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Degrees of german carbonate hardness (°dKH or °KH; the dKH is from the German deutsche Karbonathärte) is a unit of water hardness, specifically for temporary or carbonate hardness. Carbonate hardness is a measure of the concentration of carbonates such as calcium carbonate (CaCO 3) and magnesium carbonate (MgCO 3) per volume of water. As a ...
Recommendations have been made for the minimum and maximum levels of calcium (40–80 ppm) and magnesium (20–30 ppm) in drinking water, and a total hardness expressed as the sum of the calcium and magnesium concentrations of 2–4 mmol/L. [14] Other studies have shown weak correlations between cardiovascular health and water hardness.
Vickers hardness test; Brinell scale This page was last edited on 16 November 2024, at 12:16 (UTC). Text is available under the Creative Commons ...
Carbonate hardness, is a measure of the water hardness caused by the presence of carbonate (CO 2− 3) and bicarbonate (HCO − 3) anions. Carbonate hardness is usually expressed either in degrees KH (from the German "Karbonathärte"), or in parts per million calcium carbonate ( ppm CaCO 3 or grams CaCO 3 per litre|mg/L).
There are several scales of durometer, used for materials with different properties. The two most common scales, using slightly different measurement systems, are the ASTM D2240 type A and type D scales. The A scale is for softer ones, while the D scale is for harder ones. The image of Bareiss digital durometer is shown in the photo.
A variety of hardness-testing methods are available, including the Vickers, Brinell, Rockwell, Meyer and Leeb tests. Although it is impossible in many cases to give an exact conversion, it is possible to give an approximate material-specific comparison table for steels .