铋盐-钼蓝示差光度法测定磷矿石中五氧化二磷

采用硝酸、盐酸溶矿,用高氯酸将偏磷酸氧化为正磷酸,在铋盐催化下磷与钼酸铵反应生成黄色磷钼酸铵,此磷钼酸铵能被抗坏血酸还原为磷钼蓝,以示差光度法直接测定.其最大吸收波长为700nm,表观摩尔吸光系数为1.60×10⁵L/(mol·cm),磷在3～5μg/mL范围内符合比耳定律,试样加标回收率为97.10%～100.86%,9次测定的相对标准偏差为1.08%～4.66%.适用于磷矿石中5%～38%五氧化二磷的测定.

Determination of Phosphorus Pentoxide in Phosphate Ore by Bismuth Salt-molybdenum Blue Parallax Photometric Method

Phosphate ore sample was dissolved with nitric acid and chlorhydric acid. Metaphosphoric acid in solution was oxided into ortho-phosphoric acid. Reacting with ammonium molybdate under the catalyst of bismuth salt, phosphorus transferred yellow ammonium phosphomolybdate. The ammonium phosphomolybdate was reducted into phosphomolybdenum blue. Then the contents of phosphorus were determined with parallax photometric method. The maximum absorbance is at 700 nm with an apparent molar absorptive of 1.60×10⁵L/(mol·cm). Beer's law is obeyed in the phosphorus concentration range of 3～5 μg/mL. The recovery was in the range of 97.10%～100.86% while the relative standard deviation was in the range of 1.08%～4.66%. The method is suited to determine the phosphorus pentoxide contents with the range of 5%～38% in phosphate ores.