Some standard content:
National Standard of the People's Republic of China
Ammonium sulphate
Subject content and scope of application
Generation 07
This standard specifies the technical requirements, test methods, inspection rules, as well as marking, packaging, transportation and storage of ammonium sulphate. This standard is applicable to ammonium sulphate produced by the reaction of synthetic ammonia and sulfuric acid, by-product ammonium sulphate produced by coking, and is not applicable to by-product ammonium sulphate products produced by desulfurization process in thermal power plants or other flue gas desulfurization processes. Molecular formula: (NH,), SO)
Relative molecular mass: 132, 141 (according to the 1989 International Relative Atomic Mass)2
Cited standards
GB/T 601
GB/T 602
GB/T 603
GB/T 611
GB 1250
Chemical reagentsPreparation of standard solutions for titration analysis (volume analysis) of chemical reagentsPreparation of standard solutions for determination of impurities of chemical reagentsPreparation of preparations and products used in test methods of chemical reagentsGeneral method for determination of density of chemical reagents
Expression and determination methods of limit valuesSpecifications and test methods for water used in analytical laboratoriesGB/T 6682
G138569 Packaging of solid chemical fertilizers
3 Technical requirements
3.1 The quality of ammonium sulfate shall meet the requirements of Table 1: Table 1
Superior products
White crystals, no visible mechanical impurities
Nitrogen () content (on dry basis)
Water (H.0)
Free acid (H2S()) content
Iron (Fc) content
Arsenic (As) content
Heavy metal (as Pb) content:
Water-insoluble matter content
Superior products
No visible mechanical impurities
Note: 1) When ammonium sulfate is used for agriculture, it is not necessary to test the content of iron, arsenic, heavy metals and water-insoluble matter. Approved by the State Administration of Technical Supervision on December 20, 1995 20
Qualified products
Implemented on August 1, 1996
4 Test methods
GB 535--- 1995
In the analysis, unless otherwise specified, analytical reagents are used; the water used should meet the specifications of grade 3 water (only pH range and conductivity determination) in GB/T6682; all standard solutions for titration analysis are prepared and calibrated according to GB/T601; all standard solutions for impurity determination are prepared according to GB/T602; all preparations and products used in the test methods are prepared according to GB/T603. 4.1 Appearance
Visual inspection.
4.2 Determination of nitrogen content Titration after distillation (arbitration method). This method is equivalent to ISO333275 "Ammonium sulfate for industrial use-~Determination of nitrogen content--Titration after distillation". 4.2.1 Method Summary
The ammonia distilled from ammonium sulfate in alkaline solution is absorbed by excess sulfuric acid standard titration solution, and excess sulfuric acid is back-titrated with sodium hydroxide standard titration solution in the presence of an indicator. 4.2.2 Reagents and Materials
4.2.2.1 Sodium hydroxide (GB/T629), 450g/L solution; 4.2.2.2 Standard titration solution of sulfuric acid (GB/T625), c÷H,SO,) = 0.5mol/L; 4.2.2.3 Standard titration solution of sodium hydroxide, c(NaOH) = 0.5mol/I.; 4.2.2.4 Methyl red-methylene blue mixed indicator; Dissolve 0.1g methyl red (HG/T3-958) in 50mL ethanol (GB/T679), then add 0.05g methylene blue, and after dissolution, dilute to 100mL with the same ethanol.
4.2.2.5 Silicone grease or other nitrogen-free grease. 4.2.3 Apparatus and equipment
General laboratory instruments and:
4.2.3.1 Distillation apparatus
The apparatus used in this method is shown in Figure 1:
Distillation flask (A): volume 1L;
Splash-proof ball tube (B): inserted in parallel with the dropping funnel (C); Dropping funnel (C): volume 50mL;
Straight condenser (D): effective length about 400mm; Absorption bottle (E): volume 500ml, double balls connected to the bottle side. 21
GB535-1995
Figure 1 Distillation apparatus
4.2.3.2 Anti-boiling stone or anti-boiling device, the latter consists of a 100mm long, 5mm diameter glass rod connected to a 25mm long polyethylene tube.
4.2.4 Analysis steps
4.2.4.1 Preparation of sample solution
Weigh 10 g of sample to the nearest 0.001 g, dissolve in a small amount of water, transfer to a 500 mL volumetric flask, dilute to scale with water, and mix. 4.2.4.2 Distillation
Pipette 50.0 mL of test solution from the volumetric flask (4.2.4.1) into the distillation flask (A), add about 350 mL of water and a few grains of anti-riot zeolite (or anti-riot device: touch the polyethylene tube to the bottom of the flask). Use a single-line pipette to add 50 mL of sulfuric acid standard titration solution into the absorption bottle (E), and add 80 mL of water and 5 drops of mixed indicator solution.
Coat the instrument interface with silicone grease, install the distillation instrument according to Figure 1, and ensure that all parts of the instrument are sealed. Inject 20 mL of sodium hydroxide solution (4.2.2.1) into the distillation flask (A) through the dropping funnel (C), and make sure that at least a few milliliters of solution remain in the dropping funnel.
Heat and distill until the amount collected in the absorption flask (E) reaches 250-300 mL. Stop heating, open the dropping funnel (C), remove the splash-proof bulb (B), rinse the condenser (D) with water, and collect the washing liquid in the absorption flask (E), and remove the absorption flask. 4.2.4.3 Titration
Mix the solution in the absorption flask (E), and back-titrate the excess sulfuric acid standard titration solution with the sodium hydroxide standard titration solution (4.2.2.3) until the indicator turns gray-green, which is the end point.
4.2.4.4 Blank test
GB535-1995
During the determination, except for not adding the sample, the same analytical steps, reagents and dosages as in 4.2.4.1 to 4.2.4.3 are used for parallel operation.
4.2.5 Expression of analytical results
Nitrogen (N) content (ri, dry basis), expressed as mass percentage (%), is calculated according to formula (1): T
(V - V1)c × 0. 014 01
100-H,0
(V2 - Vi)c × 1 401
m(100 -
Wherein: V,—the volume of sodium hydroxide standard titration solution used in the determination, mL; V---the volume of sodium hydroxide standard titration solution used in the blank test, mL; actual concentration of sodium hydroxide standard titration solution, mol/L; m-the mass of the sample, g;
H,O-the percentage of water in the sample;
(1)
0.01401--the equivalent of 1.00mL sodium hydroxide standard titration solution Cc(NaOH)=1.000mol/LJ The mass of nitrogen expressed in grams.
4.2.6 Allowable difference
The arithmetic mean of the parallel determination results shall be taken as the determination result. The absolute difference of the parallel determinations shall not exceed 0.06%; the absolute difference of the determination results of different laboratories shall not exceed 0.12%. 4.3 Determination of nitrogen content Formaldehyde method
4.3.1 Method summary
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, titrate with a standard sodium hydroxide titration solution. ||t t||4.3.2 Reagents and materials
4.3.2.1 Sodium hydroxide (GB/T629), 4g/L solution; 4.3.2.2 Standard sodium hydroxide titration solution c(NaOH) = 0.5mol/L; 4.3.2.3 Formaldehyde, 250g/L solution;
Prepare and measure according to Appendix A.
4.3.2.4 Methyl red (HG/T3-958) indicator solution, 1g/L ethanol (GB/T678) solution; 4.3.2.5 Phenolic acid (GB/T 10729) indicator solution, 10g/L ethanol (GB/T678) solution. 4.3.3 Analysis steps
4.3.3.1 Preparation of sample solution
Weigh 1g of sample, accurate to 0.001g, place in a 250mL conical flask, add 100-120mL of water to dissolve, then add 1 drop of methyl red indicator solution, and adjust with sodium hydroxide solution (4.3.2.1) until the solution turns orange. 4.3.3.2 Determination
Add 15mL of formaldehyde solution to the test solution (4.3.3.1), add 3 drops of phenolic acid indicator solution and mix. Let stand for 5 minutes, and titrate with sodium hydroxide standard titration solution (4.3.2.2) until light red color does not disappear after 1 minute (or titrate to pH 8.5 indicated by pH meter) as the end point. 4.3.3.3 Blank test
During the determination, except for not adding the sample, the same analytical steps, reagents and dosages as 4.3.3.1 and 4.3.3.2 are carried out in parallel.
4.3.4 Expression of analysis results
Nitrogen (N) content (2, dry basis), expressed as mass percentage (%), is calculated according to formula (2): 23
Wherein: V,-
GB535—1995
(V, -- V,) : c X 0. 014 01
× 100
100-X,0
(V1-V2) ·c X 140. 1
m(100 -- XH,0)
The volume of sodium hydroxide standard titration solution used in the determination, mL; V2—the volume of sodium hydroxide standard titration solution used in the blank test, mL; the actual concentration of sodium hydroxide standard titration solution, mol/L; m-
---the mass of the sample, g;
TH,O—-the percentage of water in the sample;
. (2)
The mass of nitrogen in grams equivalent to 1.00ml of sodium hydroxide standard titration solution Cc (NaOH) = 1.000mol/L).
4.3.5 Allowable difference
The arithmetic mean of the parallel determination results is taken as the determination result. The absolute difference of the parallel determination results shall not exceed 0.06%; the absolute difference of the determination results of different laboratories shall not exceed 0.12%. 4.4 Determination of moisture content Gravimetric method
4.4.1 Summary of the method
In an electric constant temperature drying oven at a certain temperature, dry the sample to constant weight, and then measure the reduced mass of the sample. This method is applicable to the sample with a moisture content of not less than 0.001g. 4.4.2 Instruments and equipment
General laboratory instruments and:
4.4.2.1 Ground-mouth weighing bottle with cover, 50mm in diameter and 30mm in height; 4.4.2.2 Electric constant temperature drying oven, capable of maintaining a temperature of 105±2℃. 4.4.3 Analysis steps
Weigh 5g of sample, accurate to 0.0002g, and place it in a weighing bottle (4.4.2.1) that has been dried to constant weight at 105±2℃ in advance. Slightly open the lid of the weighing bottle and place it in a drying oven at a level close to the mercury ball of the thermometer. After drying at 105±2℃ for 30min, take out the weighing bottle, cover it, cool it to room temperature in a desiccator and weigh it. Repeat the operation until constant weight is reached. The last measured value is taken as the determination result.
4.4.4 Expression of analysis results
Water (H2O) (:), expressed as mass percentage (%), is calculated according to formula (3): 3
ml - m2 × 100
Where: m1--mass of weighing bottle and sample before drying, g; m. mass of weighing bottle and sample after drying.
.--mass of sample.
4.4.5 Allowable difference
The arithmetic mean of the parallel determination results is taken as the determination result, and the absolute difference of the parallel determination results shall not exceed 0.05%. 4.5 Determination of free acid content·Volume method
This method is equivalent to ISO2993--74 "Determination of free acidity of industrial ammonium sulfate titration method". 4.5.1 Method summary
The free acid in the sample solution is titrated with sodium hydroxide standard titration solution in the presence of an indicator. 4.5.2 Reagents and materials
4.5.2.1 Sodium hydroxide (GB/T629) standard titration solution, c(Na()H)=0.1mol/L; 24
（3）
GB 5351995
4.5.2.2 Hydrochloric acid (GB/T622) solution, c(HC1)=0.1mol/I; 4.5.2.3 The preparation method of methyl red-methylene blue mixed indicator is the same as 4.2.2.4.
4.5.2.4 Water used in analysis
Add 2 to 3 drops of indicator solution (4.5.2.3) to 1000 mL of water. If the solution is not gray-green, use sodium hydroxide solution (4.5.2.1) or hydrochloric acid solution (4.5.2.2) to adjust the solution to gray-green (or the pH meter indicates pH 5.4 to 5.6). 4.5.3 Instruments and equipment
General laboratory instruments and:
4.5.3.1 Microburette, 5 mL, graduation value 0.02 mL; 4.5.3.2 Acidometer.
4.5.4 Analysis steps
Weigh 10g of the sample, accurate to 0.01g, place it in a 100ml beaker, add 50ml of water (4.5.2.4) to dissolve. If the solution is turbid, filter it with medium-speed filter paper, wash the beaker and filter paper with water (4.5.2.4), and collect the filtrate in a 250mL conical flask. Add 1 to 2 drops of indicator solution to the filtrate, and titrate with sodium hydroxide standard titration solution until it turns gray-green as the end point. If the test solution is colored and the end point is difficult to observe, it can also be titrated until the pH meter indicates pH 5.4 to 5.6 as the end point. 4.5.5 Expression of analytical results
Free acid (H,SO) content (x4), expressed as mass percentage (%), is calculated according to formula (4): × 0. 049 0 × 100 = 9
-actual concentration of sodium hydroxide standard titration solution, mol/L; where: c-
V-volume of sodium hydroxide standard titration solution used in the determination, mL; m-mass of the sample, g;
cV × 4. 90
0.0490-mass of sulfuric acid in grams equivalent to 1.00mL sodium hydroxide standard titration solution Lc(NaOH)=1.000mol/L>.
4.5.6 Allowable difference
The arithmetic mean of the parallel determination results is taken as the determination result. The absolute difference of the parallel determination results shall not be greater than: free acid content, %
Absolute difference, %
The absolute difference of the determination results of different laboratories shall not be greater than: free acid content, %
4.6 Determination of iron content o-phenanthroline spectrophotometric method 4.6.1 Method summary
Absolute difference, %
After the iron in the sample is dissolved with hydrochloric acid, the trivalent iron is reduced to divalent iron with ascorbic acid. In the buffer medium (pH2-9), the divalent iron and o-phenanthroline generate an orange-red complex. The absorbance is determined by a spectrophotometer at the maximum absorption wavelength of 510nm. This method is suitable for the determination of test solutions with iron content in the range of 10-100 μg. 4.6.2 Reagents and materials
Instructions:
1] ISO2993--74 uses methyl violet (pH 5.2-5.6) or other indicators with the same pH range, this standard uses methyl red-methylene blue mixed indicator (color change point pH 5.4).
GB 535--1995
Hydrochloric acid (GB/T 622) solution, c(HC1)-1 mol/L;4.6.2.1
4.6.2.2 Sulfuric acid (GB/T625);
4.6.2.3 Ammonia water (GB/T631), 1+2 solution;4.6.2.4 Ascorbic acid solution, 100 g/L, the solution is stable within one week;4.6.2.5 Acetic acid (GB/T676)-sodium acetate (GB/T693) buffer solution, pH=4.5;4.6.2.6 O-phenanthroline (GB/T1293) solution, 1 g/L; The solution should be kept away from light, and only the colorless solution can be used. 4.6.2.7 Iron standard solution, 0.100 g/L; weigh 0.863 g of ammonium ferric sulfate (GB/T1279) to an accuracy of 0.001 g, dissolve in 200 mL of water, add 10 mL of sulfuric acid (4.6.2.2), transfer quantitatively to a 1000 mL volumetric flask, dilute to scale, and mix. This solution contains 0.100 mg of iron in 1 mL. 4.6.2.8 Iron standard solution, 0.010 g/L; aspirate 50.0 mL of iron standard solution (4.6.2.7) in a 500 mL volumetric flask, dilute to scale, and mix. This solution contains 10 μg of iron in 1 mL, and is prepared when used.
4.6.3 Instruments and equipment
General laboratory instruments and:
4.6.3.1 Spectrophotometer with an absorption cell with a light path length of 3 cm; 4.6.3.2 Wide range pH test paper or pH meter.
4.6.4 Analysis steps
4.6.4.1 Drawing of standard curve
a.Preparation of standard colorimetric solution
As shown in Table 2, add the given volume of iron standard solution (4.6.2.8) to a series of 100mL beakers. Table 2
Iron standard solution (4.6.2.8)
Corresponding iron content
Each beaker is treated in the same way as follows: Iron standard solution (4.6.2.8)
Corresponding iron content
Add water to 30mL and use hydrochloric acid solution (4.6.2.1) or ammonia solution (4.6.2. 3) Adjust the pH value of the solution to close to 2, transfer the solution quantitatively to a 100mL volumetric flask, add 1mL ascorbic acid solution, 20mL buffer solution and 10.0mL o-phenanthroline solution, dilute to the mark with water, mix well, and let stand for 15-30min. b. Photometric determination
Use a 3cm absorption cell and a solution with zero iron content as the reference solution. Use a spectrophotometer to determine the absorbance of the standard colorimetric solution (4.6.4.1a.) at a wavelength of 510nm. c. Draw a standard curve
Use 100 The number of micrograms of iron contained in mL of standard colorimetric solution is the horizontal axis, and the corresponding absorbance is the vertical axis. Draw a graph. 4.6.4.2 Determination
a. Preparation of sample solution
Weigh 10g of sample, accurate to 0.01g, place in a 100mL beaker, add a small amount of water to dissolve, add 10mL of hydrochloric acid solution (4.6.2.1), heat and boil for 2min, transfer quantitatively to a 100mL volumetric flask after cooling, dilute to scale, and mix. b. Color development
GB535-1995
Absorb 10 .0mL test solution (4.6.4.2a.) is placed in a 100mL beaker and color developed as specified in 4.6.4.1a., starting from "add water to 30mL" to "stand for 15-30min". c. Photometric determination
Determine the absorbance of the test solution in the same manner as specified in 4.6.4.1b. Find the mass of iron (μg) corresponding to the absorbance of the test solution from the standard curve (4.6.4.1c.). 4.6.5 Iron (Fe) content (zs), expressed as mass percentage (%), is calculated according to formula (5): αs
× 100 =
m×100
Where: mo--
The mass of iron (Fe) measured in the test solution, μg; -The mass of the sample, g.
4.6.6 Allowable difference Www.bzxZ.net
m × 103
The arithmetic mean of the parallel determination results is taken as the determination result. The absolute difference of the parallel determination results shall not exceed 0.0005%; the absolute difference of the determination results of different laboratories shall not exceed 0.0010%. · (5)
4.7 Determination of arsenic content Silver diethyldithiocarbamate spectrophotometric method (arbitration method) This method is equivalent to ISO5786-78 "Industrial ammonium sulfate-determination of arsenic content Silver diethyldithiocarbamate spectrophotometric method".
4.7.1 Method summary
In an acidic medium, potassium iodide, stannous chloride and metallic zinc reduce arsenic to arsine, which reacts with the pyridine solution of silver diethyldithiocarbamate to generate purple-red colloidal silver, and its absorbance is measured at the maximum absorption wavelength of 540nm. This method is suitable for the determination of test solutions with arsenic content in the range of 1 to 20ug.
4.7.2 Reagents and materials
4.7.2, 1 Hydrochloric acid (GB/T622);
4.7.2.2 Arsenic-free zinc particles (GB/T2304); 4.7.2.3 Potassium iodide (GB/T1272) solution, 150g/L; 4.7.2.4 Stannous chloride (GB/T638), 400g/L hydrochloric acid solution; Dissolve 40g of stannous chloride in a mixture of 25mL water and 75mL hydrochloric acid (4.7.2.1). 4.7.2.5 Silver diethyldithiocarbamate, referred to as Ag (DDTC) J-pyridine (GB/T689) solution, 5g/L; Dissolve 1g of Ag (DDTC) in pyridine and dilute to 200mL with the same pyridine. Store in a brown bottle. The solution is stable within two weeks.
4.7.2.6 Arsenic standard solution, 0.100g/L; 1ml of this solution contains 100μg of arsenic.
4.7.2.7 Arsenic standard solution, 0.0025g/L; Pipette 25.0mL of arsenic standard solution (4.7.2.6) into a 1000mL volumetric flask, dilute to the mark with water, and mix well. 1ml of this solution contains 2.5ug of arsenic, and is prepared before use.
4.7.2.8 Lead acetate (HG/T3-974) cotton; 4.7.3 Instruments and equipment
The glass container used for arsenic determination must be washed with concentrated sulfuric acid-potassium dichromate washing solution, then cleaned with water, and dried for use. General laboratory instruments and:
4.7.3.1 Arsenic determination instrument
As shown in Figure 2, or other arsenic determination instruments that have been proven by experiments to give the same results under the specified test conditions. Conical flask (A): volume 100mL, used for arsenic release; a.
Connecting tube (B): filled with lead acetate cotton before use; b.
GB 5351995
c.15 bulb absorber (C): total height about 250mm, total volume 14mL. 4.7.3.2 Spectrophotometer, with an absorption cell with a light path length of 1cm. d14
Figure 2 Arsenic determination instrument
4.7.4 Analysis steps
Since pyridine has a foul odor, the operation should be carried out in a fume hood. 4.7.4.1 Drawing of standard curve
a. Preparation of standard colorimetric solution
According to Table 3, take the arsenic standard solution (4.7.2.7) and place it in 6 conical flasks (A) (4.7.3.1a.) respectively. 28
Arsenic standard solution (4.7.2.7)
GB 535--1995
Corresponding arsenic content
Arsenic standard solution (4.7.2.7)
Corresponding arsenic content
Each conical flask (A) is diluted with water to 50mL, and 15mL hydrochloric acid (4.7.2.1) is added, and then 2mL potassium iodide solution and 2mL stannous chloride solution are added in sequence, mixed, and left for 15min. Place a small amount of lead acetate cotton in the connecting tube (B) (4.7.3.1b.) to absorb hydrogen sulfide. Absorb 5.0mL Ag (DDTC)-pyridine solution into the 15-bulb tube absorber (C) (4.7.3.1c.), and connect the instrument according to Figure 2. The ground glass joint should remain sealed during the reaction. Weigh 5g of zinc particles and add them to the conical flask. Quickly connect the instrument and allow the reaction to proceed for about 45min. Remove the absorber and fully mix the solution to generate purple-red colloidal silver.
b. Photometric determination
Use the solution with zero arsenic content as the reference solution and use a 1cm absorption cell to measure the absorbance of the standard colorimetric solution (4.7.4.1a.) at a wavelength of 540nm using a spectrophotometer.
c. Draw a standard curve
Draw a standard curve using the micrograms of arsenic contained in 5.0mL.Ag(DDTC)-pyridine solution absorption solution (4.7.2.5) as the horizontal axis and the corresponding absorbance as the vertical axis.
4.7.4.2 Determination
a. Preparation of sample solution
Weigh 20g of sample, accurate to 0.001g, place in a conical flask (A), add 50mL of water, mix to completely dissolve, add 15mL of hydrochloric acid (4.7.2.1), make the concentration of hydrochloric acid in the resulting solution about c(HCI)=3mol/L, mix. b. Colorimetric and photometric determination
Add 2mL of potassium iodide solution and 2mL of stannous chloride solution to the test solution (4.7.4.2a.), mix and let stand for 15min. The following steps are followed in accordance with the procedures specified in 4.7.4.1a. and 4.7.4.1b., starting from "Put a small amount of lead acetate cotton in the connecting tube (B) ....\" until "...Use a spectrophotometer to measure the absorbance of the solution". The mass of the monument (μg) corresponding to the absorbance of the test solution is found from the standard curve (4.7.4.1c.). 4.7.5 Arsenic (As) content (%), expressed as mass percentage (%), is calculated according to formula (6): 26
× 100
m X 106
Where: m. - mass of arsenic (As) measured in the test solution, μg; - mass of the sample, g.
Take the arithmetic mean of the parallel determination results as the determination result. 4.8 Determination of arsenic content Arsenic spot method
4.8..1 Summary of the method
m × 10%
In an acidic medium, potassium iodide, stannous chloride and metallic zinc reduce the arsenic in the test solution to hydrogen, which then reacts with mercuric bromide test paper to generate a yellow spot whose depth is compared with a series of standard arsenic spots to determine the arsenic content in the sample. This method is suitable for determining the content of arsenic in the range of 0.5～5 μg range of test solution.
4.8.2 Reagents and materials
4.8.2.1 Hydrochloric acid (GB/T622);
4.8.2.2 Arsenic-free zinc particles (GB/T2304); 29
GB 535—1995
4.8.2.3 Potassium iodide (GB/T1272) solution, 150g/L; 4.8.2.4 Stannous chloride (GB/T638), 400g/L hydrochloric acid solution; preparation method is the same as 4.7.2.4.
4.8.2.5 Arsenic standard solution, 0.100g/L; 1mL of this solution contains 100μg of arsenic.
4.8.2.6 Arsenic standard solution, 0.0025g/L; Pipette 25.0mL of arsenic standard solution (4.8.2.5) into a 1000mL volumetric flask, dilute to the mark with water, and mix well. This solution contains 2.5μg of arsenic in 1mL, and is prepared before use.
4.8.2.7 Lead acetate (HG/T3-974) cotton; 4.8.2.8 Mercuric bromide (GB/T1398) test paper; 4.8.3 Instruments and equipment
The glass container used for arsenic determination must be washed with concentrated sulfuric acid-potassium dichromate solution, then cleaned with water, and dried for use. General laboratory instruments and:
4.8.3.1 Arsenic analyzer
As shown in Figure 3, or other arsenic analyzers that have been proven by experiments to give the same results under the specified test conditions. 16.5
Figure 3 Fixture
Wide-mouth bottle or ground-mouth conical flask (1): volume 200mL; b. Rubber stopper or ground-mouth stopper (2);
c. Glass tube (3): 180mm long, 6.5mm in diameter at the top, with a hole of about 2mm in diameter at the end of the tube. Before use, fill the glass tube with lead acetate cotton, about 60mm high; d. Upper end of the glass tube (4): The surface of the upper end of the tube is ground flat, and there are 4 ear hooks below for fixing the glass cap; e. Glass cap (5): The bottom is ground flat, with a hole in the center that communicates with the glass tube, the hole diameter is 6.5mm, and there is a crescent-shaped groove on the top. When using, clamp the mercuric bromide test paper between the upper end of the glass tube (4) and the glass cap (5), and fix it with a rubber ring. 4.8.4 Analysis steps
4.8.4.1 Preparation of sample solution
GB535—1995
Weigh 10g of sample, accurate to 0.01g, and place it in a conical flask (1) (4.8.3.1a.), add 50mL of water, mix to completely dissolve, add 15mL of hydrochloric acid (4.8.2.1), and mix well.
4.8.4.2 Preparation of standard color scale
While preparing the test solution, according to Table 4, take the arsenic standard solution (4.8.2.6) and place it in 5 conical flasks (1), add water to 50mL, add 15mL of hydrochloric acid (4.8.2.1), and mix well. 4.8.4.3 Determination
Add 2mL of potassium iodide solution and 2mL of stannous chloride solution to each conical flask (1), mix well, and let stand for 15min. Table 4
Arsenic standard solution (4.8.2.6)
Corresponding arsenic content
Arsenic standard solution (4.8.2.6)
Place lead acetate cotton in a glass tube (3) (4.8.3.1c.) to absorb hydrogen sulfide. Corresponding arsenic content
Fix the mercuric bromide test paper, weigh 5g of zinc particles and place them in a conical flask (1), install the instrument according to Figure 3, and allow the reaction to proceed in the dark for 1~1.5h. Remove the mercuric bromide test paper, compare the color of the mercuric bromide test paper of the sample with the color scale of the arsenic standard solution series, and calculate the mass of arsenic in the sample. 4.8.5 Expression of analysis results
The content of arsenic (As) (α) is expressed as mass percentage (%) and is calculated according to formula (7): mo
×100=
m × 106
Wherein: mo—the mass of arsenic measured by comparison with the standard color scale, ug; the mass of the sample, g.
4.9 Determination of heavy metal content Visual turbidimetry 4.9.1 Summary of the method
m × 104
·(7)
In a weakly acidic medium (pH 3-4), the aqueous solution of hydrogen sulfide combines with the hydrogen sulfide in the test solution to form sulfides, which are then compared with the standard color scale of lead to determine the content of heavy metals (in terms of Pb). This method is applicable to test solutions with heavy metal (in terms of Pb) contents ranging from 15 to 100 pg.
4.9.2 Reagents and materials
4.9.2.1 Acetic acid (GB/T676) solution, c(CH,COOH)=1mol/L; Measure 58mL of acetic acid and dilute to 1000mL with water. 4.9.2.2 Saturated aqueous hydrogen sulfide solution
4.9.2.3 Lead standard solution, 0.1g/L;
This solution contains 100μg of lead per 1mL.
4.9.2.4 Lead standard solution, 0.01g/L; Pipette 10.0ml of lead standard solution (4.9.2.3) into a 100mL volumetric flask, dilute to the mark, and mix well. This solution contains 10μg of lead per 1mL and is prepared for use.
4.9.3 Instruments and equipment
General laboratory instruments and:
4.9.3.1 Colorimetric tube: 50mL, with ground glass cover. 4.9.4 Analysis steps
4.9.4.1 Preparation of sample solution5h. Remove the mercuric bromide test paper and compare the color of the mercuric bromide test paper of the sample with the color scale of the arsenic standard solution series to determine the mass of arsenic in the sample. 4.8.5 Expression of analysis results
Arsenic (As) content (α), expressed as mass percentage (%), is calculated according to formula (7): mo
×100=
m × 106
Where: mo—the mass of arsenic measured by comparison with the standard color scale, ug; the mass of the sample, g.
4.9 Determination of heavy metal content Visual turbidimetry 4.9.1 Method summary
m × 104
·(7)
In a weakly acidic medium (pH 3-4), the hydrogen sulfide aqueous solution combines with the hydrogen sulfide in the test solution to form sulfides, which are then compared with the standard color scale of lead to determine the content of heavy metals (in terms of Pb). This method is applicable to test solutions with heavy metal (Pb) content in the range of 15-100pg.
4.9.2 Reagents and materials
4.9.2.1 Acetic acid (GB/T676) solution, c(CH,COOH)=1mol/L; Measure 58mL of acetic acid and dilute to 1000mL with water. 4.9.2.2 Saturated aqueous hydrogen sulfide solution
4.9.2.3 Lead standard solution, 0.1g/L;
1ml of this solution contains 100μg of lead.
4.9.2.4 Lead standard solution, 0.01g/L; Pipette 10.0ml of lead standard solution (4.9.2.3) into a 100mL volumetric flask, dilute to the mark, and mix well. 1mL of this solution contains 10μg of lead and is prepared for use.
4.9.3 Instruments and equipment
General laboratory instruments and:
4.9.3.1 Colorimetric tube: 50mL, with ground glass cover. 4.9.4 Analysis steps
4.9.4.1 Preparation of sample solution5h. Remove the mercuric bromide test paper and compare the color of the mercuric bromide test paper of the sample with the color scale of the arsenic standard solution series to determine the mass of arsenic in the sample. 4.8.5 Expression of analysis results
Arsenic (As) content (α), expressed as mass percentage (%), is calculated according to formula (7): mo
×100=
m × 106
Where: mo—the mass of arsenic measured by comparison with the standard color scale, ug; the mass of the sample, g.
4.9 Determination of heavy metal content Visual turbidimetry 4.9.1 Method summary
m × 104
·(7)
In a weakly acidic medium (pH 3-4), the hydrogen sulfide aqueous solution combines with the hydrogen sulfide in the test solution to form sulfides, which are then compared with the standard color scale of lead to determine the content of heavy metals (in terms of Pb). This method is applicable to test solutions with heavy metal (Pb) content in the range of 15-100pg.
4.9.2 Reagents and materials
4.9.2.1 Acetic acid (GB/T676) solution, c(CH,COOH)=1mol/L; Measure 58mL of acetic acid and dilute to 1000mL with water. 4.9.2.2 Saturated aqueous hydrogen sulfide solution
4.9.2.3 Lead standard solution, 0.1g/L;
1ml of this solution contains 100μg of lead.
4.9.2.4 Lead standard solution, 0.01g/L; Pipette 10.0ml of lead standard solution (4.9.2.3) into a 100mL volumetric flask, dilute to the mark, and mix well. 1mL of this solution contains 10μg of lead and is prepared for use.
4.9.3 Instruments and equipment
General laboratory instruments and:
4.9.3.1 Colorimetric tube: 50mL, with ground glass cover. 4.9.4 Analysis steps
4.9.4.1 Preparation of sample solution
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