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实验室中常常要用到少量的硼酸。硼酸是一个一元弱酸,Ka=5.8×10~(-10)。。硼酸微溶于冷水,但在热水中溶解度较大。硼酸同强碱如NaOH中和时,在浓碱溶液中得到偏硼酸盐NaBO_2,在稀碱溶液中得到四硼酸盐(硼砂)Na_2B_4O_5(OH)_4·8H_2O。但是反过来,向任何一种硼酸盐加酸时,总是得到硼酸H_3BO_3,因为硼酸有较低的溶解度而容易从溶液中析出。我们试着利用硼酸的这些性质,从容易得到的工业纯粗硼砂(主要成份可写成Na_2B_4O_7
A small amount of boric acid is often used in laboratories. Boric acid is a monovalent weak acid, Ka = 5.8 × 10 ~ (-10). . Boric acid slightly soluble in cold water, but more soluble in hot water. When the boric acid is neutralized with a strong base such as NaOH, the metaborate borate NaBO 2 is obtained in the concentrated alkali solution and the tetraborate NaB 4 O 5 (OH) 4 · 8H 2 O is obtained in the dilute alkali solution. In turn, however, boric acid H 3 BO 3 is always obtained when acid is added to any borate, since boric acid is easily precipitated from the solution due to its low solubility. We try to use these properties of boric acid from readily available industrial pure crude borax (the main component can be written as Na_2B_4O_7