Trichloroisocyanuric acid (two)

4 Test method

The reagents and water used in this standard, unless other requirements are specified, are analytical reagents and grade 3 water specified in GB/T6682

4.

4.

The sample reacts with potassium iodide in an acidic medium to precipitate iodine, which is titrated with sodium thiosulfate standard titration solution using starch as an indicator to calculate the available chlorine content

4.

a) Potassium iodide ,

b) Sulfuric acid solution: 1+5

c) Sodium thiosulfate standard titration solution: c(Na ₂ S ₂ O ₃ )=0.

d) Starch indicator solution: 5g/L

4.

General laboratory equipment and magnetic stirrer,

4.

Weigh about 0.

4.

The content X of available chlorine (calculated as CI) expressed in mass percentage is calculated according to formula (1):

Where:

V—volume of sodium standard titration solution that consumes sulfur in titration, mL;

C—The actual concentration of sodium thiosulfate standard titration solution, mol/L;

m—the mass of the sample, g;

0.

4.

Take the arithmetic mean of the two parallel determination results as the determination result

4.

4.
2.
1 Method summary

The sample was dried at a constant temperature of (104±1)°C for 2h and determined by gravimetric method
.

4.
2.
2 Apparatus

a) Weighing bottle: inner diameter 50mm, height 30mm
.

b) Oven: Temperature control accuracy: ±1℃
.

c) Desiccator: It contains suitable desiccant
.

4.
2.
3 Analysis steps

Use a weighing bottle that has been dried to a constant weight at (104±1)℃ to weigh about 2g of the sample (accurate to 0.
0002g), put it in the oven, open the cap, and bake at (104±1)℃ Dry for 2 hours, close the bottle cap, take out the weighing bottle, cool to room temperature (not less than 30mnin) in a desiccator, and weigh
.

Note: If the oven temperature exceeds 105°C, trichloroisocyanuric acid may undergo sublimation
.

4.
2.
4 Expression of analysis results

The moisture X ₂ expressed in mass percentage is calculated according to formula (2):

In the formula: m _o — weigh the mass of the sample, g;

m ₁ ——weight of weighing bottle and sample before drying, g;

m ₂ ——The mass of the weighing bottle and sample after drying, g
.

4.
2.
5 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 be more than 0.
05%
.

4.
3 Determination of pH

4.
3.
1 Instruments and equipment

a) Acidity meter: equipped with glass measuring electrode and saturated calomel reference electrode or composite electrode, the graduation value is 0.
02pH unit
.

b) Magnetic stirrer
.

4.
3.
2 Analysis steps

Weigh 1g of the sample (accurate to 0.
1g), place it in a 100mnL beaker, add 100mL carbon dioxide-free water, stir on a magnetic stirrer until completely dissolved, and measure the pH value with an acid meter
.

4.
3.
3 Tolerance

Take the arithmetic average of the two parallel determination results as the determination result, and the difference between the two parallel determination results shall not exceed 0.
1 pH unit
.

Related links: Trichloroisocyanuric acid (1)