with carbon dioxide (CO 2) from the air and forms calcium carbonate. The water in the pores of Portland cement concrete is normally alkaline with a pH in the range of 12.5 to 13.5.
Eminently hydraulic lime (NHL 5) is used for external work in exposed areas, such as chimneys and for floor slabs/underpinning. Eminently hydraulic lime contains clay in the range of 21% to 30%. Properties of eminently hydraulic lime are close to those of cement. Eminently hydraulic lime sets within one day after the addition of water.