Industrial Acetanilide (3)

4.

Weigh 0.

a.

b.

Insert the tip of the burette into the 2/3 place below the liquid surface, titrate quickly with sodium nitrite standard titration solution at 10～25℃ under stirring to near the end point, lift the tip of the burette out of the liquid surface, rinse with a small amount of water, and continue under vigorous stirring Slowly titrate until a small amount of solution is dipped in a glass rod to immediately make the starch potassium iodide indicator solution appear blue.

4.

The industrial acetanilide mass percentage X1 is calculated according to formula (1):

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

V ₁ —The volume of sodium nitrite standard titration solution consumed by the titration sample, mL;

V ₀ —The volume of sodium nitrite standard titration solution consumed by the blank test, mL;

m—the mass of the sample, g;

0.

x ₂ —The aniline content determined in accordance with Article 4.

1.

Take the arithmetic mean as the test result

4.

The difference between the two parallel determination results is not more than 0.

4.

According to the provisions of GB617

4.

4.
4.
1 Principle of the method

Aniline and sodium nitrite quantitatively undergo a diazotization reaction under acidic conditions, and the aniline content is calculated based on the amount of sodium nitrite consumed
.

4.
4.
2 Reagents and solutions

4.
4.
2.
1 Potassium bromide ;

4.
4.
2.
2 Hydrochloric acid solution: 1+3;

4.
4.
2.
3 Ethanol ;

4.
4.
2.
4 Sodium nitrite standard titration solution: c(NaNO ₂ )=0.
05mol/L;

4.
4.
2.
5 Starch potassium iodide indicator (same as 4.
2.
2.
4)
.

4.
4.
3 Analysis steps

Weigh 1.
5g (accurate to 0.
0002g) sample, place it in a 400mL beaker, add 10mL ethanol to dissolve, add 250mL water to dilute, add 10mL hydrochloric acid solution and 0.
5g potassium bromide, put on a magnetic stirrer to dissolve
.

Insert the tip of the burette into about 2/3 below the liquid surface, and quickly titrate with sodium nitrite standard titration solution at 10～25℃ to near the end point under stirring.
Lift the tip of the burette up to the liquid surface and rinse with a small amount of water.
Continue to slowly under vigorous stirring.
Titrate until a small amount of solution is dipped in a glass rod, and immediately make the starch potassium iodide indicator blue.
After stirring for 1 min, the end point is the blue color
.
Do a blank test at the same time
.

4.
4.
4 Representation and calculation of results

The mass percentage X _{2 of} aniline in industrial acetanilide is calculated according to formula (2):

Where:

c ₁ —The actual concentration of sodium nitrite standard titration solution, mol/L;

V ₂ —The volume of sodium nitrite standard titration solution consumed by the titration sample, mL;

V ₀ —The volume of sodium nitrite standard titration solution consumed by the blank test , mL;

m—the mass of the sample, g;

0.
09312— The mass of aniline expressed in grams is equivalent to 1.
00mL sodium nitrite standard titration solution Cc(NaNO ₂ )=1.
000mol/L]; the arithmetic mean is used as the test result
.

4.
4.
5 Allowance

The difference between the two parallel determination results is not more than 0.
03%
.