According to the provided reference, temporary hardness is related to the concentration of specific dissolved mineral substances in water, primarily magnesium bicarbonate [Mg(HCO₃)₂] and calcium bicarbonate [Ca(HCO₃)₂]. The reference presents examples showing how temporary hardness values are associated with the concentrations of these compounds.
Components of Temporary Hardness
Temporary hardness is caused by bicarbonates of multivalent cations, predominantly calcium (Ca²⁺) and magnesium (Mg²⁺). The reference specifically identifies these compounds in a sample:
- Magnesium Bicarbonate [Mg(HCO₃)₂]
- Calcium Bicarbonate [Ca(HCO₃)₂]
These substances contribute to temporary hardness because they precipitate out of solution as carbonates (CaCO₃, MgCO₃) when the water is boiled, effectively reducing the hardness.
Reference Examples for Calculating Temporary Hardness
The provided reference includes examples illustrating temporary hardness:
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Direct Assignment: In one instance, the temporary hardness value is presented as being directly equal to the concentration of magnesium bicarbonate:
Temporary hardness = Mg(HCO₃)₂ = 11.50 mgs/Lit.
This suggests that, in some specific contexts or problems, the temporary hardness value might be given or considered equivalent to the concentration of a primary temporary hardness-causing substance like Mg(HCO₃)₂. -
Listing Components: Another example in the reference provides analytical data for a water sample, listing the concentrations of various dissolved substances, including the key components of temporary hardness:
A sample of water contained the following data in milligrams per litre:- Mg(HCO₃)₂ = 14.6
- MgCl₂ = 9.5
- MgSO₄ = 6.0
- Ca(HCO₃)₂ = 16.2
While this example lists the concentrations of both Mg(HCO₃)₂ and Ca(HCO₃)₂, which are the substances contributing to temporary hardness, the reference does not explicitly show the calculation method for combining these values to determine the total temporary hardness in this specific case. Standard methods typically involve converting the concentrations of these substances to an equivalent concentration of calcium carbonate (CaCO₃) and summing them, but this conversion process is not detailed in the provided reference.
Based on the reference, understanding temporary hardness calculation involves identifying the concentrations of magnesium bicarbonate and calcium bicarbonate present in the water sample, as these are the compounds that cause this type of hardness.
