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将生铁试样加入硫酸、磷酸、硝酸、高氯酸的混合溶液中,在高温下强冒烟,钒能定量氧化成五价,同时石墨碳也完全被破坏。试样中铬、锰等元素的干扰可用亚砷酸钠、亚硝酸钠消除。在9.8N硫酸、8N磷酸介质中,五价钒氧化二苯胺磺酸钠呈稳定的紫色化合物,借此进行钒的比色测定。 一、操作方法 称取生铁试样20mg,置于100ml锥形瓶中,加5ml溶样酸(15ml硫酸+20ml磷酸+9ml硝酸+15ml高氯酸+40ml水),加热溶解。冒烟至瓶口后继续加热至石墨碳反应完毕(小气泡完全平静),取下稍冷,加5ml亚砷酸钠(0.02％),煮沸,取下流水冷至室温。然后依次加2ml尿素(4％),二滴亚硝酸钠(0.2％)、2ml二苯胺磺酸钠(0.05％),摇匀。用2cm比色皿,以水作空白,于721型分光光度计波长540nm处测吸光度,由标准曲线查得钒含量。
Pig iron samples were added to sulfuric acid, phosphoric acid, nitric acid, perchloric acid mixed solution, strong smoke at high temperatures, vanadium can be quantitatively oxidized to pentavalent, while graphite carbon is completely destroyed. Sample chromium, manganese and other elements available interference sodium arsenite, sodium nitrite elimination. In 9.8N sulfuric acid, 8N phosphoric acid medium, pentavalent vanadium oxy diphenylamine sulfonate was a stable purple compound, whereby the colorimetric determination of vanadium. First, the method of operation Weigh the pig iron sample 20mg, placed in 100ml conical flask, add 5ml dissolved sample acid (15ml sulfuric acid + 20ml phosphoric acid + 9ml nitric acid + 15ml perchloric acid + 40ml water), heated to dissolve. Smoke to the bottle mouth and continue heating until the graphite carbon reaction is completed (small bubbles completely calm), remove the cold, add 5ml sodium arsenite (0.02%), boil, remove the cold water to room temperature. Then followed by adding 2ml of urea (4%), two drops of sodium nitrite (0.2%), 2ml sodium diphenylamine sulfonate (0.05%), shake. With 2cm cuvette, with water as a blank, at 721 spectrophotometer wavelength of 540nm at absorbance measured by the standard curve found vanadium content.