【Daily Question No. 38】February 7, 2021

Error. Analysis: Differences between permanent hardness and temporary hardness. 1. Difference in meaning: Permanent hardness, also known as non-carbonate hardness, is primarily caused by the non-bicarbonates of calcium and magnesium; there is also a small amount of carbonate hardness involved. Temporary hardness, also known as carbonate hardness, is part of the total hardness of water. That is, the hardness formed by calcium and magnesium ions in water that are bound to bicarbonate ions and a small amount of carbonate ions. 2. Differences in hardness removal: Permanent hardness cannot be removed by heating and decomposition methods. Temporary hardness refers to the hardness that can be removed relatively easily from water, as the bicarbonates of calcium and magnesium decompose when the water is boiled, forming corresponding carbonate precipitates that are removed from the water. 3. Differences in the components: Permanent hardness includes CaSO4, MgSO4, CaCl2, MgCl2, Ca(NO3)2, Mg(NO3)2, etc. Temporary hardness includes: Ca(HCO3), CaCO3, Mg(HCO3)2, Mg(OH)2, etc.