Industrial dicyandiamide (3)

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The sample is titrated with a standard titration solution of disodium ethylenediaminetetraacetic acid (EDTA) in an alkaline medium

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Dilute with standard titration solution c(EDTA)=0.

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Mix 1.

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Weigh 5g sample (accurate to 0.

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The calcium (Ca) content (X ₂ ) expressed in mass percentage is calculated according to formula (2):

In the formula: V ₁ -the volume of the standard titration solution of disodium edetate consumed by the sample, ml;

V ₂ —Blank test consumes the volume of disodium ethylenediaminetetraacetic acid standard titration solution, mL;

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

m—the mass of the sample, g;

0.

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5 Allowance

Take the arithmetic mean of the two parallel determination results as the determination result
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The difference between the two parallel determination results shall not exceed 0.
003%
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5 Impurity precipitation test 4.
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1 Method summary

Nitrogen-containing impurities in the sample react with picric acid to produce yellow flocculent precipitate.
The precipitate produced by the sample solution is compared with the standard comparison solution
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2 Reagents and materials

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1 Picric acid solution: 15g/L
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2 Melamine standard solution: 1mg (H ₂ CN ₂ ) ₃ per milliliter
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Weigh 0.
100g of melamine , dissolve it in water, transfer it into a 100ml volumetric flask, and dilute to the mark
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3 Analysis steps

Weigh 1g sample (accurate to 0.
01g), place it in a 250mL beaker, add 50mL of water to dissolve it by heating, cool to room temperature, add 30mL picric acid solution, stir for 1min, place it in a 100mL colorimetric tube, and place it for 30min
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The obvious degree of precipitation of the sample solution shall not be higher than that of the standard comparison solution
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Take 2mL of melamine standard solution for standard comparison solution , and treat it with the sample at the same time (no need to dissolve by heat)
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5 Inspection rules

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1 The quality of industrial dicyandiamide is inspected by the quality inspection department of the manufacturer in accordance with the provisions of this standard
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The manufacturer shall ensure that the manufactured products meet the requirements of this standard
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The user has the right to check and accept the products received in accordance with the provisions of this standard
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Each batch of products should be accompanied by a quality certificate in a certain format, which includes: product name, grade, manufacturer name, batch number or production date, batch size and this standard number
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2 Take products of the same quality as a batch, and each batch of products shall not exceed 5t
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3 Determine the number of sampling units according to 6.
6 of GB/T6678-1986
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Sampling should meet the requirements of Chapter 2 in GB/T6679-1986
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When sampling, use a sampling probe to diagonally insert from the top to 3/4 of the depth of the material layer to sample
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Quickly mix the collected samples uniformly, divide them by quarters to no less than 400g, and divide them into two clean and dry ground-mouth bottles
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Affix the label to indicate: the name of the manufacturer, the name of the sample, the batch number, the date of sampling, and the name of the sampler
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One bottle is for inspection, and the other bottle is kept for 3 months for future reference
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4 The test result is judged according to GB/T1250 rounding value comparison method
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If one indicator of the inspection result does not meet the requirements of this standard, samples should be taken from twice the number of packaging units for re-inspection.
If there is still one indicator that does not meet the requirements of this standard, the batch of products will be considered unqualified
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6 Marking, packaging, transportation and storage

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1 The packaging of industrial dicyandiamide should have a firm and clear mark, including: product name, trademark, grade, manufacturer name and address, batch number or production date, net content, and the number of this standard
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2 Industrial dicyandiamide is packaged in a woven bag lined with a plastic bag or a paper bag made of five layers of kraft paper
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The bag mouth is tightly sealed, and no leakage is allowed
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The net content of each bag is (25±0.
2)kg
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3 The industrial dicyandiamide should be protected from rain and moisture during transportation, and it should be handled and handled with care during loading and unloading
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4 Industrial dicyandiamide should be stored in a dry, ventilated and cool place
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