Detection of elemental parameters in salt/food

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This standard specifies the detection methods for sodium chloride, lead, total arsenic, cadmium, total mercury, barium, potassium chloride, potassium ferrocyanide, and iodine in table salt

This standard is applicable to the determination of salt indicators

2. Determination of sodium chloride

2.1 Determination of moisture

Follow the direct drying method in GB 5009.3 and set the drying temperature to 140 ℃± 2 ℃. Drying until the difference in mass between the two times does not exceed 5mg is considered constant weight

2.2 Determination of chloride ions

Principle of 2.2.1

After the sample is dissolved, potassium chromate is used as an indicator and titrated with silver nitrate standard titration solution to determine the content of chloride ions.

2.2.2 Reagents and Materials

Unless otherwise specified, all reagents used in this method are analytical pure, and the water is Grade III water as specified in GB/T 6682.

2.2.2.1 Reagents

2.2.2.1.1 Silver nitrate

2.2.2.1.2 Potassium chromate

2.2.2.2 Preparation of reagents

2.2.2.2.1 Silver nitrate standard titration solution (0.1mol/L)

2.2.2.2.2 Potassium chromate indicator: Weigh 10g of potassium chromate and dissolve it in 100mL of water, stir and add silver nitrate solution dropwise until a reddish brown precipitate appears, and filter

2.2.3 Instruments and Equipment

2.2.3.1 Balance: Sensitivity 0.1mg

2.2.3.2 Water bath pot

2.2.4 Analysis Steps

2.2.4.1 Sample Treatment

Weigh 25g (accurate to 0.001g) of crushed sample into a 400mL beaker, add about 200mL of water, heat, and stir with a glass rod until fully dissolved.

. After cooling, transfer to a 500mL volumetric flask, add water to volume, shake a spoon, and filter if necessary. Take 25.00mL of the sample solution into a 250mL volumetric flask, bring to volume with water, and mix well

2.2.4.2 Determination

Take 25.00mL of diluted sample solution (2.2.4.1) into a 150mL conical flask, add water to 50mL, add 4 drops of potassium chromate indicator (2.2.2.2.2), stir and titrate with silver nitrate standard titration solution (2.2.2.2.1) until a stable orange red color appears in the suspension as the endpoint. Simultaneously conduct a blank test

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