Some standard content:
National Standard of the People's Republic of China
Main content and scope of application
Ammonium chloride
GB 2946-92
Replaces GB2946-82
This standard specifies the technical requirements, test methods, inspection rules, packaging, marking, transportation and storage of ammonium fluoride for industrial and agricultural use. This standard applies to ammonium fluoride for industrial and agricultural use. Its main uses: in industry, it is used in dry batteries, electroplating, dyeing and spinning, precision casting, etc., and in agriculture, it is used as a fertilizer.
Molecular formula: NH,CI
Relative molecular mass: 53.49 (according to the 1987 International Atomic Weight Table) Reference standards
GB 603
GB 6678
GB6679
GB8569
3 Product classification
Packaging, storage and transportation Pictorial signs
Preparation of standard solutions for titration analysis (volume analysis) of chemical reagents Preparation of standard solutions for determination of impurities of chemical reagents Preparation of preparations and products used in test methods of chemical reagents General rules for sampling of chemical products
General rules for sampling of solid chemical products
Packaging of solid chemical fertilizers
Ammonium fluoride products are divided into two categories: industrial ammonium chloride and agricultural ammonium fluoride. 4 Technical requirements
4.1 Appearance: white crystals or granules (granulated products). Agricultural use is allowed to be slightly gray or slightly yellow. 4.2 Industrial ammonium chloride shall meet the requirements of Table 1. 1 Industrial ammonium chloride
Ammonium fluoride (NH,CI) content (dry basis), %Moisture, %
Ignition residue, %
Iron (Fe) content, %
State Administration of Technical Supervision1992-06-29Approved31
First-class product
Qualified product
1993-05-01Implementation
Heavy metal (Pb) content, %
Sulfate (SO), %
pH value (200g/L solution, temperature 25C)
GB 2946-92
Continued Table 1
First-class product
4. 0~5. 8
Note: Moisture refers to the factory inspection result. When users have special requirements for moisture, the supply and demand parties can negotiate to resolve the issue. 4.3 Ammonium chloride for agricultural use shall meet the requirements of Table 2. Table 2 Ammonium fluoride for agricultural use
Indicator name
Nitrogen (N) content (on a dry basis), %
Moisture\, %
Sodium salt content (on a Na basis), %
Particle size 2 (1. 0~4. 0mm particles), %
Looseness 23 (aperture 5.0mm), %
Superior product
Note: 1) Moisture refers to the factory inspection result. Crystalline products must be added with anti-caking agents. First-class product
Qualified product
Qualified product
2) Crystalline products do not control the two indicators of particle size and looseness. 3) Looseness is a supervision sampling item. The test is conducted every seven days, and the results of factory inspection shall prevail, but the manufacturer must ensure that each batch of products leaving the factory is qualified. 5 Test method
The reagents and water used in the test method of this standard, unless otherwise specified, refer to analytical reagents and distilled water or water of equivalent purity.
The standard solutions, preparations and products prepared in the test method, unless otherwise specified, shall be prepared and calibrated in accordance with the provisions of GB601, GB602 and GB603.
5.1 Determination of ammonium chloride or nitrogen content Titration after distillation (arbitration method) 5.1.1 Principle
Ammonium chloride distills out ammonia in an alkaline solution, which is absorbed by an excess sulfuric acid standard solution. In the presence of an indicator solution, the excess sulfuric acid is titrated back with a sodium hydroxide standard titration solution.
5.1.2 Reagents and solutions
5.1.2.1 Sodium hydroxide (GB629): 450g/L solution; 5.1.2.2 Sulfuric acid (GB625): c(1/2H,SO,)=0.5mol/L, its concentration should be less than that of the standard titration solution of sodium hydroxide; 5.1.2.3 Standard titration solution of sodium hydroxide: c(NaOH)=0.5mol/L; 5.1.2.4 Methyl red-methylene blue mixed indicator solution; weigh 0.12g methyl red and 0.08g methylene blue, dissolve in 95% ethanol and dilute to 100mlL.
5.1.3 Instruments
General laboratory instruments.
5.1.3.1 Distillation apparatus: see the figure below or other distillation apparatus with the same efficiency. 375
GB2946-92
1000mL
Distillation flask (A): 1000mL, with No. 29 internal standard ground joint. Splash-proof ball tube (B): The end connected to the distillation flask has a No. 29 external standard ground joint, and the end connected to the condenser has a No. 19 b.
external standard ground joint.
Dropping funnel (C): Capacity is 50 mL.
Vertical condenser (D): Effective length is 400mm, inlet is No. 19 internal standard ground joint, outlet is No. 29 external standard ground joint. Absorption flask (E): 500mL, bottle mouth is No. 29 internal standard ground joint connected to double ball. 5.1.4 Analysis steps
5.1.4.1 Preparation of sample solution
Weigh about 9g of sample, accurate to 0.001g, place in a beaker, dissolve with water, transfer to a 500mL volumetric flask, dilute with water to the mark, shake and set aside.
5.1.4.2 Blank test
A blank test should be carried out during the determination. Except for not adding sample, the amount of reagents and the determination procedure are the same as those for the sample determination. The arithmetic mean of the parallel determination results is taken as the blank test value. 5.1.4.3 Distillation
Use a pipette to transfer 50.0mL of sample solution (5.1.4.1) into a distillation flask (A), add about 350mL of water, and then add a small amount of explosion-proof zeolite. Use a pipette to transfer 50.0mL of sulfuric acid standard solution into the absorption bottle (E), add about 80mL of water (water should be sufficient to seal the connection between the double ball and the bottle) and 46 drops of mixed indicator liquid. Connect the device according to the diagram, apply silicone grease or other fluorine-free lubricating oil to the connection, and fix it to ensure that the distillation device is tight and leak-proof. Pass cooling water into the condenser (D). 376
GB 2946-92
Inject 30mL of sodium hydroxide solution (51.2.1) into the distillation bottle (A) through the dropping funnel (C). When 2mL of solution remains in the funnel (C), close the piston.
Heat and distill until about 250mL of distillate is collected in the absorption bottle (E) (distillation time is about 45min), then stop heating. Then, open the piston on the funnel (C) and rinse with water, remove the splash-proof ball tube (B), carefully rinse the condenser (D), and collect the washing liquid in the absorption bottle (E), and remove the absorption bottle (E).
5.1.4.4 Titration
Carefully mix the solution in the absorption bottle (E) and the double ball, and use the sodium hydroxide standard titration solution to back-titrate the excess sulfuric acid in the absorption bottle (E) until the solution turns gray, which is the end point.
5.1.5 Expression of analysis results
5.1.5.1 The content of ammonium chloride is expressed as the mass percentage of ammonium chloride (NH.CI) and is calculated according to formula (1): r
wherein:
cV-V) × 0.05349 × 100-cy = VX 53.49ma)
m(l-r3)
~actual concentration of sodium hydroxide standard titration solution, mol/L, V——volume of sodium hydroxide standard titration solution consumed in blank test, mL; V——volume of sodium hydroxide standard titration solution consumed in test sample solution, mL; m—mass of sample, g;
....( 1)
Percentage of monohydrate:
0.05349----The mass of ammonium chloride in grams equivalent to 1.00mL of sodium hydroxide standard titration solution [c(NaOH)=1.000mol/LJ.
The result should be expressed to two decimal places.
5.1.5.2 Nitrogen content x2, expressed as mass percentage of nitrogen (N), is calculated according to formula (2): c(V - V2) × 0. 014 01
m(1 - r,) × 500
X 100 =
actual concentration of sodium hydroxide standard titration solution, mol/L; where: c——
c(V, - V2) × 14.01
m(1 - r,)
V,—volume of sodium hydroxide standard titration solution consumed in blank test, mL; V2 is the volume of sodium hydroxide standard titration solution consumed by the test sample solution,mL; m——mass of the sample, g;
·(2)
percentage of water;
mass of nitrogen in grams equivalent to 1.00mL of sodium hydroxide standard titration solution (c(NaOH)=1.000mol/LJ) 0.014 01
The results should be expressed to two decimal places.
5.1.6 Allowable difference
5.1.6.1 The arithmetic mean of the parallel determination results shall be taken as the determination result. 5.1.6.2 The absolute difference of the parallel determination results shall not exceed 0.20% for ammonium chloride and 0.05% for nitrogen. 5.1.6.3 The absolute difference of the determination results of different laboratories shall not exceed 0.30% for ammonium chloride and 0.08% for nitrogen. 5.2 Determination of ammonium chloride or nitrogen content Formaldehyde method 5.2.1 Principle
In a neutral solution, ammonium salt reacts with formaldehyde to generate hexamethylenetetramine and an acid equivalent to the ammonium salt content. In the presence of an indicator solution, the acid is titrated with a standard titration solution of 377
sodium cyanide.
5.2.2 Reagents and solutions
GB 2946—92
5.2.2.1 Sodium hydroxide (GB629): c(NaOH)=0.1mol/L solution; 5.2.2.2 Hydrochloric acid (GB 622): c(HQ1)=0. 1 mot/L solution; 5.2.2.3 Sulfuric acid (GB625) standard titration solution: c(1/2HSO)=1.0mol/L solution; 5.2.2.4 Sodium hydroxide (GB629) standard titration solution: c(Na()H)=0.5mol/L solution; 5.2.2.5 Methyl red: 1g/L ethanol solution; 5.2.2.6 Phenolic acid: 10g/L ethanol solution;
5.2.2 .7 Formaldehyde solution: 250g/L solution, prepared and calibrated as follows: a: Prepare with paraformaldehyde: weigh 280g paraformaldehyde (HGB3487), add 800mL water and 35mL ammonia water (GB621), heat to dissolve, cool to room temperature, filter, or let stand for 1 to 2 days, take the upper clear liquid, determine the formaldehyde content according to the method specified in (C), and then prepare a 250g/L formaldehyde solution.
Use reagent A Formaldehyde solution preparation: Place formaldehyde solution (GB685) in a distilling flask, slowly heat to about 96°C, and distill until the methanol content in the formaldehyde is less than 1% (distill until about one-tenth of the volume remains), then stop heating, and determine the formaldehyde content of the remaining solution according to the method specified in this article (C), and then prepare a 250g/L formaldehyde solution. c. Measurement of formaldehyde content: Transfer 50.0mL of sodium sulfite solution (126.0g of anhydrous sodium sulfite (HG31078) dissolved in water and diluted to 1000mL) into a 250mL conical flask, add 3~4 drops of phenol indicator solution, neutralize with sulfuric acid solution (1/2H2SO4) 1.0mol/L to light red, add 3.0mL of formaldehyde solution with a pipette, and titrate with the above sulfuric acid standard solution until the light red color does not disappear after 2 minutes. d. Formaldehyde content (g/I.) is calculated according to formula (3): C : V, X 0.030 03 × 100
: —-actual concentration of sulfuric acid standard titration solution.mol/I; V,----volume of sulfuric acid standard titration solution consumed in the determination, mL; V——volume of formaldehyde solution, mL;
0.03003.--mass of formaldehyde expressed in grams equivalent to 1.00ml sulfuric acid standard titration solution Cc (volume.
5.2.3 Instruments
General laboratory instruments.
5.2.4 Analysis steps
H2SO,)=1.000mol/L 5.2.4.1 Preparation of sample solution
Weigh about 0.9g of sample, accurate to 0.0002g, place it in a 250mL conical flask, add 30mL of water to dissolve it, add 1~~2 drops of methyl red indicator solution, and neutralize with hydrochloric acid or sodium hydroxide solution until it turns orange. 5.2.4.2 Blank test
A blank test should be carried out at the same time as the determination. Except that no sample is added, the reagent dosage and determination procedure are the same as those for the determination of the sample. The arithmetic mean of the parallel determination results is taken as the blank test value. 5.2.4.3 Determination
Add 15 ml of formaldehyde solution to the sample solution (5.2.4.1), then add 4~~5 drops of phenol indicator solution, shake well and let stand for 5 minutes, and titrate with sodium hydroxide standard titration solution until the solution pH is equivalent to 8.5 and a light red color appears. The end point is maintained for 1 minute without disappearing. 5.2.5 Expression of analytical results
5.2.5.1 The ammonium chloride content z1, expressed as the mass percentage of ammonium chloride (NH,CI), is calculated according to formula (4): Wide Fe Guang
In the formula:.
GB 2946-92
c(VV)×0. 053 49×100
m(1 -)
The actual concentration of the sodium hydroxide standard titration solution, mol/L; -The volume of the sodium hydroxide standard titration solution consumed in the blank test, mL; V
-The volume of the sodium hydroxide standard titration solution consumed by the test sample, mL; V
m-—The mass of the test sample, g
（4）
The percentage of water
The mass of ammonium fluoride in grams equivalent to 1.00mL of the sodium hydroxide standard titration solution (c(NaOH)=1.00mol/L).
The result should be expressed to two decimal places.
5.2.5.2 Nitrogen content T2, expressed as mass percentage of nitrogen (N), is calculated according to formula (5): c(V, -V) × 0. 014 01 × 1002 =
m(1 - αs)
wherein; c-
actual concentration of sodium hydroxide standard titration solution, mol/L; V,-volume of sodium hydroxide standard titration solution consumed in blank test, mL; V2-volume of sodium hydroxide standard titration solution consumed by test sample, mL,-mass of test sample, 8;
0. 014 01 -
Percentage of water;
Mass of nitrogen in grams equivalent to 1.00mL of standard sodium hydroxide titration solution (c(NaOH)=1.000mol/L).
The result should be expressed to two decimal places.
5.2.6 Allowable difference
5.2.6.1 The arithmetic mean of the parallel determination results shall be taken as the determination result. 5.2.6.2 The absolute difference of the parallel determination results shall not exceed 0.20% for ammonium chloride and 0.05% for nitrogen. 5.2.6.3 The absolute difference of the determination results of different laboratories shall not exceed 0.30% for ammonium chloride and 0.08% for nitrogen. 5.3 Determination of water content
Loss on drying method
5.3 .1 Principle
The sample is dried at 100-105℃ to constant weight, and the moisture content is calculated from the weight loss. 5.3.2 Instruments
General laboratory instruments.
5.3.2.1 Weighing bottle with ground stopper: diameter 50mm, height 30mm; 5.3.2.2 Electric drying oven: control temperature 100-105℃. 5.3.3 Analysis steps
Use a weighing bottle that has been dried and weighed at 100-105℃ in advance, weigh 5g of the sample, accurate to 0.001g, place it in a drying oven at 100-105℃, and dry it to constant weight (no more than 4h). 5.3.4 Expression of analysis results
Moisture content 3, expressed as the mass percentage of water (H,O), is calculated according to formula (6): m=ml× 100
（6）
Wherein m-
is the mass of the sample before drying, m;
is the mass of the sample after drying, m.
The result should be expressed to two decimal places.
5.3.5 Allowable error
GB2946-92
5.3.5.1 The arithmetic mean of the parallel determination results shall be taken as the determination result. 5.3.5.2 The absolute difference of the parallel determination results shall not exceed 0.05%. 5.4 Burning Determination of residue by gravimetric method
5.4.1 Principle
The sample is heated and sublimated, and then burned at 500-600℃ to constant weight to obtain the residue. Calculate the burning residue in the sample. 5.4.2 Instrument
General laboratory instruments.
5.4.2.1 Evaporation: quartz or porcelain evaporation, volume is 50mL, 5.4.2.2 High temperature furnace: control the temperature at 500-600℃5.4.3 Analysis steps
Weigh 10 samples, accurate to 0.01g, in 50mL evaporation III which has been burned to constant weight at 500~600℃, placed on an electric furnace for heating and sublimation, the sublimation temperature is about 400℃, until there is no white smoke, then transferred to a 500-600℃ high temperature furnace for burning, cooling, weighing, until constant weight.
5.4.4 Expression of analysis results
The burning residue is expressed as the mass percentage of the residue, calculated according to formula (7): m m2 × 100
where m is the mass of the evaporation residue after burning, m2-the mass of evaporation blood, g,
the mass of the sample, m.
The result should be expressed to two decimal places.
5.4.5 Tolerance
5.4.5.1 The arithmetic mean of the parallel determination results is taken as the determination result. 5.4.5.2 The absolute difference of the parallel determination results shall not exceed 0.05%. 5.5 Determination of iron content: o-phenanthroline spectrophotometric method 5.5.1 Principle
US 7)
Use ascorbic acid to reduce the trivalent iron in the sample to divalent iron. At pH 2-9, the divalent iron ions react with o-phenanthroline to form an orange-red complex. The absorbance is measured using a spectrophotometer at a wavelength of 510 nm. 5.5.2 Reagents and solutions
5.5.2.1 Hydrochloric acid (GB622): c(HCI) = 1.0 mol/L solution; 5.5.2.2 Ammonia (GB631): 1+9 solution; 5.5.2.3 Acetic acid (GB676)-sodium acetate (GB693) buffer solution: pH 4.5; 5.5.2.4 Ascorbic acid: 20 g/L solution, valid for 10 days; o-phenanthroline (GB1293): 2 g/L solution, when color is produced, it should be discarded and re-prepared. 5. 5.2. 54
5.5.2.6 Iron (Fe) standard solution: 0.1 mg/ml Weigh 0.864 g ammonium ferric sulfate CNHFe (SO,) 2·12H.O7 (GB1279) in a 200 mL beaker, add 100 mL water and Rntbzxz.net
GB 2946-92
10mL sulfuric acid (GB625), after dissolving, transfer to a 1000mL volumetric flask, dilute to scale with water, and shake well. 5.5.2.7 Iron (Fe) standard solution: 0.01 mg/L Use a pipette to transfer 25.0mL of iron standard solution (5.5.2.6) to a 250mL volumetric flask, dilute to scale with water, and shake well. This solution is prepared on the day of use.
5.5.3 Instruments
General laboratory instruments.
5.5.3.1 Spectrophotometer: Absorption cell with a thickness of 3cm. 5.5.4 Analysis steps
5.5.4.1 Preparation of sample solution
Weigh 2-5g of sample, accurate to 0.001g, place in a beaker, add about 30mL of water to dissolve, such as 510mL of hot acid solution, heat and boil for 25min, cool and such as ammonia bath, adjust the solution pH to close to 2 (check with precision pH test paper), transfer to a 100mL volumetric flask for determination.
5.5.4.2 Blank test
At the same time as the determination, a blank test should be carried out. Except for the difference between the sample and the sample, the amount of reagents and the determination procedure are the same as those for the determination of the sample. 5.5.4.3 Determination
Add 2.5mL of ascorbic acid solution, 10mL of buffer solution, and 5mL of o-phenanthroline solution to the sample solution and blank solution respectively, add water to the scale, shake and place for 15min. At a wavelength of 510 mm, use a 3 cm absorption cell and water as a reference, adjust the spectrophotometer's absorbance to zero, and then measure the absorbance of the test solution and the blank test solution.
Subtract the absorbance of the blank test from the measured absorbance of the sample solution, and find out the iron content corresponding to the absorbance from the standard curve. 5.5.4.4 Drawing of the standard curve
In a series of 100 ml volumetric flasks, add 0, 1.00, 2.00, 4.00, 6.00, 8.00 and 10.00 mL of the iron standard solution (5.5.2.7), add water to about 60 mL, 1.0 ml of hydrochloric acid, 2.5 ml of ascorbic acid solution, 10 ml of buffer solution, 5 ml of o-phenanthroline solution, dilute to the scale with water, shake well, and let stand for 15 minutes. At a wavelength of 510 nm, use a 3 cm absorption cell, take water as a reference, adjust the spectrophotometer absorbance to zero, measure the absorbance of the solution, subtract the absorbance of the reagent blank from the absorbance of each standard comparison solution, and draw a standard curve with the iron content as the horizontal axis and the corresponding absorbance as the vertical axis.
5.5.5 Representation of analysis results
The iron content s, expressed as the mass percentage of iron (Fe), is calculated according to formula (8): Lao Lan
m X 1 000
Where: m. The iron content in the test solution obtained from the standard curve, mg is the mass of the sample.
The result should be expressed to five decimal places.
5.5.6 Allowable difference
5.5.6.1 Take the arithmetic mean of the parallel determination results as the determination result. 5.5.6.2 The absolute difference of the parallel determination results shall not exceed 0.0002%. 5.5.6.3 The absolute difference between the results of different laboratories shall not exceed 0.0003%. 5.6 Determination of heavy metal content Visual turbidimetry (8)
5.6.1 Principle
In a weakly acidic medium, hydrogen sulfide combines with the hydrogen sulfide in the sample to form sulfide precipitation, and the solution is mixed. The turbidity of the solution is then compared with that of the lead standard to determine the heavy metal content in the sample. 5.6.2 Reagents and solutions
5.6.2.1 Lead nitrate (HG3-1070);
5.6.2.2 Acetic acid (GB676): 1+16 solution; 5.6.2.3 Lead (Pb) standard solution: 9.1 mg/mL; GB 2946-92
5.6.2.4 Lead (Pb) standard solution: 0.01 mg/mL; Use a pipette to transfer 10.0 ml of the lead standard solution (5.6.2.3) into a 100 mL volumetric flask, add water to the mark, and shake well. The solution should be prepared on the day of use.
5.6.2.5 Saturated hydrogen sulfide aqueous solution. Prepare on the day of use. 5.6.3 Instruments
General laboratory instruments and 50mL graduated colorimetric tubes with ground stoppers 5.6.4 Analysis steps
5.6.4.1 Preparation of standard turbidity
Add 2.5mL of lead standard solution (5.6.2.4) to a 50mL turbidimetric tube, add water to 35mL, add 2mL of acetic acid solution, 10mL of saturated hydrogen sulfide aqueous solution, dilute to scale with water, shake well and let stand for 10min. 5.6.4.2 Determination
Weigh 5g of sample, accurate to 0.01g, place in a beaker, add 20mL of water to dissolve and filter, filter the filtrate into a 50mL turbidimetric tube, wash the filter paper with a small amount of water several times, then add 2mL of acetic acid solution, add 10mL of saturated hydrogen sulfide aqueous solution with the lead standard solution, dilute to scale with water, shake well and let stand for 10min. The turbidity presented is compared with the standard turbidity. If the turbidity is lower than or equal to the standard turbidity, the heavy metal content (in terms of Pb) is ≤ 0.000 5%.
5.7 Determination of sulfate content
Visual comparison method
5.7.1 Principle
In an acidic medium, barium ions and sulfate ions generate barium sulfate. When the sulfate ion content is low, barium sulfate will be suspended for a certain period of time, making the solution turbid. The sulfate content in the sample can be determined by comparing the turbidity with the standard solution. 5.7.2 Reagents and solutions
5.7.2.1 95% ethanol (GB 679)
5.7.2.2 Anhydrous sodium sulfate (GB9853); hydrochloric acid (GB622): 1+1 solution;
sodium chloride (GB652): 100g/L solution; 5.7.2.4
Sulfate (SO) standard solution: 0.1mg/mL; 5.7.2.5
5.7.2.6 Ammonium chloride solution without sulfate: weigh 10g ammonium chloride sample, dissolve in 80mL water, add 1mL hydrochloric acid solution, boil, add 10mL barium chloride solution, stir well, place for 12-18h, filter, and dilute to 100mL. 5.7.3 Instruments
~General laboratory instruments and 50mL graduated tubes with ground stoppers. 5.7.4 Analysis steps
5.7.4.1 Preparation of standard turbidity
In a 50mL turbidimetric tube, add 2.0mL of sulfate standard solution, add water to 25mL, and add 10mL of sulfate-free ammonium nitride solution. Then add 5mL of 95% ethanol, 1mL of hydrochloric acid solution, and 5mL of barium chloride solution, dilute to the scale with water, shake well, and let stand for 20 minutes.
5.7.4.2 Determination
Weigh 1g of sample, accurate to 0.01g, put it in a beaker, add 20mL water to dissolve and filter, filter the filtrate into a 50mL turbidimetric tube, wash the filter paper several times with a small amount of water, then add 5mL 95% ethanol, 1mL hydrochloric acid solution, and 5mL barium chloride solution at the same time as the sulfate standard, add water to dilute to the scale, shake well and let it stand for 20 minutes. Compared with the standard turbidity, the turbidity is lower than or equal to the standard turbidity, that is, the sulfate content (in terms of S0,) is ≤0.02%. 5.8 Determination of sodium content Flame photometry 5.8.1 Principle GB2946-92 When the solution of the element to be measured is sprayed into the flame, the characteristic spectrum of the element can be emitted. Within a certain concentration range, the intensity of the characteristic spectrum line is proportional to the concentration of the element. The intensity of the characteristic spectrum line of the element to be measured can be measured and the sodium content in the sample can be obtained by the calibration curve method. 5.8.2 Reagents and solutions
5.8.2.1 Sodium chloride (GB1253) Standard reagent 5.8.2.2 Ammonium chloride (GB658): high-grade pure, 100g/L solution 5.8.2.3 Sodium standard solution: 1mL is equivalent to 0.5mg sodium Weigh 1.271g sodium chloride that has been burned to a mass at 500~600℃ in a 250mL beaker, dissolve it with water, transfer it to a 1000mL volumetric flask, dilute to the mark, and shake well. 5.8.2.4 Sodium calibration solution: 1ml. Equivalent to 0.02mg sodium: Use a pipette to transfer 10.0mL of sodium standard solution (5.8.2.3) to a 250mL volumetric flask, add 3mL of ammonium chloride solution, dilute to the mark with water, and shake well.
5.8.3 Instruments
General laboratory instruments.
5.8.3.1 Flame photometer
5.8.3.2 Fuel gas and compressed air.
5.8.4 Analysis steps
5.8.4.1 Preparation of sample solution
Weigh 3 samples accurately to 0.001g, place in a beaker, dissolve with water, transfer to a 250mL volumetric flask, dilute to scale, and shake well. Take out 25mL of the sample solution and place in another 250mL volumetric flask, dilute to scale, and shake well. 5.8.4.2 Calibration test
Perform the calibration test using the sodium calibration solution (5.8.2.4) as specified in the flame photometer instruction manual. 5.8.4.3 Determination
Perform the test of the sample solution as specified in the flame photometer instruction manual. After repeating three times, calculate the average value of the characteristic spectral line intensity, and then find the corresponding amount of sodium (m) on the standard curve from the average value of the characteristic spectral line intensity. The differential method (standard comparison method) can also be used. Draw the standard curve (5.8.4.4) From the standard series, select two standard solutions close to the concentration of the sample solution, and use the low concentration to adjust the instrument pointer to zero. Use the high concentration standard solution to measure the intensity of the characteristic spectrum, and then measure the sample solution. 5.8.4.4 Drawing of the standard curve
In several 250mL volumetric flasks, add 1.0, 2.0, 3.0, 6.0, 8.0.10.0mL of sodium standard solution and 3mL of ammonium chloride solution, respectively, dilute to the scale with water, and shake well. The following operations are calibrated and measured according to the flame photometer instruction manual. Draw the standard curve with the sodium content as the horizontal axis and the corresponding characteristic spectrum line intensity as the vertical axis. 5.8.5 Expression of analytical results
5.8.5.1 The sodium content xs is expressed as the mass percentage of sodium (Na) and is calculated by the standard curve method according to formula (9): #e×0.001×100=
m×250
Wherein: m, - the mass of sodium corresponding to the sample solution obtained from the standard curve, mgm, the mass of the sample·2,
The result should be expressed to two decimal places
GB 2946-- 92
5.8.5.2 The sodium content s is expressed as the mass percentage of sodium (Na) and is calculated by the differential method according to formula (10): m
Wherein: m
X (m - mz)
Select the mass of sodium contained in the low concentration standard solution, ngm.-Select the mass of sodium contained in the high concentration standard solution, mg; I. Measure the characteristic spectral line intensity of the sample solution concentration, 12-the characteristic spectral line intensity of the high concentration standard solution; - the mass of the sample, g.
The result should be expressed to two decimal places.
5.8.6 Allowable difference
5.8.6.1 Take the arithmetic mean of the parallel determination results as the determination result. 5.8.6.2 The absolute difference of the parallel determination results shall not exceed 0.06%. m.
5.8.6.3 The absolute difference of the determination results of different laboratories shall not exceed 0.15%. 5.9 Determination of pH value Potentiometric method X (ma - m2) (10) 5.9.1 Principle Using a pH meter equipped with a glass electrode and a calomel electrode, determine the pH value of a fluoride solution at a concentration of 200/L and a temperature of 25 ± 1°C. 5.9.2 Reagents and solutions 5.9.2.1 All reagents used are basic reagents or reagents of superpure grade or above. The water used is distilled water without carbon dioxide. 5.9.2.2 Potassium dihydrogen phosphate Lc (KHPO4) = 0. 025 mol/L and disodium hydrogen phosphate Lc (NazHPO4) = 0.025 mol/L Buffer solution: Weigh 3.40 g of dihydrogen phosphate (KHPO4) and dissolve it in about 400 nL of water. Weigh 3.55g of disodium hydrogen phosphate (NazHPO) and dissolve it in about 400mL of water. Transfer the two solutions to a 1000mL volumetric flask, dilute to the mark with water, and shake well. Store this solution in a sealed container. The pH value of this buffer solution is 6.86 at 25°C. 5.9.2.3 Potassium hydrogen phthalate (Ec (CH, OK) = 0.05mol/L) buffer solution: Weigh 10.21g of potassium hydrogen phthalate, dissolve it in water, transfer it to a 1000mL volumetric flask, dilute to the mark with water, and shake well. This solution should be stored in a sealed container. The pH value of this buffer solution is 4.01 at 25°C. 5.9.3 Instruments
General laboratory instruments.
5.9.3.1 pH meter with glass electrode and calomel electrode, with a sensitivity of 0.1pH. 5.9.4 Analysis steps
5.9.4.1 Preparation of sample solution
Weigh 20g of sample to the nearest 0.1g and place in a suitable beaker. Add water to 100mL and adjust the solution temperature to 25±1℃.
5.9.4.2 Calibration of pH meter
Calibrate the pH meter with buffer solutions (5.9.2.2) and (5.9.2.3) at 25±1℃. 5.9.4.3 Determination
Insert the two electrodes of the pH meter into the sample solution beaker and measure under the same conditions as during calibration. The pH value of the ammonium cyanide solution is expressed in pH. The result is expressed to one decimal place. 5.10 Determination of particle size Sieving method
5.10.1 Summary of method
The sample is vibrated and sieved in the test sieve, and the percentage of particles with a diameter of 1.0~~4.0 mm is measured. 5.10.2 Instrument
General laboratory instruments and test sieves with a pore size of 1.0 mm and 4.0 mm, with lid and sieve bottom, conforming to GB 6003 R zero series. 5.10.3 Analysis steps
Stack the test sieves with a pore size of 4.0 mm and 1.0 mm from top to bottom in order of pore size, and install the sieve bottom. Weigh 200g of the particle sample, accurate to 0.5g, place it on the 4mm sieve, cover the sieve cover, and sieve it by mechanical vibration or manual horizontal vibration, with a vibration cheek rate of about 80 times per minute. After 2 minutes, move the sample left on the sieve with a pore size of 1.0 mm into the surface blood and weigh it. 5.10.4 Expression of analysis results
Particle size (1.0~~4.0mm)zz, expressed as mass percentage, calculated according to formula (11): m×100
Where: m is the mass of granular ammonium fluoride retained on the 1.0 mm aperture sieve, g - the mass of the sample, g.
5.11 Determination of bulkiness Gravimetric method
·(11)
5.11.1 Summary of the method
Let the bagged sample, which has been piled for a certain period of time, fall freely from a height of 1m onto a hard plane, and then sieve it. Weigh the mass of the sample retained on the sieve and calculate the bulkiness.
5.11.2 Instruments and equipment
5.11.2.1 Metal mesh wooden frame screen: industrial screen, aperture 5.0mm; specification 950×600×120, 5.11.2.2 Stopwatch: 60s,
5.11.2.3 Scale:10 kg.
5.11.3 Analysis steps
Stack the products to be tested into a stack of more than seven packages. After 7 days, take the seventh package from the top as the test sample (or use a single package and press a steel plate on it. The steel plate and the upper load are equivalent to the mass of 6 packages). Use a mechanical device or manual to drop the test sample package horizontally from a height of 1m to a hard plane. Then, pour the sample in the package into the sieve for screening. Use a mechanical device or manual to swing the sieve horizontally, with a swing frequency of 50±10 times/min, a swing distance of not less than 30cm, and a screening time of 1min. It is allowed to pinch the large pieces on the sieve by hand and sieve again, and weigh the mass of the sample left on the sieve.
5.11.4 Expression of analysis results
The bulkiness g, expressed as a percentage of the sieved mass, is calculated according to formula (12): Ca
Wherein: m1——mass of the sample remaining on the sieve after sieving, kg; m—mass of the sample in the bag before sieving, kg.
6 Inspection rules
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6.1 Ammonium fluoride products shall be inspected by the quality inspection department of the manufacturer in accordance with the inspection method specified in this standard. The manufacturer shall ensure that all 385
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