GB/T 223.62-1988Methods for chemical analysis of iron,steel and alloy--The butyl acetate extraction photometric method for the determination of phosphorus content (English PDF)

2.24 Standard phosphorus solution

2.24.1 Take 0.4393g of reference potassium dihydrogen phosphate (KH2PO4) (pre-dried at 105°C to constant weight); dissolve by appropriate amount of water; add 10ml of nitric acid (rho 1.42g/ml); transfer into 1000ml volumetric flask; use water to dilute to the scale; shake evenly. 1ml of such solution contains 100µg of phosphorus.

2.24.2 Pipette 20.00ml of standard phosphorus solution (2.24.1); place into 1000ml volumetric flask; add 5ml of nitric acid (rho 1.42g/ml); add water to dilute to the scale, shake evenly. 1ml of such solution contains 2µg of phosphorus.

3.1 Specimen quantity

Weigh the specimens as per Table 1.

3.2 Blank test

Do the blank test accompanied by the specimen.

3.3 Determination

3.3.1 Specimen solution

3.3.1.1 General specimen

Place the specimen (3.1) into the conical flask; add nitric acid as per Table 1; heat and dissolve [the insoluble specimen can be added 10~15ml of hydrochloric acid (2.8) for assisting dissolving]; add perchloric acid as per Table 1; heat, vaporize and smoke till the internal conical flask is transparent and back-flows for 5~6min (if the specimen contains more than 2% manganese; add another 7~8ml of perchloric acid; vaporize and smoke till the internal conical flask is transparent and back-flows for 20~25min); vaporize till nearly dry; cool off.

3.3.1.2 Specimen with more-than-50g chromium content

According to the solution specimen in 3.3.1.1, vaporize till smoke; after chromium is oxidized into hexavalent; add 2~3ml of hydrochloric acid (2.8) to volatilize chromium; repeat the operation for 2~3 times; continue to vaporize till the internal conical flask is transparent and back-flows for 3~4min; vaporize again till nearly dry; cool off.

3.3.1.3 Specimen with excessive-content of arsenic

Vaporize the solution specimen till smoke according to 3.3.1.1; cool off slightly; add 10ml of hydrochloric acid (2.8), 5ml of hydrobromic acid (2.6) to expel the arsenic; continue to heat till the internal conical flask is transparent and back-flows 3~4min; vaporize again till nearly dry; cool off.

3.3.2 Salts dissolvement and interfering elements treatment

3.3.2.1 General specimen

Add 30ml of nitric acid (2.10); heat and dissolve salts; titrate sodium nitrite solution (2.17) till chromium is reduced to low-valent and continue to titrate for several excessive drops; boiling it to remove nitrogen oxide; cool off to the room temperature.

Transfer the solution into 100ml volumetric flask; dilute with water to the scale; mix evenly.

3.3.2.2 Tungsten-containing specimen

Use 20ml of water to dissolve the salts obtained from 3.3.1; add 10ml beryllium sulfate solution (2.21), 10ml of EDTA solution (2.22), 2g of oxalic acid (2.1); use ammonium hydroxide (2.14) to neutralize till pH is 3~4; dilute with water to about 90ml; boiling for 2~3min; then add 10ml of ammonium hydroxide (2.14); boiling for 1min; cool off to the room temperature; filter the solution; wash by ammonium hydroxide (2.15); use water to wash the precipitation into the original conical flask; add 30ml of nitric acid (2.10) to dissolve the precipitation remained on the filter paper; discard the filter paper after cleaning; then follows the procedures from titrating sodium nitrite solution (2.17) in 3.3.2.1.

3.3.2.3 Zirconium-containing specimen

Perform as per 3.3.2.1 till after cooling off to the room temperature; add 5ml of hydrofluoric acid (2.13), shake evenly; add 20ml of boric acid solution (2.18); then transfer the solution into 100ml volumetric flask; dilute with water to the scale; mix evenly.

3.3.2.4 Specimen containing titanium, niobium, zirconium, tantalum

Add 10ml of water and 15ml of sulfuric acid (2.12) to dissolve the salts obtained from 3.3.1; titrate sodium nitrite solution (2.17) to reduce to hexavalent chromium; then boiling and remove the nitrogen oxide; take off; add 5ml of hydrofluoric acid (2.13) when it is hot; shake evenly; cool off to the room temperature. Transfer the solution into 100ml volumetric flask; dilute with water to the scale; mix evenly.

Transfer 10.00ml of specimen solution to place into 60ml separating funnel; add 0.4~0.8g of copper and iron reagents (2.2), 20ml of chloroform (2.5); vibrate for 1min; after standing and layering, discharge the organic phase; add 1ml of copper and iron reagent solution (2.23), 10ml of chloroform (2.5) into aqueous solution; vibrate for 40s; after standing and layering, discharge organic phase; then add 10ml of chloroform (2.5); vibrate for 30s; after standing and layering, discharge organic phase [if the copper and iron reagent has not been cleaned completely yet, then use chloroform (2.5) to clean again]; add 0.04~0.1g of boric acid (2.3), 1ml of nitric acid (2.11); vibrate for 10~15s. Then follow the procedures from adding 15ml of butyl acetate (2.4) in 3.3.3.2.

NOTE: for the specimen containing tungsten, titanium, niobium, tantalum, zirconium, firstly, treat the tungsten-containing specimen; then treat the specimen containing titanium, niobium, tantalum, zirconium.

3.3.3 Coloration

3.3.3.1 Transfer 10.00ml of specimen solution from the solution obtained from 3.3.2.1 or 3.3.2.2 or 3.3.2.3 into 60ml separating funnel. […]