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HJ 479-2009 English PDF

HJ 479-2009_English: PDF (HJ479-2009)
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HJ 479-2009English339 Add to Cart 3 days [Need to translate] Ambient air. Determination of nitrogen oxides. N-(1-Naphthyl) ethylene diamine dihydrochloride spectrophotometric method Valid HJ 479-2009


BASIC DATA
Standard ID HJ 479-2009 (HJ479-2009)
Description (Translated English) Ambient air. Determination of nitrogen oxides. N-(1-Naphthyl) ethylene diamine dihydrochloride spectrophotometric method
Sector / Industry Environmental Protection Industry Standard
Classification of Chinese Standard Z15
Classification of International Standard 13.040
Word Count Estimation 13,166
Date of Issue 2009-09-27
Date of Implementation 2009-11-01
Older Standard (superseded by this standard) GB/T 15436-1995; GB/T 8969-1988
Drafting Organization Shenyang Municipal Environmental Monitoring Center Station
Administrative Organization Ministry of Environment Protection
Regulation (derived from) Department of Environmental Protection Notice No. 47 of 2009
Summary This standard specifies the determination of nitrogen oxides in ambient air spectrophotometry. This standard applies to the ambient air of nitrogen oxides, nitrogen dioxide, nitric oxide measurement.

Standards related to: HJ 479-2009

HJ 479-2009
Ambient air.Determination of nitrogen oxides.N-(1-Naphthyl) ethylene diamine dihydrochloride spectrophotometric method
HJ
National Environmental Protection Standard of the People's Republic
Replace GB/T 15436-1995 and GB 8969-88
Ambient air NOx (nitrogen monoxide and dioxide)
Determination of nitrogen - Naphthylethylenediamine spectrophotometric method
Ambient air-Determination of nitrogen oxides-N-(1-Naphthyl)ethylene
Diamine dihydrochloride spectrophotometric method
Published on.2009-09-27
2009-11-01 Implementation
Ministry of Environmental Protection released
Ministry of Environmental Protection
announcement
No. 47 of.2009
In order to implement the "Environmental Protection Law of the People's Republic of China", protect the environment, and protect human health, we now approve the measurement of water quality polycyclic aromatic hydrocarbons.
Eighteen standards, such as fixed liquid extraction and solid phase extraction high performance liquid chromatography, are national environmental protection standards and are released.
The standard name and number are as follows.
I. Determination of Polycyclic Aromatic Hydrocarbons by Liquid-Liquid Extraction and Solid Phase Extraction High Performance Liquid Chromatography (HJ 478-2009);
2. Determination of nitrous oxides (nitrogen oxides and nitrogen dioxide) - Determination of naphthalene diamine hydrochloride spectrophotometric method (HJ 479-
2009);
III. Determination of Fluoride in Ambient Air Filtration of Fluoride Ion Selective Electrode Method (HJ 480-2009);
IV. Determination of fluoride in ambient air Determination of fluoride ion-selective electrode method for lime filter paper (HJ 481-2009);
V. Determination of Sulfur Dioxide in Ambient Air - Formaldehyde Absorption - Pararosaniline Spectrophotometry (HJ 482-2009);
6. Determination of Sulfur Dioxide in Ambient Air - Tetrachloromercury Salt Absorption - Pararosaniline Spectrophotometry (HJ 483-2009);
VII. Determination of water content cyanide volumetric method and spectrophotometry (HJ 484-2009);
VIII. Determination of copper in water quality by diethyldithiocarbamate spectrophotometry (HJ 485-2009);
IX. Determination of copper in water quality 2,9-Dimethyl-1,10 phenanthroline spectrophotometry (HJ 486-2009);
X. Determination of Fluoride in Water Quality by Spectrophotometric Method of Zirconium Sulfate Sulfate (HJ 487-2009);
XI. Determination of Fluoride in Water Quality Fluorescence Spectrophotometry (HJ 488-2009);
XII. Determination of Silver in Water Quality 3,5-Br2-PADAP Spectrophotometry (HJ 489-2009);
XIII. Determination of Silver in Water Quality by Cadmium Reagent 2B Spectrophotometry (HJ 490-2009);
XIV. Determination of Total Chromium in Soils by Flame Atomic Absorption Spectrophotometry (HJ 491-2009);
15. Air Quality Vocabulary (HJ 492-2009);
XVI. Technical Regulations for the Preservation and Management of Water Quality Samples (HJ 493-2009);
17. Water Quality Sampling Technical Guidance (HJ 494-2009);
18. “Technical Guidance for the Design of Water Quality Sampling Plans” (HJ 495-2009).
The above standards have been implemented since November 1,.2009 and published by the China Environmental Science Press. The standard content can be found on the website of the Ministry of Environmental Protection.
From the date of implementation of the above standards, the following 20 national environmental protection standards approved and issued by the former National Environmental Protection Agency shall be abolished.
The exact name and number are as follows.
1. "Determination of six specific polycyclic aromatic hydrocarbons in water quality by high performance liquid chromatography" (GB 13198-91);
2. Determination of nitrogen oxides in air quality - Determination of naphthylethylenediamine hydrochloride (GB 8969-88);
3. "Saltzman method for determination of nitrogen oxides in ambient air" (GB/T 15436-1995);
4. Determination of the concentration of fluoride in ambient air, filter membrane and fluoride ion selective electrode method (GB/T 15434-1995);
V. Determination of Fluoride in Ambient Air Lime Filter Paper · Fluoride Ion Selective Electrode Method (GB/T 15433-1995);
6. Determination of Sulphur Dioxide in Ambient Air - Formaldehyde Absorption - Pararosaniline Spectrophotometry (GB/T 15262-94);
VII. Determination of Air Quality, Sulfur Dioxide, Tetrachloromercury Salt - Pararosaniline Hydrochloride Colorimetric Method (GB 8970-88);
VIII. Determination of Cyanide in Water Quality Part I Determination of Total Cyanide (GB 7486-87);
IX. Determination of Cyanide in Water Quality Part 2 Determination of Cyanide (GB 7487-87);
X. Determination of copper in water quality by diethyldithiocarbamate spectrophotometry (GB 7474-87);
XI. Determination of Copper in Water Quality 2,9-Dimethyl-1,10-phenanthroline Spectrophotometric Method (GB 7473-87);
Twelve, "Determination of Fluoride in Water Quality, Zirconium Sulfonic Acid Visual Colorimetric Method" (GB 7482-87);
XIII. Determination of Fluoride in Water Quality Fluorescence Spectrophotometry (GB 7483-87);
XIV. Determination of Silver in Water Quality, 3,5-Br2-PADAP Spectrophotometry (GB 11909-89);
Fifteen, "Measurement of mercury in water, cadmium reagent 2B spectrophotometry" (GB 11908-89);
XVI. Determination of Total Chromium in Soil Quality by Flame Atomic Absorption Spectrophotometry (GB/T 17137-1997);
17. Air Quality Vocabulary (GB 6919-86);
18. Technical Regulations for the Preservation and Management of Water Samples (GB 12999-91);
Nineteen, "Water Quality Sampling Technical Guidance" (GB 12998-91);
20. Technical Regulations for the Design of Water Quality Sampling Plans (GB 12997-91).
Special announcement.
September 27,.2009
Content
Foreword..iv
1 Scope..1
2 Terms and definitions.1
3 method principle..1
4 Reagents and materials.1
5 instruments and equipment. 2
6 interference and elimination. 2
7 samples.3
8 Analysis steps..4
9 results indicate ..4
10 Precision and Accuracy 5
Appendix A (Normative Appendix) Inspection of absorption bottles and determination of sampling efficiency..6
Appendix B (informative) Saltzman experimental coefficient determination 7
Foreword
In order to implement the Environmental Protection Law of the People's Republic of China and the Law of the People's Republic of China on the Prevention and Control of Atmospheric Pollution
This standard is established for human health and the determination of nitrogen oxides in ambient air.
This standard specifies methods for determining nitrogen oxides (nitrogen monoxide and nitrogen dioxide) in ambient air.
This standard is for the determination of air quality nitrogen oxides, naphthylamine diamine colorimetric method (GB 8969-88) and ambient air.
The determination of nitrogen oxides was carried out by the Saltzman method (GB/T 15436-1995).
"Determination of Air Quality Nitrogen Oxide Determination of Naphthylethylenediamine Hydrochloride" (GB 8969-88) was first published in 1988.
The quasi-drafting unit is the Beijing Environmental Monitoring Center; the first is the Salttzman Method for the Determination of Nitrogen Oxides in the Ambient Air (GB/T 15436-1995)
It was released in.1995, and the original standard drafting unit was the Shenyang Environmental Monitoring Center Station. This is the first revision.
The main revisions are as follows.
-- Revised the name and scope of the standard;
-- Improve the textual content of the standard method principle;
- Defining the amount of potassium permanganate and barium hydroxide used in the preparation of experimental water;
-- Increased interference and elimination clauses and sample retention terms;
- Refined the analysis steps and increased the blank test requirements;
-- Eliminated the second book "Soxidation" in the Saltzman Method for the Determination of Nitrogen Oxides in Environmental Air (GB/T 15436-1995)
Chromium-quartz sand oxidation method.
From the date of implementation of this standard, the national environmental protection standard “Air” approved and issued by the former National Environmental Protection Agency on March 26, 1988.
Determination of mass nitrogen oxides - Naphthylethylenediamine hydrochloride colorimetric method (GB 8969-88) and former National Environmental Protection Agency March 25,.1995
National Environmental Protection Standards for the Determination and Determination of Environmental Air Nitrogen Oxides by the National Standard for Environmental Protection (GB/T 15436-1995)
Abolished.
Appendix A of this standard is a normative appendix, and Appendix B is an informative appendix.
This standard was formulated by the Science and Technology Standards Department of the Ministry of Environmental Protection.
This standard is mainly drafted by. Shenyang Environmental Monitoring Center Station.
This standard was approved by the Ministry of Environmental Protection on September 27,.2009.
This standard has been implemented since November 1,.2009.
This standard is explained by the Ministry of Environmental Protection.
Iv
Determination of ambient air NOx (nitrogen monoxide and nitrogen dioxide)
Naphthylethylenediamine hydrochloride spectrophotometry
1 Scope of application
This standard specifies the spectrophotometric method for the determination of nitrogen oxides in ambient air.
This standard applies to the determination of nitrogen oxides, nitrogen dioxide and nitrogen monoxide in ambient air.
The method detection limit of this standard is 0.12 μg/10 ml of absorption liquid. When the total volume of the absorption liquid is 10 ml and the sampling volume is 24 L, it is empty.
The detection limit of nitrogen oxides in the gas is 0.005 mg/m3. When the total volume of the absorbent is 50 ml and the sampling volume is 288 L, the nitrogen oxides in the air
The detection limit was 0.003 mg/m3. When the total volume of the absorbent is 10 ml and the sampling volume is 12 to 24 L, the nitrogen oxides in the ambient air
The measurement range is from 0.020 to 2.5 mg/m3.
2 Terms and definitions
2.1 Nitrogen oxides
Refers to the oxide of nitrogen (as NO2) in the form of nitrogen monoxide and nitrogen dioxide in the air.
2.2 Saltzman experimental coefficient Saltzman-factor
The mixed gas for calibration of nitrogen dioxide prepared by the osmosis method, and the azo dye formed by absorption by the absorption liquid during gas production is equivalent to nitrous oxide
The ratio of the amount of acid to the total amount of nitrogen dioxide passing through the sampling system (see Appendix B for the determination method).
2.3 oxidation coefficient
Nitric oxide in the air is oxidized to nitrogen dioxide by an acidic potassium permanganate solution and is absorbed by the absorption liquid to form an azo dye.
The ratio of the amount of material to the total amount of nitric oxide passing through the sampling system.
3 Principle of the method
Nitrogen dioxide in the air is absorbed by the absorption liquid in the first absorption bottle in series and reacts to form a pink azo dye. One in the air
Nitric oxide does not react with the absorption liquid, and is oxidized to the nitrogen dioxide by the acidic potassium permanganate solution through the oxidation tube, and is connected in the second absorption bottle in series.
The absorption liquid absorbs and reacts to form a pink azo dye. The absorbance of the generated azo dye at a wavelength of 540 nm and the content of nitrogen dioxide
The amount is proportional. The absorbances of the samples in the first and second absorption bottles were measured, and the nitrogen dioxide and nitrogen monoxide in the two absorption bottles were calculated.
The mass concentration, the sum of the two is the mass concentration of nitrogen oxides (in terms of NO2).
4 reagents and materials
Unless otherwise stated, analytically pure reagents and nitrite-free distilled water in accordance with national or professional standards are used for analysis.
Sub-water or water of considerable purity. If necessary, experimental water can be added to 0.5 g of potassium permanganate (KMnO4) per liter of water in a full glass distiller.
And steamed with 0.5 g of barium hydroxide [Ba(OH)2].
4.1 Glacial acetic acid.
4.2 Hydroxylamine hydrochloride solution, ρ = 0.2 ~ 0.5 g/L.
4.3 sulfuric acid solution, c (1/2H2SO4) = 1 mol/L. take 15 ml of concentrated sulfuric acid (ρ20 = 1.84 g/ml), slowly added to 500 ml of water, stir
Evenly, cool for later use.
4.4 Acidic potassium permanganate solution, ρ (KMnO4)=25 g/L. Weigh 25g potassium permanganate in a 1 000 ml beaker and add 500 ml of water.
Slightly heat to dissolve all of them, then add 1 ml/L sulfuric acid solution (4.3) 500 ml, stir well, and store in a brown reagent bottle.
4.5 N-(1-Naphthyl)ethylenediamine hydrochloride stock solution, ρ (C10H7NH(CH2)2NH2·2HCl)=1.00 g/L. Weigh 0.50 g N-(1-naphthalene
Ethyldiamine hydrochloride in a 500 ml volumetric flask, diluted with water to dilute to the mark. This solution is stored in a closed brown bottle in the refrigerator
Refrigerated for stable storage for three months.
4.6 Coloring solution. Weigh 5.0 g of p-aminobenzenesulfonic acid [NH2C6H4SO3H] and dissolve it in about.200 ml of hot water of 40-50 °C to cool the solution.
At room temperature, transfer all into a 1 000 ml volumetric flask and add 50 ml of N-(1-naphthyl)ethylenediamine hydrochloride stock solution (4.5) and 50 ml.
Glacial acetic acid, diluted to the mark with water. This solution is stored in a closed brown bottle and stored in the dark at 25 ° C for three months. If solution
It is light red and should be discarded.
4.7 Absorbent. When using, mix the coloring solution (4.6) and water in a ratio of 4.1 (volume fraction), which is the absorption liquid. Absorbance of absorption liquid
The degree should be less than or equal to 0.005.
4.8 nitrite standard stock solution, ρ (NO2−)=250 μg/ml. accurately weigh 0.375 0 g sodium nitrite (NaNO2, excellent grade, use
It is dissolved in water before drying at 105 °C ± 5 °C), transferred to a 1 000 ml volumetric flask, and diluted to the mark with water. This solution is stored in a sealed brown bottle
Stored in the dark, it can be stored for three months.
4.9 Nitrite standard working solution, ρ (NO2−)=2.5 μg/ml. Accurately absorb nitrite standard stock solution (4.8) 1.00 ml in 100 ml
In a volumetric flask, dilute to the mark with water. Available now.
5 Instruments and equipment
5.1 Spectrophotometer.
5.2 Air sampler. The flow range is 0.1~1.0 L/min. When the sampling flow rate is 0.4 L/min, the relative error is less than ±5%.
5.3 Constant temperature, semi-automatic continuous air sampler. When the sampling flow rate is 0.2 L/min, the relative error is less than ±5%, and the temperature of the absorption liquid can be guaranteed.
Hold at 20 ° C ± 4 ° C. The sampling connection line is a borosilicate glass tube, a stainless steel tube, a Teflon tube or a silicone tube with an inner diameter of about 6 mm.
It may be shorter, no more than 2 m in any case, with a downward facing air inlet.
5.4 Absorbent bottle. A porous glass plate absorption bottle that can hold 10 ml, 25 ml or 50 ml of absorption liquid. The height of the liquid column is not less than 80 mm. Absorption bottle
The resistance of the glass plate, the uniformity of bubble dispersion and the sampling efficiency are checked in accordance with Appendix A of this standard. Figure 1 shows two porous glass plates that are more suitable.
Absorb the bottle. Use a brown absorbing bottle or a black hood for the absorbing bottle cover during sampling. New porous glass plate absorption bottle or porous glass after use
Plate absorption bottle, apply (1 1) HCl soak for more than 24 h, wash with water.
5.5 Oxidation bottle. A gas cylinder that can hold 5 ml, 10 ml or 50 ml acid potassium permanganate solution (4.4). The height of the liquid column should not be lower than 80 mm.
After use, the solution was washed with a hydroxylamine hydrochloride solution (4.2). Figure 2 shows two suitable oxidation bottles.
10 ml 50 ml
50 ml10 ml
Fig.1 Schematic diagram of the absorption bottle of the porous glass plateFig. 2 Schematic diagram of the oxidation bottle
6 interference and elimination
When the mass concentration of sulfur dioxide in the air is 30 times the mass concentration of nitrogen oxides, it negatively interferes with the determination of nitrogen dioxide.
Peroxyacetyl octoate (PAN) in the air produces positive interference with the determination of nitrogen dioxide.
When the concentration of ozone in the air exceeds 0.25 mg/m3, it negatively interferes with the determination of nitrogen dioxide. At the inlet end of the sampling bottle when sampling
Connect a length of 15 to 20 cm long silicone rubber tube to eliminate interference.
7 samples
7.1 Short time sampling (within 1 h)
Take two porous glass plate absorption bottles containing 10.0 ml of absorbing liquid and one oxygen containing 5-10 ml of acidic potassium permanganate solution (4.4)
To make the bottle (the height of the liquid column is not less than 80 mm), use the shortest silicone rubber tube to connect the oxidation bottle in series between the two absorption bottles (see Figure 3).
0.4 L/min flow rate 4~24 L.
7.2 Long time sampling (24 h)
Take two large porous glass plate absorption bottles and fill in 25.0 ml or 50.0 ml absorption liquid (4.7) (the liquid column height is not less than 80 mm).
Record the liquid level position. Take an oxidized bottle containing 50 ml of acidic potassium permanganate solution (4.4) and access the sampling system as shown in Figure 4.
The liquid is kept at a constant temperature of 20 °C ± 4 °C, and 288 L is produced at a flow rate of 0.2 L/min.
Note. When there is obvious precipitation in the oxidation tube, it should be replaced in time.
In general, an oxidizing bottle containing 50 ml of acidic potassium permanganate solution can be used for 15 to 20 days (sampled every other day).
During the sampling process, observe the color change of the absorption liquid to avoid penetration due to excessive mass concentration of nitrogen oxides.
7.3 Sampling requirements
The airtightness of the sampling system should be checked before sampling, and the flow calibration should be performed using a soap membrane flow meter. The relative error of the sample flow should be less than ± 5%.
Sunlight should be avoided during sample transport and storage during sampling. When the temperature exceeds 25 °C, transport for a long time (more than 8 h) and
Cooling measures should be taken when storing samples.
At the end of sampling, to prevent the solution from sucking up, close the water stop clip or electricity connected to the sampling system while the sampling pump stops pumping.
Magnetic valve (see Figure 3 or Figure 4).
Absorption bottle
Oxidized bottle
Absorption bottle
Silica gel dry bottle flowmeter
Gas pump
Water stop clip
Figure 3 Schematic diagram of manual sampling series
Absorption bottle
Oxidized bottle
Absorption bottle
Silica gel dry bottle flowmeter
Gas pump solenoid valve
Figure 4 Schematic diagram of continuous automatic sampling series
7.4 Field blank
The absorption bottle containing the absorption liquid is taken to the sampling site, stored under the same conditions as the sample, and transported until it is sent to the laboratory for analysis.
Care should be taken to prevent contamination during the transfer.
At least 2 field blank tests are required for each sample.
7.5 Storage of samples
Samples are collected, transported, and stored in the dark, and stored as soon as possible after sample collection. If it cannot be measured in time, the sample will be dark at low temperature.
Store at room, the sample is stored in the dark at 30 °C, stable for 8 h; stored in the dark at 20 °C, stable for 24 h; refrigerated at 0 ~ 4 ° C, at least
Stable for 3 days.
8 Analysis steps
8.1 Drawing of standard curves
Take 6 10 ml plug colorimetric tubes and prepare a series of nitrite standard solutions according to Table 1. According to Table 1, separately transfer the corresponding volume of nitrous oxide
Sodium standard working solution (4.9), add water to 2.00 ml, and add coloring solution (4.6) 8.00 ml.
Table 1 NO2− standard solution series
Pipe number 0 1 2 3 4 5
Standard working fluid (4.9)/ml 0.00 0.40 0.80 1.20 1.60 2.00
Water/ml 2.00 1.60 1.20 0.80 0.40 0.00
Coloring solution (4.6)/ml 8.00 8.00 8.00 8.00 8.00 8.00
NO2− mass concentration/(μg/ml) 0.00 0.10 0.20 0.30 0.40 0.50
Mix the tubes and place them in the dark for 20 min (room temperature is below 40 °C for more than 40 min), using a 10 mm cuvette at the wavelength
At 540 nm, the absorbance is measured with water as the reference. After subtracting the absorbance of the No. 0 tube, the mass concentration (μg/ml) corresponding to NO2− is used.
The regression equation of the standard curve is calculated by the small square method.
The slope of the standard curve is controlled at 0.960 to 0.978 absorbance·ml/μg, and the intercept is controlled between 0.000 and 0.005 (painted in 5 ml volume)
When the standard curve is prepared, the slope of the standard curve is controlled at 0.180 to 0.195 absorbance·ml/μg and the intercept is controlled to ±0.003).
8.2 Blank test
8.2.1 Laboratory blank test. Take unsampled blank absorbing solution in the laboratory, using a 10 mm cuvette at 540 nm.
The absorbance was measured using water as a reference. The laboratory blank absorbance A0 does not exceed ±15% under the conditions specified by the color development.
8.2.2 Field blank. Same as 8.2.1 Determination of absorbance. Compare the field blank with the measurement results of the laboratory blank, if the site is blank and real
The gap between the chambers is too large, find the cause, and resample.
8.3 Sample determination
After sampling for 20 min, leave it at room temperature below 20 °C for more than 40 min, and add the volume of the absorption liquid in the sample bottle to the mark with water.
Mix well. The absorbance of the blank sample was measured using a 10 mm cuvette at a wavelength of 540 nm with water as a reference.
If the absorbance of the sample exceeds the upper limit of the standard curve, dilute it with a laboratory blank test solution and measure the absorbance. But the dilution factor is not
It is greater than 6.
9 results indicate
9.1 Mass concentration of nitrogen dioxide in air
2NO
ρ (mg/m3) is calculated according to formula (1).
NO
( )AA a VD
Bf V
ρ − − × ×= × × (1)
9.2 Mass concentration of nitric oxide in air
NOρ (mg/m3) is calculated by the formula (2) based on nitrogen dioxide (NO2).
NO
( )AA a VD
Bf VK
ρ − − × ×= × × × (2)
NOρ' (mg/m3) is calculated by formula (3) based on nitric oxide (NO).
NO
NO
Ρρ ×' = (3)
9.3 The mass concentration of nitrogen oxides in the air NOxρ (mg/m3) is calculated by the formula (4) based on nitrogen dioxide (NO2).
2NO NO Nx O
ρ ρ ρ= (4)
In the above formulas. A1, A2--the absorbance of the sample in the first and second absorption bottles in series;
A0--the absorbance of the laboratory blank;
B--the slope of the standard curve, absorbance · ml/μg;
A--the intercept of the standard curve;
V--the volume of the absorption liquid for sampling, ml;
V0--sampled to the standard state (101.325 kPa, 273 K), L;
K--NO→NO2 oxidation coefficient, 0.68;
D--the dilution factor of the sample;
f--Saltzman experimental coefficient, 0.88 (w when the mass concentration of nitrogen dioxide in the air is higher than 0.72 mg/m3, f is 0.77).
10 Precision and accuracy
10.1 Determination of the precision and accuracy of NO2 standard gas
Five laboratories measured NO2 standard gas with a mass concentration ranging from 0.056 to 0.480 mg/m3, and the repeatability relative standard deviation was less than
10%, the relative error is less than ±8%.
10.2 Determination of the precision and accuracy of NO standard gases
Determination of NO standard gas with a mass concentration ranging from 0.057 to 0.396 mg/m3, the relative standard deviation of repeatability is less than 10%, relative error
The difference is less than ±10%.
Appendix A
(normative appendix)
Absorption bottle inspection and sampling efficiency determination
A.1 Glass plate resistance and micropore uniformity inspection
The new perforated glass plate absorption bottle is immersed for 24 hours or more with HCl (1 1) before being inspected and washed with water.
Each absorbing bottle should be measured for its glassboard resistance before use or after a period of use, and the uniformity of bubble dispersion after passing through the glass plate should be checked.
Absorbent bottles that do not meet the requirements for resistance and have uneven bubble dispersion should n......
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