GB 6857-1986pH primary reagent -- Potassium hydrogen phthalate (English PDF)

5.1 Warning

Reagents used in this test method are toxic or corrosive, some of the testing process can lead to dangerous situations, the operator should take Appropriate safety and health practices.

5.2 General Provisions

Unless specified otherwise in this chapter, the use of standard titration solution, standard solution, preparations and products, according to GB/T 601, GB/T 602, Regulations preparation, test water should be consistent with GB/T 6682 specifications in three water samples according to precise weighing 0.01g, the use of GB/T 603's Solution "%" are represented by the mass fraction.

According to the provisions of GB 6851 was measured using a palladium electrode dihydrotestosterone. Potassium hydrogen phthalate pH of the solution (S) I value (0.05mol/kg, 25 °C) certificate by the standard substance used to look up.

5.4 Content

Determined according to the provisions of GB 1257-2007 5.3.

5.5 Clarity test

Clarity Standard No. 2 Weigh 7.5g sample, add 100mL water dissolved by heating, turbidity shall not exceed HG/T 3484 stipulated.

5.6 Water insoluble matter

Weigh 40g sample, add 400mL of water, heated and dissolved in the water bath for 1h, the determination according to the provisions GB/T 9738's.

5.7 Loss on drying

Weigh 5g samples, accurate to 0.0001g, has been placed at 105 °C ~ 110 °C constant weighing bottle, at 105 °C ~ 110 °C of Electric oven dried to constant weight. Constant retention samples for determination.

Loss on drying mass fraction of 1, the value in the "%" means, according to equation (1).

100 (1)

Where.

5.8 Chloride

5g samples were weighed, dissolved in 30mL hot water, cooling, 10mL of nitric acid, filtered and diluted to 50mL. Take 10mL, press the provisions of GB/T 9729 Determination. The turbidity of the solution was not greater than the standard turbidity solution.

Standard preparation turbid solution is to take the ratio of 0.02mg containing chloride (Cl) standard solution was diluted to 10mL, and at the same time with the same volume of test solution Sample processing.

5.9 Sulfur compounds

Weigh 0.5g sample was placed in a platinum crucible, add anhydrous sodium carbonate 0.2g, mixing, add 2mL water wet, evaporated on a water bath heated to completely carbonized, gradually warmed up to 700 °C and burning to white. As no white residue, add a small amount of cooling water wet, evaporated on a water bath, then blanch burn. Repeat this operation until the residue was completely white, cool, add water, 5mL dissolved (filtered if necessary) with hydrochloric acid (20%) and, dilute Diluted to 10mL, plus 5mL "ethanol (95%)", 0.5mL hydrochloric acid solution (20%), constantly shaking dropping 3mL barium chloride solution (250g/L), diluted to 25mL, shake, place 10min. The turbidity of the solution was not greater than the standard turbidity solution.

Standard preparation turbid solution is to take the ratio of 0.03mg containing sulfate (SO4) standard solution, and treated in the same sample at the same time.

5.10 Ammonium

Weigh 1g sample was determined according to the provisions of GB/T 9732's. The yellow solution can not be deeper than the standard colorimetric solution.

Preparation of the standard developing solution containing 0.03mg ratio is taken of ammonium (NH4) standard solution, the same treatment simultaneously with the sample.

Sodium 5.11

Determined according to the provisions of GB/T 9723-2007 of.

5.11.1 Instrument Conditions

Source. sodium hollow cathode lamp;

Wavelength. 589.0nm;

Flame. acetylene - air.

5.11.2 Determination

Weigh 1g sample was dissolved in water and diluted to 100mL. Take 20mL, a total of four. According to the provisions of GB/T 9723-2007 in 7.2.2 Measurement results calculated according to the provisions of 7.2.3.

5.12 Iron

Weigh 1g sample was dissolved in 15mL water, the solution pH is adjusted with hydrochloric acid solution (15%) to 2, according to GB/T 9739 regulations Fixed determination. The red solution should not be deeper than the standard colorimetric solution.

Preparation of the standard solution is to take the colorimetric containing 0.005mg of iron (Fe) standard solution, the same treatment simultaneously with the sample.

5.13 Heavy Metal

4g weighed sample was dissolved in 40mL water, and cooled. Take 30mL, 0.2mL added acetic acid (30%) and 10mL freshly prepared saturated Hydrogen sulfide and water, shake, place 10min. The solution was dark can not be deeper than the standard colorimetric solution.

Standard Preparation of color solution ratio is to take the remaining 10mL sample solution and standard solution containing 0.01mg of lead (Pb), diluted to 30mL, simultaneously with the same volume of the same treated sample solution.