GB 6856-1986pH primary reagent -- Sodium tetraborate decahydrate (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 platinum electrode dihydrotestosterone. pH of sodium tetraborate (S) I (0.01mol/kg, 25 °C) by the the reference material certificates Richard.

5.4 Content

Weigh 2.8g sample, accurate to 0.0001g, dissolved in 100mL of water, plus 20.00mL hydrochloric acid standard titration solution [Ba (HCl) = 1mol/L], add 1 drop of methyl red indicator solution (1g/L), titrated with standard sodium hydroxide solution [Ba (NaOH) = 1mol/L] titrated to yellow Color, when sodium hydroxide standard titration solution in an amount not count. Add 11g of mannitol, dissolved, 2 drops of phenolphthalein indicator solution (10g/L), hydrogen Sodium hydroxide standard titration solution [Ba (NaOH) = 1mol/L] titrated to a solution pink.

The mass fraction of sodium tetraborate and its value is "%" means, according to equation (1).

100 (1)

Where.

Value Vp --- sodium hydroxide standard titration solution volume in milliliters (mL);

Accurate Ba --- sodium hydroxide standard titration solution concentration value in units of moles per liter (mol/L);

--- The M sodium tetraborate numerical molar mass in grams per mole (g/mol) [M (14 Na2B4O7

· 10H2O) = 95.34];

5.5 Clarity test

7g weighed sample was dissolved in 7mL hydrochloric acid solution (20%) and 100mL hot water turbidity is not greater than HG/T 3484 stipulated no. 2 standard clarity.

5.6 Hydrochloric acid insoluble matter

Weigh 50g sample was dissolved in 500mL water and 50mL hydrochloric acid solution (20%), on the water bath for 1h, has been used in 105 °C ± 2 °C constant No. 4 glass filter crucible was filtered, the filter residue washed with hot water until no chlorine ions react lotion, dried in an electric oven at 105 °C ± 2 °C in Dry to constant weight. Residue mass not greater than 1.0mg.

5.7 Chloride

Weigh 1g sample was dissolved in an appropriate amount of hot water, cooling, 1mL solution of nitric acid (25%), diluted to 20mL, press GB/T 9729 Determination of the provisions. The turbidity of the solution was not greater than the standard turbidity solution.

Standard preparation turbid solution is to take the ratio of 0.005mg containing chloride (Cl) standard solution was diluted to 20mL, at the same time with the same volume of test solution the same treatment.

5.8 Sulfate

Weigh 0.5g sample was dissolved in 20mL water, cooled, washed with hydrochloric acid solution (20%), add 0.5mL hydrochloric acid solution, and (20%) acid After the technology, according to the provisions of GB/T 9728 Determination. The turbidity of the solution was not greater than the standard turbidity solution.

Turbidity standard solution was prepared containing 0.025mg ratio is taken sulfate (SO4) standard solution was diluted to 20mL, and during and after the test solution While the same treatment.

5.9 Phosphate

Weigh 0.5g sample was dissolved in an appropriate amount of hot water, add 2 drops of saturated 2,4-dinitrophenol indicator solution, a solution of nitric acid solution (13%) to yellow Just disappeared, after diluted to 10mL, according to the provisions of GB/T 9727 Determination. The organic layer was blue can not be deeper than the standard colorimetric solution.

Preparation of the standard developing solution containing 0.005mg is to take the ratio of phosphate (PO4) standard solution, the same treatment simultaneously with the sample.

5.10 Carbonate

2g sample was weighed, dissolved in 40mL of water was added slowly 5mL hydrochloric acid solution (20%), no bubbles.

5.11 Magnesium and calcium

10g samples were weighed, dissolved in 100mL hot water, cooling, 2mL solution of sodium sulfide (20g/L), 1mL ethylenediaminetetraacetic acid magnesium solution Solution [Ba (EDTA-Mg) = 0.01mol/L] and 10mL of ammonia - ammonium chloride buffer solution A (pH~10), add 2 drops of chrome black T indicator solution, with Disodium edetate standard titration solution [Ba (EDTA) = 0.02mol/L] titration to the solution from purple to pure blue. Ethylenediamine Disodium standard titration solution [Ba (EDTA) = 0.02mol/L] in an amount not more than 0.62mL.

5.12 K

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

5.12.1 Instrument Conditions

Source. Potassium hollow cathode lamp;

Wavelength. 766.5. nm;

Flame. acetylene - air.

5.12.2 Determination

5g samples were weighed, dissolved in an appropriate amount of hot water, cooled and diluted to 50mL. Take 2mL, a total of four. According to GB/T 9723-2007 in 7.2.2 predetermined measurement results calculated according to the provisions of 7.2.3.

5.13 Iron

2g sample was weighed, dissolved in an appropriate amount of hot water, was cooled, was diluted to 15mL, after the solution pH was adjusted with hydrochloric acid solution (15%) 2, by the provisions of GB/T 9739 Determination. The red solution should not be deeper than the standard colorimetric solution.

Preparation of the standard developing solution containing 0.002mg is to take the ratio of iron (Fe) standard solution was diluted to 15mL, at the same time with the same volume of sample solution the same treatment.

5.14 Arsenic

Weigh 1g sample was dissolved in an appropriate amount of water and sulfuric acid solution (20%), diluted to 70mL. According to GB/T 610-2008 4.1 Determination of the provisions. Mercuric bromide paper that was brown not be deeper than the standard colorimetric test strips.

Standard color strip ratio is prepared to take 0.0001mg containing arsenic (As) standard solution and the sample solution and at the same time after the same treatment.

Book GB 6856-2008

5.15 Heavy Metal

4g weighed sample was dissolved in an appropriate amount of hot water, treated with acetic acid (glacial acetic acid), diluted to 40mL, cooling. Take 30mL, add 0.2mL B Acid (30%) of freshly prepared saturated hydrogen sulfide and water 10mL, 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.