Industrial neopentyl glycol (2)

4 Test method

The reagents and water used in this standard refer to analytical reagents and distilled water or water of corresponding purity unless other requirements are indicated

4.

4.

4.

4.

4.

4.

Under the catalysis of pyridine, neopentyl glycol undergoes quantitative acetylation reaction between its hydroxyl groups and acetic anhydride to produce esters and acetic acid .

4.

a.

b.

c.

4.

Constant temperature water bath or glycerin bath and general laboratory equipment

4.

Weigh 0.

4.
2.
1.
5 Calculation of analysis results

The mass percentage X _{1 of} hydroxyl is calculated according to formula (1):

Where: c— the actual concentration of sodium hydroxide standard titration solution, mol/L;

V ₀ —Blank consumption volume of sodium hydroxide standard titration solution, mL;

V—The volume of the standard titration solution of sodium hydroxide consumed by the sample, mL;

m—the mass of the sample, g;

0.
01701—The hydroxyl mass expressed in grams, which is equivalent to 1.
00mL sodium hydroxide standard titration solution [c(NaOH)=1.
000mol/L]
.

Take the arithmetic mean value as the measurement result
.

4.
2.
1.
6 Tolerance

The difference between the two parallel determination results shall not be more than 0.
2%
.

4.
2.
2 Acetic anhydride-sodium acetate method

4.
2.
2.
1 Principle of the method

Under the catalysis of sodium acetate, the hydroxyl groups of neopentyl glycol quantitatively react with acetic anhydride to generate esters and acetic acid.
The hydroxyl content is calculated from the amount of acetic anhydride consumed
.

4.
2.
2.
2 Reagents and solutions

a.
Anhydrous sodium acetate ;

b.
Acetic anhydride ;

c.
Phenolphthalein indicator solution: 10g/L;

d.
Sodium hydroxide standard titration solution: c(NaOH)=1mol/L
.

4.
2.
2.
3 Apparatus or equipment

a.
General laboratory equipment;

b.
Flat electric furnace: 500 or 800W;

c.
Straight tube air condenser;

d.
Voltage regulator: 1kV;

e.
Micro burette: 3mL;

f.
Hard glass test tube: 50mL
.

4.
2.
2.
4 Analysis steps

Weigh about 0.
7g (accurate to 0.
0002g) of the ground and mixed sample into a dry test tube, add 0.
4g (accurate to 0.
1g) of anhydrous sodium acetate and add 2.
000mL of acetic anhydride with a microburet Air condensing tube, put the test tube on the preheated electric furnace (adjust the voltage regulator to 100～120V to preheat for 10 minutes), slowly heat it to a slight boiling point, and wait for the solid matter in the tube to disappear completely (except for the blank).
Remove the test tube and cool it to near room temperature.
Wash the reactant with 40-50mL of water into a 250mL Erlenmeyer flask, place for 30min, add 2 drops of phenolphthalein, titrate with sodium hydroxide standard titration solution to reddish and keep it for 30s without fading.
The end
.
Do a blank test at the same time
.

4.
2.
2.
5 Calculation of analysis results

The mass percentage of hydroxyl group X _{2 is} calculated according to formula (2):

In the formula: c—the actual concentration of the sodium oxychloride standard titration solution, mol/L;

V ₀ —Blank consumption volume of sodium hydroxide standard titration solution, mL;

V—The volume of the standard titration solution of sodium hydroxide consumed by the sample, mL;

m—the mass of the sample, g;

0.
01701—The hydroxyl mass expressed in grams, which is equivalent to 1.
00mL sodium hydroxide standard titration solution [c(NaOH)=1.
000mol/L]
.

Take the arithmetic mean value as the measurement result
.

4.
2.
2.
6 Allowable difference

The difference between the two parallel determination results shall not be more than 0.
2%
.