GB 28653-2012Ammonium fluoride for industrial use (English PDF)

5.1 Safety Tips

Ammonium fluoride this test method the samples taken toxic, deliquescent and strongly acidic aqueous solution in the air, part of the test used Also corrosive agent, an operator should be careful to avoid contact with the skin; the skin, such as contact immediately wash with water, shall immediately severe Medical treatment.

5.2 General Provisions

This standard reagent and water, in the absence of other requirements specified, are by analytical reagent and GB/T 6682-2008 specified Tertiary water used in the test standard titration solution, impurity standard solution, formulations and products, in the absence of other requirements specified, are by HG/T 3696.1, HG/T 3696.2, preparing a predetermined HG/T 3696.3 is.

5.3 Visual inspection

In natural light, white plastic plate is placed is determined by visual appearance.

5.4 Determination of the content of ammonium fluoride

5.4.1 Method summary

Samples dissolved in water, adding ammonium ions react with formaldehyde, hexamethylenetetramine generate and release an acid to phenolphthalein as an indicator, with sodium hydroxide Standard Solution titration, subtracting the result of free acids and fluoro-silicate content, obtain the content of ammonium fluoride.

5.4.2 Reagents

5.4.2.1 neutral formalin solution. 11. Mixed formaldehyde and other volumes of water, add 2 drops of phenolphthalein indicator, titrate with standard sodium hydroxide solution Titrated to a pale pink.

5.4.2.2 sodium hydroxide standard titration solution. c (NaOH) ~0.5mol/L.

5.4.2.3 phenolphthalein indicator solution. 10g/L.

5.4.3 Analysis of step

Weigh about 0.5g sample, accurate to 0.0002g, placed in a plastic cup, add 20mL water soluble, neutral formalin solution was added 40mL shake Uniform, placed 30min. Add 2 drops of phenolphthalein indicator solution, the solution was pink titrated with standard sodium hydroxide solution was titrated to, and does not fade holding 30s Color is the end.

5.4.4 Calculation results

Ammonium fluoride ammonium fluoride content (of NH4F) w1 mass fraction basis, calculated according to formula (1).

(V/1000) cM

m × 100% -1.851w2-0.4158w3 (1) where.

Sodium hydroxide standard titration solution volume V --- titration test solution consumed value in milliliters (mL);

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

Value m --- mass of the sample in grams (G);

--- numerical molar mass M ammonium fluoride (NH4F), in units of grams per mole (g/mol) (M = 37.04);

--- value w2 of the free acid content of 5.5 determined;

W3 --- fluoro silicate content by determination of the value 5.6;

--- 1.851 in terms of coefficient of hydrogen fluoride ammonium fluoride;

0.4158 --- ammonium fluorosilicate factor in terms of ammonium fluoride.

Parallel to the arithmetic average of the measurement results of the measurement result, the absolute difference determination results parallel to not more than 0.3%.

Determination of free acid content of 5.5

5.5.1 Method summary

Samples were dissolved in water, Bromocresol purple as an indicator, titrated with standard sodium hydroxide solution.

5.5.2 Instruments and equipment

Microburette. reference value 0.02mL.

5.5.3 Reagents and materials

5.5.3.1 sodium hydroxide standard titration solution. c (NaOH) ~0.1mol/L.

5.5.3.2 bromocresol purple indicator solution. 1g/L. Weigh 0.10g bromocresol purple, was dissolved in ethanol 100mL95%.

5.5.3.3 carbon dioxide-free water.

5.5.4 Analysis of step

Weigh about 1g sample, accurate to 0.001 g of, placed in a plastic cup, add 50mL water without carbon dioxide dissolved, 2 drops of bromocresol Purple indicator solution, titration with a sodium hydroxide standard solution was titrated to the end point of the solution was purple.

5.5.5 Calculation results

The free acid content of hydrogen fluoride (HF) w2 mass fraction basis, calculated according to formula (2).

(V/1000) cM

m × 100%

Where.

Sodium hydroxide standard titration solution volume V --- titration test solution consumed value in milliliters (mL);

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

Value m --- mass of the sample in grams (G);

--- numerical molar mass M hydrogen fluoride (HF), in units of grams per mole (g/mol) (M = 20.01).

Parallel to the arithmetic average of the measurement results of the measurement result, the absolute difference determination results parallel not greater than 0.15%.

5.6 Determination of the content of fluorosilicate

5.6.1 Method summary

Sample was dissolved in water, adding boric acid to eliminate interference with fluoride ions complexed fluorine. Quantitative reaction with ammonium molybdate added silicic acid, silicon-molybdenum generated Heteropolyacids (Si - Mo), in the presence of oxalic acid was added stannous chloride reduction of the Si - Mo is molybdenum blue silicon count measured by a spectrophotometer.

5.6.2 Reagents

5.6.2.1 boric acid. 40g/L.

5.6.2.2 sulfuric acid solution. 134.

5.6.2.3 ammonium molybdate solution. 100g/L.

5.6.2.4 oxalic acid solution. 50g/L.

5.6.2.5 stannous chloride hydrochloric acid solution. 20g/L.

5.6.2.6 silica standard solution. 1mL solution containing silicon dioxide (SiO2) 0.02mg. Pipette by pipetting 2mL HG/T 3696.2 standard solution prepared silica, a 100mL volumetric flask, diluted with water to the mark. The solution was active Existing service.

5.6.2.7 saturated 2,4-dinitrophenol indicator solution.

5.6.3 Instruments and equipment

UV-visible spectrophotometer. with a 1cm cuvette.

5.6.4 Analysis of step

5.6.4.1 Preparation of test solution

Weigh about 1g sample, accurate to 0.01g, placed in a plastic beaker, adding a boric acid solution 40mL for sample dissolution. Transferred to 100mL Volumetric flask, diluted with water to the mark.

Draw standard curve 5.6.4.2 Pipette with a pipette 0.00mL, 0.50mL, 1.00mL, 2.00mL, 3.00mL, 4.00mL, 5.00mL standard silica Solution, were placed in a 50mL volumetric flask, add 2 drops of saturated 2,4-dinitrophenol indicator solution, sulfuric acid solution was added dropwise to the solution just eliminate yellow Loss, diluted to 10mL, 4.5mL was added a solution of sulfuric acid. Ammonium molybdate solution was added 2mL placed 20min. 5mL was added oxalic acid solution, Placed 5min. Add 0.2mL of stannous chloride hydrochloric acid solution, shake. Diluted with water to the mark. UV visible spectrophotometer, the at 795nm wavelength using a 1cm cuvette, zero water absorbance thereof was measured.

Reagent blank absorbance was subtracted from the absorbance of each standard solution, the silica mass (mg) as abscissa, the corresponding Absorbance as the ordinate, drawing working curve.

5.6.4.3 Determination

Pipette a quantity of pipette with a test solution (first-class goods take 5mL, take-defective 2 mL), was placed in a 50mL volumetric flask, according to the following

5.6.4.2 From the "plus 2 drops of a saturated solution of 2,4-dinitrophenol indicating" start to "measured absorbance" far. Blank test is to take an amount of boric acid solution (4 mL sample Take First, 0.8 mL of take-defective), a 50mL volumetric flask, and the same test solution at the same time Sample processing. Isolated test solution and the blank test solution from the mass of silica in the working curve.

5.6.5 Calculation results

Fluorosilicate, ammonium fluorosilicate content [(NH4) 2SiF6] w3 terms of mass fraction, (3) is calculated according to the formula.

(M1-m0) × 10-3 × 2.965 m (V/100) × 100% (3) where.

--- value M1 obtained from the working curve of the test solution to check the quality of the silica, in milligrams (mg);

--- value M0 from the working curve of the blank test solution Richard silica mass, in milligrams (mg);

Value m --- mass of the sample in grams (G);

Numerical solution of the test volume during pipetting V --- test, in milliliters (mL);

2.965 --- factor in terms of silica of ammonium fluorosilicate.

Parallel to the arithmetic average of the measurement results of the measurement result, the absolute difference determination results parallel to 0.02%.