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2 Determination of acidity and alkalinity of standard titration solution using organic solvent as medium
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2.
1 Method summary
After the sample is properly processed, under the specified operating conditions, add an indicator or use a potentiometer or acid meter to indicate the end point, and titrate with an alkali standard titration solution or an acid standard titration solution to calculate the acidity or alkalinity of the sample
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2.
2 Reagents and solutions
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2.
2.
1 Standard titration solution of perchloric acid , glacial acetic acid medium
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2.
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2 Potassium hydroxide standard titration solution
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For different organic chemical products, according to the titration requirements, other acid or base standard titration solutions can also be used
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3 Apparatus
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1 Semi-micro burette, divided into 0.
10 mL, or micro burette, divided into 0.
02 mL
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2 Potentiometer or pH meter with corresponding electrodes.
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4 Analysis steps
Add a certain organic medium and indicator in a prescribed volume into the Erlenmeyer flask, and titrate to the end point with an alkali standard titration solution or an acid standard titration solution, excluding the volume of the consumption standard titration solution
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Transfer the neutralized organic medium to the separatory funnel and add the specified amount of sample, shake it well, stand still for layering, separate the extracted organic medium layer, add an appropriate amount of indicator or insert an electrode, Under the specified operating conditions, titrate to the end point with an alkali standard titration solution or an acid standard titration solution
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Record the volume of standard titration solution consumed
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3.
3 Determination of acidity and alkalinity of some liquid samples-direct titration
Add the specified amount of sample and indicator into the Erlenmeyer flask, and titrate to the end point with an alkali standard titration solution or an acid standard titration solution
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Record the volume of standard titration solution consumed
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3.
4 The indicator used when titrating the sample should be the same as the indicator used when calibrating the standard titration solution
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5 According to the different nature of organic chemical products, this standard stipulates that when the titration reaches the end point, the end point color of the indicator should remain unchanged for 15s or 30s
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4 Calculation of analysis results
The acidity x a (calculated by A) or alkalinity x b (calculated by B) of the sample is calculated by mass percentage, calculated as follows:
In the formula: A—represents an acidic substance;
B——represents a certain alkaline substance;
C—Concentration of base standard titration solution or acid standard titration solution used in titration, mol/L;
V—volume of alkali standard titration solution or acid standard titration solution consumed during titration, L;
M— The mass of substance A or substance B in grams equivalent to 1.
00L alkali or acid standard titration solution [c(OH - )=1.
000mol/L or c(H + )=1.
000mol/L], g;
m——the mass of the sample, g;
When the sampling volume is measured by volume, m=p t V t , where:
V t -the volume of the sample at the test temperature, mL; p t -the density of the sample at the test temperature: g/cm 3
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Take the arithmetic mean of the two parallel determination results as the determination result
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When the acidity or alkalinity is not more than 0.
05%, the relative deviation of the two parallel determination results is not more than 20%
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When the acidity or alkalinity is not more than 0.
5%, the relative deviation of the two parallel determination results is not more than 10%
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When the acidity or alkalinity is not more than 1.
5%, the relative deviation of the two parallel determination results is not more than 5%
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