A photometric determination of phosphorus in copper metal and its alloy with molybdenum blue has been investigated.
0.25 to 1 g of the sample is decomposed with 10 to 20 m
l of nitric acid (1+1) and 5 ml of hydrochloric acid. 15 m
l of perchloric acid is added, and it is evaporated until nitric acid is romoved by occuring strong fumes of perchloric acid.
After cooling, the solution is diluted to approximately 60 m
l with water. Copper interference may be removed by electrolysis as a mercury cathode in diluted perchloric acid solution.
After the electrolytic separation, micro amount of phosphorus is enriched in the form of precipitates of ferric phosphate by adding 50 mg of ferric iron as a coprecipitant using ammonia water (1+1) in the presence of ammonium chloride.
After removing the interfering elements, it is colored as molybdenum blue with hydrazine sulfate as a reducing agent in 1
N of sulphric acid solution. The absorbance is measured at 825 mμ.
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