GB/T 2432-1981Gasoline--Determination of tetraethyl lead content. Complexometric titration method (English PDF)

3.1 Hydrochloric acid. analytically pure, formulated into 6N hydrochloric acid aqueous

solution.

3.2 Ammonia. analytically pure.

G – weight of zinc particles, in g;

65.38 - grams of zinc per gram of molecule.

4.2 Preparation and calibration of 0.02M ethylenediaminetetraacetic acid disodium

standard solution.

4.2.1 Preparation. take 8g of ethylenediaminetetraacetic acid disodium; dissolve it in 1000mL of distilled water; and mix well.

4.2.2 Calibration. accurately take 25mL of ethylenediaminetetraacetic acid disodium

standard solution in a conical flask; add 5~6 drops of 0.5% xylenol orange aqueous solution; adjust the solution to a pink color by ammonia water. Then use the 6N hydrochloric acid aqueous solution to adjust it into bright yellow; and then add 0.5 mL of 6N hydrochloric acid aqueous solution; add 1.5~2.0g of hexamethylenetetramine;

and immediately titrate by a 0.02M zinc chloride standard solution until the solution turns from yellow to pink, which shall be regarded as the end point.

The molar concentration, M3, of the ethylenediaminetetraacetic acid disodium standard solution is calculated according to Formula (3).

Where.

M2 – molar concentration of zinc chloride standard solution;

V1 – volume of zinc chloride standard solution consumed by titration, in mL;

25 – volume of the measured ethylenediaminetetraacetic acid disodium standard solution, in mL.

Perform each calibration at least for three times; and the difference among the results of each measurement shall not exceed 0.2% of the arithmetic mean; otherwise it must be discarded.