GB/T 20975.31-2019Methods for chemical analysis of aluminium and aluminium alloys—Part 31: Determination of phosphorus content—Molybdenum blue spectrophotometry (English PDF)

Foreword

GB/T 20975, Methods for chemical analysis of aluminium and aluminium alloys, is divided into 31 parts:

-- Part 1: Determination of mercury content;

-- Part 2: Determination of arsenic content;

-- Part 3: Determination of copper content;

-- Part 4: Determination of iron content - Orthopenanthroline photometric method;

-- Part 5: Determination of silicon content;

-- Part 6: Determination of cadmium content - Flame atomic absorption spectrometric method;

-- Part 7: Potassium periodate spectrophotometric method;

-- Part 8: Determination of zinc content;

-- Part 9: Determination of lithium content - Flame atomic absorption spectrometric method;

-- Part 10: Determination of tin content;

-- Part 11: Determination of tin content;

-- Part 12: Determination of titanium content;

-- Part 13: Determination of vanadium content - N-bezoyl-Nphenylhydroxylamine spectrophotometric method;

-- Part 14: Determination of nickel content;

-- Part 15: Determination of boron content;

-- Part 16: Determination of magnesium;

-- Part 17: Determination of strontium content - Flame atomic absorption spectrometric method;

-- Part 18: Determination of chromium content;

-- Part 19: Determination of zirconium content;

Caution -- The personnel who uses this Part shall have hands-on experience in formal laboratory work. This Part does not address all possible security issues. It is the responsibility of the user to take appropriate safety and health measures and to ensure compliance with the conditions which are set by the relevant national regulations.

1 Scope

This Part of GB/T 20975 specifies the method for the determination of phosphorus in aluminum and aluminum alloys by molybdenum blue spectrophotometry.

This Part applies to the determination of phosphorus content in aluminum and aluminum alloys. The measurement range is: 0.0001% ~ 0.05%.

2 Normative references

The following documents are indispensable for the application of this document.

For dated references, only the dated version applies to this document. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 6682, Water for analytical laboratory use. Specification and test methods

GB/T 8170-2008, Rules of rounding off for numerical values & expression and judgement of limiting values

3 Method summary

Use nitric acid and hydrochloric acid to dissolve the sample; heat the perchloric acid to remove the hydrochloric acid; use potassium permanganate to oxidize into orthophosphoric acid; in the nitric acid medium of 0.8 mol/L ~ 1.2 mol/L, orthophosphoric acid and ammonium molybdate form phosphorus

5 Instruments

Spectrophotometry.

6 Sample

Process the sample into chippings of no more than 1 mm.

7 Analysis steps

8 Result calculation

Calculate the phosphorus mass fraction according to Formula (1):

Where: m2 -- the phosphorus content of the test solution that is found on the working curve, in milligrams (mg); m1 -- the phosphorus content of the blank test solution of the accompanied test sample that is found on the working curve, in milligrams (mg);

T -- dilution ratio, see Table 1; m0 -- sample mass, in grams (g).

8.2 When the phosphorus content is < 0.01%, express the calculation result to four decimal places; when the phosphorus content is >=0.01%, express the calculation result to three decimal places. The rounding-off value is based on 3.2 and 3.3 of GB/T 8170-2008.

9 Precision