| 单词 | permanent hardness |
| 释义 | > as lemmaspermanent hardness permanent hardness n. hardness of water that cannot be removed by boiling. ΘΚΠ the world > matter > liquid > water > [noun] > hardness or softness of hardness1712 softness1712 permanent hardness1870 temporary hardness1895 1870 H. E. Roscoe Lessons in Elem. Chem. 170 Calcium sulphate..is a very common impurity in spring water, giving rise to what is termed permanent hardness, as it cannot be removed by boiling. 1969 H. T. Evans tr. G. Hägg Gen. & Inorg. Chem. xxvi. 666 Carbonate precipitation on boiling causes the water to lose its carbonate hardness or temporary hardness while a permanent hardness remains. < as lemmas |
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