ASTM D2896 for base number of petroleum products
ASTM D2896 for base number of petroleum products by potentiometric perchloric acid titration
8. Standardization of Reagents
8.1 Perchloric Acid Solution - The standardization of the perchloric acid solution (HClO4) differs for the two procedures as follows:
8.1.1 Procedure A (120 mL) - Heat a quantity of potassium hydrogen phthalate in an oven at 120°C for 2 h and allow it to cool. Take 0.1 to 0.2 g of the potassium hydrogen phthalate weighed to the nearest 0.1 mg and dissolve it in 40 mL of warm glacial acetic acid. Add 80 mL of chlorobenzene, cool, and titrate with 0.1 N HClO4 solution, using the electrode system and procedures given in 10.1 to 10.4 and 11.4 to 11.7. Detect the end point by the same procedure used for base number determination (see 14.2). Carry out a blank titration on 40 mL of glacial acetic acid plus 80 mL of chlorobenzene (see 11.8).
8.1.2 Procedure B (60 mL) - Heat a quantity of potassium hydrogen phthalate in an oven at 120°C for 2 h and allow it to cool. Take 0.05 to 0.1 g of the potassium hydrogen phthalate weighed to the nearest 0.1 mg and dissolve it in 20 mL of warm glacial acetic acid. Add 40 mL of chlorobenzene, cool, and titrate with 0.1 N HClO4 solution as described in 8.1.1. Carry out a blank titration on 20 mL of glacial acetic acid and 40 mL of chlorobenzene (see 11.8).
8.1.3 Calculate the normality, N(A), of the HClO4 solution as follows:
N(A) = 1000W/[204.23•(V–b)]
where:
W = potassium hydrogen phthalate, g,
V = HClO4 solution used, mL, and
b = volume corresponding to V for the blank titration, mL.
NOTE 7 - Because of the relatively large coefficient of volumetric expansion of organic liquids, the acetous HClO4 solution should be used within more or less 5°C of the temperature at which it was standardized. If used at a temperature more than 5°C higher, multiply the volume used by the factor 1 - (t•0.001). If used at a temperature more than 5°C lower, multiply by the factor 1 + (t•0.001), where tis the difference in degrees Celsius between temperatures of standardization and use and is always positive.
8.2 Sodium Acetate Solution - The standardization of the sodium acetate solution (Na2CO3) differs for the two procedures as follows:
8.2.1 Procedure A (120 mL) - Use 120 mL of titration solvent and 8.00 mL of 0.1 NHClO4 solution. Titrate with 0.1 N sodium acetate solution, using the electrode system and procedure given in 10.1 to 10.4 and 11.4 to 11.7. Detect the end point by the same procedure as will be used for base number determination (see 14.2). Calculate the normality, N(B), of the sodium acetate solution as follows:
N(B) = [(8.00–b)N(A)]/G
where:
b = volume corresponding to V for the blank titration,
N(A) = normality of the HClO4 solution, and
G = volume of standard sodium acetate used in the standardization, mL.
8.2.2 Procedure B (60 mL) - Use 60 mL of titration solvent and 4.00 mL of 0.1 N HClO4 solution. Titrate as described in 8.2.1. Calculate the normality, NB, of the sodium acetate solution as follows:
N(B) = [(4.00–b)N(A)]/G
where:
b= volume corresponding to V for the blank titration,
N(A) = normality of the HClO4 solution, and
G = volume of standard acetous sodium acetate used in the standardization, mL.
