Oxalic acid for industrial use (4)

6.

According to the provisions of GB/T3049-2006

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Hydrochloric acid

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Weigh an appropriate amount of sample to make the iron content of the sample within (0.

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The mass fraction of iron (calculated as Fe) w ₄ , the value is expressed in %, calculated according to formula (4):

Where:

X—The value of the iron mass obtained from the working curve, in milligrams (mg);

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

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

When the mass fraction of iron is less than 0.

When the mass fraction of iron is (0.

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In an acidic solution, chloride and silver nitrate produce a white precipitate of silver chloride , which is turbidity with the standard turbidity solution

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6.
2.
2 Silver nitrate solution: 17g/L;

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6.
2.
3 Chloride (CI) standard solution: 0.
1mg/mL
.

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6.
3 Analysis steps

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6.
3.
1 Preparation of chloride standard turbidity solution

According to different levels of chloride content index values, draw chloride standard solution (0, 05, 0.
20, 0.
40, 1.
00) mL into a 50 mL colorimetric tube, then add 5 mL of nitric acid solution, and add water to 25 mL
.
This solution is used as the standard turbidity solution of chloride
.

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6.
3.
2 Determination

Weigh 1g of the sample, accurate to 0.
001g, place it in a 50mL colorimetric tube, dissolve it with a small amount of water, then add 5mL of nitric acid solution, and add water to 25mL
.
This solution is used as the sample solution,

Add 1 mL of silver nitrate solution to the colorimetric tube containing the sample solution and the chloride standard turbidity solution, mix well, and leave for 15 minutes to compare the sample solution and the chloride standard turbidity solution axially
.
The turbidity of the sample solution shall not be deeper than the turbidity of the chloride standard turbidity solution
.

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7 Determination of calcium content

Flame atomic absorption spectrometry is carried out in accordance with the provisions of 6.
5.
1
.

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7.
1 Instrument operating conditions

Calcium hollow cathode lamp, wavelength 422.
7nm, slit width 0.
4nm, lamp current 2mA
.

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7.
2 Analysis steps

Drawing the working curve: Take calcium standard solution (0, 1.
0, 2.
0, 3.
0, 4.
0, 5.
0) mL, put them in 6 100 mL volumetric flasks, add 5 mL hydrochloric acid, dilute to the mark with water, and shake well
.
As a calcium standard working solution
.
The solution contains calcium (0,1,2,3,4,5)ug per milliliter
.
The following measurements are carried out in accordance with the provisions of 6.
5.
1.
5
.

7 Inspection rules

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1 All items specified in Table 1 in the requirements of Chapter 3 are ex-factory inspection items, and ex-factory inspection shall be carried out once per batch
.

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2 The quality of each batch of oxalic acid products for industrial use shall not exceed 20t
.

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3 The number of oxalic acid sampling units for industrial use shall be determined in accordance with 7.
6.
1 of GB/T667-2003
.

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4 The sampling method of oxalic acid for industrial use shall be carried out in accordance with the provisions of GB/T6679-2003, the sampling amount shall not be less than 500g, and the mixture shall be installed in two clean, dry, ground stoppered Guangshan bottles
.
Affix the label to indicate the product name, batch number, product model, sampling date, sampling location, and sampler’s name
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One bottle is for inspection and the other bottle is kept for samples.
Domestic products are stored for 3 months, and samples for export products are stored for 6 months
.

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5 Oxalic acid for industrial use shall be inspected by the quality supervision and inspection department of the manufacturer
.
The manufacturer shall ensure that the manufactured products meet the requirements of this standard, and each batch of manufactured products shall be accompanied by a quality certificate in a certain format, including: manufacturer name, product name, production date or batch number, product model, product grade and this standard number and so on
.

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6 The judgment of the inspection result shall be carried out according to the comparison method of rounding value in GB/T1250
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If one of the inspection results does not meet the requirements of this standard, samples should be taken from twice the volume of the packaging unit for re-inspection.
Even if only one index does not meet the requirements of this standard, the entire batch of products should be re-inspected.
Disqualification treatment
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8 Marking, packaging, transportation and storage

8.
1 Industrial oxalic acid should be firmly on the packaging container mark, indicating the product name, manufacturer plant name and address, trademark, production date or production lot number, product type, quality grade, net content and standard number and so on
.

8.
2 For industrial packaging of oxalic acid, use a plastic woven bag lined with plastic film that meets the requirements of GB/T8947, or customize packaging according to wide-ranging needs
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The net weight of each package is 25kg, or it can be packaged according to user requirements
.

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3 When transporting oxalic acid for industrial use, it should be packed in a clean and dry transportation tool.
When transporting, be careful to handle it carefully to prevent damage to the packaging bag
.

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4 The temperature of industrial oxalic acid during storage and transportation should not be higher than 40℃, and it should be protected from moisture, rain, and separated from alkaline substances to prevent contact with food
.
Avoid direct contact with skin during handling
.