Base number (also known as total base number, TBN) The amount of acid used for titration 1g sample to the end of titration is expressed in mg/g(KOH).
The amount of acid used when strongbasenumber (SBN) neutralizes the strongly alkaline components in 1g sample is expressed in mg/g(KOH).
Overview of methods
Dissolve the sample in a titration solvent and titrate it with potassium hydroxide or isopropanol hydrochloride solution on a potentiometric titrator. Draw the titration volume with potentiometer reading, and take the abrupt point of the curve as the titration end point.
Instruments and equipment
The potentiometric titrator can be operated manually or automatically, and has the functions of timing and quantitative dropping.
Glass electrode.
calomel electrode
reagent
Titration solvent (for acid value determination) Add 500 ml of toluene, 250 ml of tetrahydropyran and 5 ml of water into 245 ml of isopropanol and mix well. Blank values should be determined before daily use.
Titration solvent (used to measure alkali value) In brown reagent bottle, add 30mL of water to 1L isopropanol and mix thoroughly, then add 1L toluene and 1L chloroform and mix thoroughly.
The standard solutions of potassium hydroxide and isopropanol are 0. 1mol/L and 0.2mol/L, and the concentrations should be calibrated accurately.
The standard solution of isopropanol hydrochloride is 0. 1mol/L and 0.2mol/L, and the concentration should be calibrated accurately.
Potassium chloride electrolyte saturates potassium chloride aqueous solution.
Buffer solution (pH 4.00) Weigh 10.2 1g potassium hydrogen phthalate, dissolve it in fresh distilled water and dilute it to1L.
Buffer solution (pH 9. 18) Weigh 3.80g borax, dissolve it in distilled water and dilute it to1L.
Weigh 24.20 g of 2,4,6-trimethylpyridine and put it into a 1 liter volumetric flask containing 100 ml of isopropanol. Then measure the standard solution of isopropanol hydrochloride (c 1 is the calibration substance concentration), add it into the volumetric flask under constant shaking, dilute it with isopropanol to the scale of the volumetric flask, and mix it evenly for use (valid for two weeks).
Weigh 27.8 g of 0. 1 g m-nitrophenol from the mother liquor b of the buffer solution, and add it into a 1 liter volumetric flask containing 100 ml isopropanol. Measure the standard solution of potassium hydroxide and isopropanol with a 250mL measuring cylinder (c2 is the accurate concentration of the standard solution calibrated by potassium hydroxide and isopropanol), add it into a volumetric flask under constant shaking, dilute it with isopropanol to scale, and mix well. The service period is two weeks.
Non-aqueous acidic buffer solution Take 100mL buffer solution mother liquor A and add it into 100ml titration solvent, and the validity period is lh.
Non-aqueous alkaline buffer solution Take 100mL buffer solution mother liquor B and add it into 100ml titration solvent, and the validity period is lh.
Analytical method
1) calibrate the instrument. Turn on the power supply of the instrument and stabilize 1/2h. According to the instructions of potentiometric titrator, calibrate the instrument with buffer solutions of pH4.00 and pH9. 18.
2) Potential measurement of non-aqueous buffer solution. Put the electrode into the non-aqueous acidic and alkaline buffer solution in turn, and stir for 5 minutes. The temperature difference between the solution and the titrated sample should not be greater than 2℃. Read the potential value of each solution as the titration end point of the titration curve without inflection point.
3) Determine the acid value of the sample. According to the strength of the acid value or alkali value of the sample, weigh an appropriate amount of the sample in a beaker of 150mL, add 100mL titration solvent, put it on a potentiometric titrator, and stir until the sample is completely dissolved. Record the initial reading of potentiometer, and titrate with 0. 1mol/L potassium hydroxide isopropanol standard solution at the speed of 0.2mL/min under stirring. When the potential value of 0. 1mL is changed to 30mV (equivalent to 0.6pH) each time, the titration speed should be slowed down to 0.05mL/min to titrate to potential jump or non-water measured in step 2). After titration, wash the electrode with solvent and soak it in distilled water for later use. According to the sample determination steps, titrate the blank value of 100mL titration solvent.
4) Determination of total base value and strong base value of the sample. According to the operation in step 3), titrate with 0. 1mol/L hydrochloric acid isopropanol standard solution until the potential jumps or reaches the potential value of the non-aqueous acidic buffer solution measured in step 2).
5) Calculation of total acid value (mg/g, KOH) of the sample:
Investigation and analysis technology of resources and environment in the fourth volume of rock mineral analysis
Where: A is the volume of 0. 1mol/L potassium hydroxide isopropanol standard solution or the potential value of non-aqueous alkaline buffer solution, ml; B is the volume of 0. 1mol/L potassium hydroxide isopropanol standard solution for blank test, ml; C2 is the standard solution concentration of potassium hydroxide and isopropanol, mol/l; M is the mass of the sample, g; 56. 1 is the molar mass value of potassium hydroxide, and the unit is g/mol.
6) Calculate the total base value or strong base value (mg/g, KOH) of the sample:
Investigation and analysis technology of resources and environment in the fourth volume of rock mineral analysis
Where: a is the volume of isopropanol hydrochloride standard solution consumed at the end of titration, and the potential value of non-aqueous acidic buffer solution, ml; B is the blank value corresponding to a, ml; C 1 is the concentration of isopropanol hydrochloride standard solution, mol/l; M is the mass of the sample, g; C is the volume of isopropanol hydrochloride standard solution consumed when titrating the sample to the potential of non-aqueous alkaline buffer solution, ml; D is the volume of standard solution of potassium hydroxide and isopropanol consumed in blank titration, corresponding to the end point of c, ml; C2 is the concentration of standard solution of potassium hydroxide and isopropanol, mol/L.