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HARDNESS IT IS A CHARACTERISTIC DUE TO THE QUANTITY OF DISSOLVED CALCIUM AND MAGNESIUM SALTS, CALCIUM AND MAGNESIUM BICARBONATES ARE SOLUBLE, CARBONATES AREN'T. WARMED UP SOLUTIONS OF CALCIUM AND MAGNESIUM BICARBONATE TRANSFORM INTO INSOLUBLE CARBONATE, WATER AND CARBON DIOXIDE.
A shell, a piece of marble or a limestone can be dissolved in chloridric acid (the necessary amount: if the acid is in excess, it should be neutalized with sodium hydroxide) , soap must be added to the two solutions and violently shaken. Where the shell had dissolved it won't be any foam. Calcium and magnesium form solid deposits when warmed:
QUANTITATIVE ANALYSIS OF HARDNESS ( complexometryc titration: EDTA ):
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