Gesamthärte / Total hardness
Online Tutorial materials in Biology for the education department at the LMU.
Lehrerbildung@LMU
The sum of calcium and magnesium salts is called total hardness.
The name „hardness“ primarily leads back to the effect of calcium ions to lower the cleaning properties of soap by forming difficult or unsolvable lime soap (calcium salts
of higher fatty acids such as palmitic acid). As such hardness components, calcium and magnesium are taken into account together. In natural water bodies, strontium and barium salts can be disregarded due to their very low concentrations (their carbonates and sulfates are hardly soluble). Therefore, the water hardness caused by hydrogen carbonates is often referred to as temporary hardness. The salts of other acids (such as hydrochloric or sulfuric acid) remain in solution even when the water is heated. Such hardness is called permanent hardness or sulfate-hardness.
Depending on the amount of calcium and magnesium salts, water is classified as hard or soft in different gradations:
Very soft: 0–3.8 °e
Soft: 5–8.8 °e
Medium hard 10–13.8 °e
Fairly hard: 15°e–21.3 °e
Hard: 22.5 – 37.5 °e
Very hard: more than 37.5 °e
The newly developed tests are based on our proven VISOCOLOR ® system and were developed as high-quality VISOCOLOR ® SCHOOL test specifically for schools.
Director and creator of the film:
VIKTORIIA KAMSKA
Played by:
Immanuel Görens
Production:
Dr. Martina Bryce and Dr. Jennifer Flechsler
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