HG/T 2566-2014Barium hydroxide for industrial use (English PDF)

5.1 General Provisions

Unless otherwise specified, the reagents and water used in this Standard refer to analytical grade reagents and Grade 3 water as specified in GB/T 6682-2008.Unless otherwise specified, the standard volumetric solutions, standard solutions for impurity, and reagent solutions used in the tests shall be prepared in accordance with the provisions of HG/T 3696.1, HG/T 3696.2, and HG/T 3696.3.

5.2 Visual Inspection

The appearance shall be determined by visual inspection under natural light.

5.3 Determination of Main Content

5.3.1 Summary of method

Dissolve the specimen in an appropriate amount of water, and titrate with a standard volumetric solution of hydrochloric acid using phenolphthalein as the indicator. Calculate the barium hydroxide content based on the volume of hydrochloric acid consumed.

5.3.2 Reagents

5.3.2.1 Standard volumetric solution of hydrochloric acid. c(HCl)~1 mol/L.

5.3.2.2 Phenolphthalein indicator solution. 10 g/L.

5.3.2.3 Carbon dioxide-free water.

5.3.3 Analytical procedures

Weigh approximately 4 g of the specimen to the nearest 0.0002 g. Place it in a 250 mL conical flask and add 50 mL of carbon dioxide-free water to dissolve. Add 2 drops of phenolphthalein indicator solution, and immediately titrate with a standard volumetric solution of hydrochloric acid until the red color disappears, marking the endpoint.

Retain this solution; this is test solution A, used for the determination of barium carbonate content.

5.3.4 Result calculation

The main content is expressed as the mass fraction (w1) of barium hydroxide octahydrate [Ba(OH)2·8H2O] and calculated according to Formula (1).

Where.

V -- The numerical value of the volume of standard volumetric solution of hydrochloric acid consumed for the titration test solution, in milliliters (mL);

c -- The exact concentration value of the standard volumetric solution of hydrochloric acid, in moles per liter (mol/L);

m -- The numerical value of the mass of the specimen, in grams (g);

M -- The numerical value of the molar mass of barium hydroxide octahydrate [1/2Ba(OH)2·8H2O], in grams per mole (g/mol) (M=157.7).

The arithmetic mean of the results of parallel determinations is taken as the determination result.

The absolute difference between the results of two parallel determinations is not greater than 0.3%.

5.4 Determination of Barium Carbonate Content

5.4.1 Summary of method

Titrate with a standard volumetric solution of hydrochloric acid using bromophenol blue as the indicator solution, and calculate the barium carbonate content based on the volume of standard volumetric solution of hydrochloric acid consumed.

5.4.2 Reagents

5.4.2.1 Standard volumetric solution of hydrochloric acid. c(HCl)~0.2 mol/L.

5.4.2.2 Bromophenol blue indicator solution. 0.4 g/L.

5.4.3 Instruments

Micro-burette. with a graduation value of 0.02 mL.

5.4.4 Analytical procedures

Add 10 ~ 12 drops of bromophenol blue indicator solution to test solution A (see 5.3.3). Using a micro-burette, titrate with a standard volumetric solution of hydrochloric acid until the solution changes from blue-violet to yellow and the color remains stable for 30 s; this marks the endpoint.

5.4.5 Result calculation

The barium carbonate content is expressed as the mass fraction (w2) of barium carbonate (BaCO3) and calculated according to Formula (2).

Where.

V -- The numerical value of the volume of standard volumetric solution of hydrochloric acid consumed for the titration test solution, in milliliters (mL);

c -- The exact concentration value of the standard volumetric solution of hydrochloric acid, in moles per liter (mol/L);

m -- The numerical value of the mass of the test portion (see 5.3.3), in grams (g);

M -- The numerical value of the molar mass of barium carbonate (1/2BaCO3), in grams per mole (g/mol) (M=98.65).

The arithmetic mean of the results of parallel determinations is taken as the determination result.

The absolute difference between the results of two parallel determinations is not greater than 0.3%.

5.5 Determination of Chloride Content

5.5.1 Summary of method

Chloride in the sample reacts with the added silver nitrate solution to form turbidity; the chloride content is assessed based on the degree of turbidity.

5.5.2 Reagents

5.5.2.1 Nitric acid solution. 1+2.

5.5.2.2 Silver nitrate solution. 17 g/L.

5.5.2.3 Dextrin solution. 20 g/L.

5.5.2.4 Chloride standard solution. 1 mL of solution contains 0.010 mg of chloride (Cl).

Pipette 1.00 mL of the chloride standard solution (prepared according to HG/T 3696.2) into a 100 mL volumetric flask, dilute to the mark with water, and mix well (prepare this solution immediately before use).

5.5.3 Analytical procedures

5.5.3.1 Preparation of test solution

Weigh 1.00 g±0.01 g of the specimen into a 100 mL beaker; add 25 mL of water and 3 mL of nitric acid solution to dissolve it. Quantitatively transfer the solution to a 100 mL volumetric flask and dilute to the mark with water. Mix well.

5.5.3.2 Determination

Filter the test solution through dry filter paper and discard the first 20 mL of the filtrate. Pipette 10 mL of the filtrate into a 50 mL colorimetric tube; add 5 mL of nitric acid solution, 0.2 mL of dextrin solution, and 1 mL of silver nitrate solution; dilute to the mark with water and mix well.

Allow to stand in the dark for 15 min; the turbidity shall not exceed that of the standard turbidity solution.

The standard turbidity solution is prepared by pipetting 3 mL of the chloride standard solution into a 50 mL colorimetric tube and subjecting it to the same treatment as the test solution.

5.6 Determination of Iron Content

5.6.1 Summary of method

Same as Clause 3 of GB/T 3049-2006.

5.6.2 Reagents

Same as Clause 4 of GB/T 3049-2006.

5.6.3 Instruments

Same as Clause 5 of GB/T 3049-2006.

5.6.4 Analytical procedures

5.6.4.1 Plotting of standard curve

In accordance with the provisions of Section 6.3 of GB/T 3049-2006, plot a standard curve using a 5 cm cuvette and the corresponding amounts of iron standard solution.

5.6.4.2 Preparation of test solution

Weigh approximately 4 g of the specimen to the nearest 0.0002 g. Place it in a 100 mL beaker, add 15 mL of water, 20 mL of hydrochloric acid solution (1+1), and 5 drops of nitric acid, then heat to boiling for 5 min. After cooling, filter the mixture into a 100 mL volumetric flask, dilute to the mark with water, and mix well.

5.6.4.3 Preparation of blank test solution

Except that no specimen is added, the quantities of reagents added are identical to those used in the preparation of the test solution, and the blank undergoes the same treatment concurrently with the specimen.

5.6.4.4 Determination

Pipette 25 mL of the test solution and an equal volume of the blank test solution into separate 100 mL volumetric flasks. Proceed according to the procedure specified in Section 6.4 of GB/T 3049-2006, starting from the step. "if necessary, add water to approximately 60 mL...".

Determine the mass of iron from the standard curve based on the absorbances of the test solution and the blank test solution.

5.6.5 Result calculation

The iron content is expressed as the mass fraction (w3) of iron (Fe) and calculated according to Formula (3).

Where.

m1 -- The numerical value of the mass of iron in the test solution, determined from the standard curve, in milligrams (mg);