1 Subject Content and Application Scope
This standard specifies the determination of phosphorus content by molybdenum blue spectrophotometric method.
This standard is applicable to the determination of phosphorus content in limestone products for chemical industry and the determination range is 0.001%~0.2%.
2 Normative References
GB 6682 Water for Analytical Laboratory Use - Specification and Test Methods
GB/T 9721 Chemical Reagent - General Rules for the Molecular Absorption Spectrophotometry (Ultraviolet and Visible)
3 Method Summary
Decompose the specimen with nitric acid and perchloric acid; in hydrochloric acid medium, restore the generated phosphorus-molybdenum heteropoly acid into phosphomolybdenum blue; then, measure the absorbance at spectrophotometer wavelength of 680 or 780nm.
4 Reagents and Solutions
Water used in this standard shall conform to the specification of Grade 3 water specified in GB 6682; unless otherwise specified, the adopted reagents refer to analytical reagents.
4.1 Nitric acid (GB 626).
4.2 Perchloric acid (GB 623).
4.3 Hydrobromic acid (GB 621).
4.4 Hydrochloric acid (GB 622) solution: 1+2.
4.5 Hydrochloric acid solution: 1+6.
4.6 Sodium hydroxide (GB 629) solution: 200g/L.
4.7 Ammonium molybdate [(NH4)6Mo7O24•4H2O](GB 657) solution: 20g/L.
4.8 Ascorbic acid solution: 20g/L (prepared right before use).
1 Subject Content and Application Scope
2 Normative References
3 Method Summary
4 Reagents and Solutions
5 Apparatus
6 Specimen
7 Analytical Procedures
8 Plotting of Working Curve
9 Expression of Analysis Results
10 Allowable Difference
Additional Information
