关于高碳铬铁中铬的测定,过去一直都采用过氧化钠熔融法,并且也曾经被认为是最好的方法。但在实际操作中,步骤较多,费时也长,达不到快速要求。再在熔融所需坩埚的选择也不无困难,一般采用铁、镍或瓷坩埚,但瓷坩埚的灼烧温度不能太高,一般只能在600℃左右,因此熔融时间较长;铁坩埚一般含微量的铬;用镍坩埚,则目前又是缺镍的时候,故都不适合。因此曾考虑省去熔融,直接用酸溶解,仿低碳铬铁用稀硫酸(1:4)溶解,但作用不能完全,只能适用于含碳量1.5%以下的。改用磷酸(比重1.70)加热至250℃左右可完全溶解,仅有极微量硅酸物残留,但需时较长。若采用硫磷混合酸,则效力低于单独使用硫酸或磷酸。由于二氧化硅虽能溶于磷酸,但受硫酸脱水而析出沉淀,如此阻碍了铬铁细粒的被溶解,虽可加氟化钠促使溶解,但有蒸出白烟等麻烦。故现在采用硫酸(1:1)先 The determination of chromium in high-carbon ferrochromium has historically been based on sodium permanganate melting and has also been considered as the best method. However, in actual operation, there are many steps, which take a long time and can not meet the rapid requirements. Then the choice of melting crucible is not without difficulty, generally using iron, nickel or porcelain crucible, but the firing temperature of porcelain crucible can not be too high, usually only about 600 ℃, so the melting time longer; iron crucible general Containing traces of chromium; nickel crucible, then the current lack of nickel, it is not suitable. It has been considered eliminating the need for melting, dissolved directly with acid, imitation low-carbon ferrochromium with dilute sulfuric acid (1: 4) dissolved, but the role can not be completely applied only to carbon content below 1.5%. Switch to phosphoric acid (specific gravity 1.70) heated to about 250 ℃ can be completely dissolved, only a trace amount of silicate residue, but takes longer. If the use of mixed phosphoric acid, the effectiveness is lower than the use of sulfuric acid alone or phosphoric acid. Although silica is soluble in phosphoric acid, it is precipitated by the dehydration of sulfuric acid and hindered the dissolution of ferrochromium fine particles. Although sodium fluoride can be dissolved to promote dissolution, there are troublesome problems such as steamed white smoke. So now using sulfuric acid (1: 1) first