Amount of calcium and magnesium present in a water sample is determined. The determination of the hardness of water is important in water treatment plants. RXSOL-60-6232-100 is standarised and caliberated solution of colour indicator, which will help for determination of HARDNESS standard by giving the greatest color change as the end point.
Calcium Carbonate Standard Solution making Method :::
Weigh to the nearest 0.1 mg approximately 0.5 g of dry primary standard CaCO3 into a clean, dry 50 mL beaker. Transfer most of the CaCO3 without loss to a dry funnel inserted in the top of a dry 100 mL volumetric flask. Transfer of the last particles is unnecessary. Do not use liquid in this transfer. Weigh the beaker and any remaining calcium carbonate to the nearest 0.1 mg, obtaining the weight of CaCO3 in the flask by difference. Tap the funnel to transfer most of the solid, and then rinse the last particles through the funnel into the flask with a milliliter of 12 M HCl. Add 1 mL more of 12MHCl to each flask by rapid drop wise addition. Warm if necessary to complete the dissolution. When dissolution is complete, remove the funnel, rinsing inside and out with demineralized water from a wash bottle as it is being removed. Fill the flask to the mark with demineralized water, stopper, and mix well.
Preparation of EDTA Solution :::
Prepare an approximately 0.015 M EDTA solution by adding 2.5 g of the disodium salt, 10 mL of 1% MgCl2 solution, and 1.5 mL of 6MNH3 to about 450 mL of water. In this experiment use only distilled water purified by passage through a column containing either a cation-exchange resin or a mixture of cation and anion-exchange resins. ( http://rxmarine.com/DemineralisedWater )