Trimethylolpropane for industrial use (3)

4.

4.

4.

For each component containing a hydroxyl functional group in the sample, the hydroxyl content of the component is obtained by multiplying the content of the component by the mass fraction of the hydroxyl group in the component, and the hydroxyl content of each component is added to obtain the hydroxyl content of the sample

4.

The mass fraction of hydroxyl group w ₁ , the value is expressed in %, calculated according to formula (2):

w ₄ =w ₁ ×0.

Where:

w ₁ —The value of the mass fraction of trimethylolpropane measured in accordance with 4.

w ₂ —The value of the mass fraction of ditrimethylolpropane measured in accordance with 4.

w ₃ —The value of the mass fraction of cyclic trimethylolpropane formal measured in accordance with 4.

0.

0.

0.

4.

4.

Under the catalysis of pyridine, trimethylolpropane quantitatively reacts with acetylation reagent at (90～100)℃ to produce ester and acetic acid.

4.

4.
3.
2.
2.
1 Sodium hydroxide standard titration solution: c(NaOH)=1mol/L
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4.
3.
2.
2.
2 Acetylation reagent: mix 10 mL of acetic anhydride and 90 mL of pyridine, put them in a closed bottle, and store in the dark
.
This reagent is configured at the time of use
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4.
3.
2.
2.
3 Phenolphthalein indicator solution: 10g/L
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4.
3.
2.
3 Instruments

4.
3.
2.
3.
1 Flat bottom flask with ground mouth: 200mL
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4.
3.
2.
3.
2 Straight glass condenser tube: with ground mouth, length (750～1000)mm
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4.
3.
2.
3.
3 Thermal bath: oil bath or water bath, control the temperature at (90～100)℃
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4.
3.
2.
4 Analysis steps

Weigh about 0.
6g of laboratory sample, accurate to 0.
0002g, place it in a flat-bottomed flask, add 20.
00mL acetylation reagent with a pipette, install a straight glass condenser, and seal the connection with 1 to 2 drops of pyridine.
The flat-bottomed flask was half immersed in a hot bath at (90～100)℃, and heated to reflux for 90min under frequent shaking
.

Take out the flat-bottomed flask from the hot bath, add 20mL of water to rinse the condenser while cooling in a cold water bath below 5°C, add 2 to 3 drops of phenolphthalein indicator solution after cooling to room temperature, and titrate with sodium hydroxide standard titration solution until the solution is It is reddish and will not fade for 15s
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At the same time of the measurement, follow the same steps as the measurement, do a blank test with the same amount of reagent solution without adding the sample
.

4.
3.
2.
5 Result calculation

The mass fraction of hydroxyl group w ₅ , the value is expressed in %, calculated according to formula (3):

Where:

V ₁ —The value of the volume of the sodium hydroxide standard titration solution (4.
3.
2.
2.
1) consumed in the blank test, in milliliter (mL);

V ₂ —The value of the volume of the standard titration solution (4.
3.
2.
2.
1) of sodium hydroxide consumed by the sample, in milliliter (mL);

c—The exact value of the concentration of sodium hydroxide standard titration solution, the unit is moles per liter (mol/L);

m—the value of the mass of the sample, in grams (g);

M—The value of the molar mass of the hydroxyl group, in grams per mole (g/mol) (M=17.
01)
.

Take the arithmetic average of the two parallel determination results as the report result, and the absolute difference between the two parallel determination results shall not exceed 0.
2%
.