Industrial dicyandiamide (2)

4 Test method

The reagents and water used in this standard refer to analytical reagents and tertiary water specified in GB/T6682 when other requirements are not specified

The standard titration solutions, preparations and products used in the test are prepared in accordance with GB/T601 and GB/T603 unless other requirements are specified

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In the presence of a catalyst , the sample is decomposed with sulfuric acid to convert the nitrogen in the sample into ammonium sulfate , and sodium hydroxide is added to alkalize the reaction product

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Mix 1g/1 methine blue ethanol solution and 1g/L methyl red ethanol solution in a volume ratio of 1+2

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2 Distillation instrument: The assembly diagram is shown in Figure 1
.

Figure 1 Assembly drawing of distillation apparatus

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4 Analysis steps

Take an appropriate amount of sample and dry it at 105℃～110℃ for 3h, put it in a desiccator to cool to room temperature and grind it
.
Weigh 0.
3g of the above sample (accurate to 0.
0002g), place it in a 500mL Kjeldahl flask, add 5g potassium sulfate , 0.
25g anhydrous copper sulfate , add 10mL sulfuric acid along the bottle wall , and rinse the powder attached to the bottle wall to the bottle In
.

Place the Kjeldahl flask at an incline in a fume hood and slowly heat it to keep the temperature of the solution below the boiling point.
After the foam stops, gradually increase the temperature and keep it boiling for 1 hour
.
After cooling, slowly add 200 mL of water and shake well
.
Slowly add 60 mL of sodium hydroxide solution along the bottle wall to form a liquid layer by itself
.

Install the distillation device according to Figure 1 so that the lower end of the condenser tube 2 just touches the bottom of the 500mL Erlenmeyer Flask 1.
In the Erlenmeyer Flask 1, 100 mL of boric acid solution and three drops of methyl red-methine blue mixed indicator liquid are placed in advance
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Use pH test paper to test when heating to distill out 2/3 of the liquid.
If it is neutral, stop the distillation
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Rinse the inner wall and lower mouth of the condenser tube 2 with water, and the washing water is collected in the conical flask 1
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Titrate with a standard hydrochloric acid titration solution until the solution turns from green to grayish purple as the end point
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Do a blank test at the same time
.

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5 Expression of analysis results

The dicyandiamide content (X ₁ ) expressed in mass percentage is calculated according to formula (1):

In the formula: V ₁ -the volume of the standard titration solution of hydrochloric acid consumed by the sample, mL;

V ₀ —Blank test consumes the volume of hydrochloric acid standard titration solution, mL;

c—The actual concentration of hydrochloric acid standard titration solution, mol/L;

m—the mass of the sample, g;

0.
02102—The mass of dicyandiamide expressed in grams equivalent to 1.
00ml hydrochloric acid standard titration solution [c(HCI)=1.
000mol/L]
.

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6 Tolerance

Take the arithmetic mean of the two parallel determination results as the determination result
.
The difference between the two parallel determination results shall not exceed 0.
2%
.

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2 Determination of heating loss

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2.
1 Analysis steps

Weigh 5g sample and dry it at 105℃～110℃ for 3h
.
Others shall be carried out in accordance with the provisions of GB/T6284
.

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2.
2 Allowable difference

Take the arithmetic mean of the two parallel determination results as the determination result
.
The difference between the two parallel determination results shall not be more than 0.
05%
.

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3 Determination of Ash

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3.
1 Analysis steps

Weigh 5g of sample (accurate to 0.
01g), add 1mL of sulfuric acid , and burn at (850±25)℃.
Others shall be carried out in accordance with the provisions of "solid samples" in GB/T9741
.

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3.
2 Allowable difference

Take the arithmetic mean of the two parallel determination results as the determination result
.
The difference between the two parallel determination results shall not exceed 0.
01%
.

Related Links: Industrial Dicyandiamide (1)