Total Hardness, Model HA-71A Digital Titrator Other test kits are available for measuring calcium and magnesium hardness separately. Test kit models 5-B, 5-EP, and 5-EP/MG-L, which use UniVer ® reagent, work best for industrial samples that may have high concentrations of metals, such as copper. Total hardness test kit model HA-71A, uses ManVer ® indicator and works best for natural water samples, especially when iron or manganese is present, or when alkalinity is high. This hardness test uses a dropper to add the EDTA solution to the sample and the drop counts are proportional to the water hardness. You can also measure calcium hardness separately from magnesium hardness by adjusting the pH and using different indicators. You can titrate a sample for total hardness using a burette or use a water hardness test kit. A titration involves adding indicator and then titrant solution in small increments to a water sample until the sample changes color. Hardness is commonly measured by colorimetric titration with an EDTA solution.
Water quality measuring instruments software#
Visit these related parameter pages to learn more about ammonia and nitrogen.Īt Hach ®, find the testing equipment, resources, training, and software you need to correctly monitor and manage water hardness in your specific application. To optimize these processes, it is sometimes important to monitor calcium and magnesium levels separately, along with total hardness.Īdditionally, magnesium can interfere with other water quality tests such as nitrogen, ammonia-salicylate methods. Therefore, water softening by either precipitation or ion exchange is often necessary to remove hardness. While some hardness may be acceptable in certain water quality applications, others require zero hardness to prevent scaling and damage to equipment. In general, hard water forms solid deposits comprised of mainly calcium and magnesium salts and can damage equipment, while soft water may be corrosive and therefore, it is important measuring and knowing levels of hardness in your process water to maintain the delicate balance between scaling and corrosivity. Total hardness is the sum of all carbonate and non-carbonate salts of calcium and magnesium present in the water. Because alkalinity is also reported as CaCO 3, the results of the two tests can be compared directly. In the US, hardness is typically reported in mg/L as CaCO 3 or gpg (grain per gallon) as CaCO 3. Any excess hardness is non-carbonate hardness. If the alkalinity is equal to or greater than the hardness, all of the hardness is carbonate. non-carbonate hardness can be found by measuring alkalinity. The Relationship Between Alkalinity and Water Hardness Non-carbonate hardness is sometimes referred to as permanent hardness.
Non-carbonate hardness is caused primarily by calcium and magnesium nitrates, chlorides and sulfates. This is the primary cause of scale formation in water heaters and boilers. When such bicarbonates are heated, they precipitate in solid carbonate forms. Sometimes it is referred to as temporary hardness because it can be removed or lowered by boiling. Carbonate hardness refers to calcium and magnesium bicarbonate. Hardness can be classified as carbonate and non-carbonate hardness. Therefore, hardness is generally considered to be the concentration of calcium and magnesium ions in water. The concentration of calcium and magnesium in natural waters generally far exceeds that of any other polyvalent cation. The minerals that precipitate with soap are represented by cations of polyvalent metals such as calcium, magnesium, iron, manganese and zinc. Water Hardness is Generally the Concentration of Calcium and Magnesium Ions in Water When the minerals are no longer available, the soap forms a lather and works as a cleaning agent. As more soap is added, solids continue to form until the minerals are depleted. This decreases the cleaning efficiency of the soap and forms soap scum. When soap is mixed with hard water, the minerals combine with the soap and form a solid precipitate.
The term comes from an expression of how difficult or "hard" it is to wash clothes with the water. Hardness is a measure of the soap consuming capacity of water.
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