How to identify sodium dihydrogen phosphate is qualified?

Identification of sodium dihydrogen phosphate is qualified

The acidity of sodium dihydrogen phosphate is 2.0g of this product, dissolved in 40ml of water, and determined according to law. The pH value should be 4.1 ~ 4.5.

The chloride takes 0.50g of the product and is checked according to law. Compared with the control solution made of 5.0ml of standard sodium chloride solution, it cannot be thicker ( 0.01% ).

The sulfate is 1.0g of this product, which shall be checked according to law and shall not be thicker ( 0.05% ) than the control solution made of 5.0ml of standard potassium sulfate solution.

Loss on drying takes the product and dries it at 60 ℃ for 2 hours, then at 105 ℃ to constant weight. The weight loss should be 10.0% ~ 15.0%.

Take 0.50g of aluminum salt, add appropriate amount of water to dissolve it, add 5 ml of acetic acid-ammonium acetate buffer ( pH 4.5 ), add water to 25ml, add 1ml of 0.1% aluminum reagent solution, shake well, if it turns red, add 1.76 g of aluminum potassium sulfate [ ALK ( SO ) 12HO ] with standard aluminum solution [ Precision Weighing ], place in a 1000ml volumetric flask, add appropriate amount of water to dissolve and dilute to scale, shake well; Before use, take a precise measurement of 10ml, place it in a 100ml volumetric flask, add water to dilute it to the scale, shake well, and compare the control solution made of 5.0 ml of Al equivalent to 10μg per 1ml, and it shall not be deeper ( 0.01% ).

Calcium salt takes 0.50g of the product, adds appropriate amount of water to dissolve it, adds 1ml of ammonium oxalate test solution, and after standing for 1 minute, adds 2ml of dilute acetic acid and 5ml of ethanol, adds water to 25ml, and shakes well. If it is cloudy, it is mixed with standard calcium solution ( weigh precisely 0.125g of calcium carbonate dried at 105 ℃ to constant weight, place it in a 500ml volumetric flask, add 5ml of water and 0.5ml of hydrochloric acid to dissolve it, dilute it to scale with water, and shake well; Before use, take a precise measurement of 10ml, place it in a 100ml volumetric flask, add water to dilute it to the scale, shake well. Compared with the control solution made of 5.0 ml of 1ml equivalent to 10μg of CA ), it shall not be thicker ( 0.01% ).

Take 1.0g of heavy metal from this product, add 20ml of water to dissolve it, add 2 ml of acetate buffer ( pH 3.5 ) and appropriate amount of water to make it into 25ml, and check according to law, the content of heavy metal shall not exceed 10 parts per million.

Arsenic salt takes 0.4g of the product, adds 23ml of water to dissolve the product, adds 5ml of hydrochloric acid, and checks according to law, which shall conform to the regulations ( 0.0005% ).

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