GB/T 8021-2003 Determination of saponification value of petroleum products
Some standard content:
GB/T8021—2003
This standard is revised and uses the American Association for Materials Standard-M Method for Determination of Chemical Value of Petroleum Products. This standard is based on ASTM1200C and is re-issued.
For convenience, the corresponding clauses of this national standard and ASTM91-200 are listed in the information list:
In order to comply with the main requirements of this standard, these technical differences are directly marked in the blanks of the pages of the clauses involved. The main differences between this standard and ASTMD9420\ are as follows: Compared with method 4, the vibration test degree of the liquid in the groove is further increased. The determination liquid is said to be volatile;
… In method A, the determination is too strong. In order to eliminate the influence of air carbon dioxide, lean gas protection is used during the elimination. In the presence of a method, the titration is carried out in the form of a method: the hot acid 7 bomb can be used to titrate without adding a pre-protection. When the acid is replaced by ethyl acetate as a quantifier, the monoxide in the air can be hydrolyzed and the hydroxyl radical is consumed, which leads to a systematic error. For the convenience of use, the standard also makes the following modifications to eliminate the 4M-0 key energy interval:
The textual expressions of vertical reactivity and sub-presentability are modified according to the custom of our country, and the standard does not recommend G/180211S87 as the European production and chemical determination method. B/T30211S87 is not equivalent to using 150 625293.
Compared with GB18121S?Saponification constant determination method 3 of stone products, this standard has the following main changes: This method adds the "Method K electric treasure dropping method"
and in the titration process of method A, in order to "increase the intensity of the vibration in the bottle", the mixing tower is added to the liquid (3.1, 6.2 of GB15/18021-198, 8.1.9.3 of B/9321-2003). In the titration process of method 4, in order to eliminate the influence of carbon trioxide in the air on the titration, this method uses nitrogen protection during the titration (5.1.2 of GB/8021-198, 5.1.2 of GB/8021-2003). 200.1R1.1, 6.H.1) except for 7.2 of the original standard;
This standard adds the time and correction B
Appendix 4 and preparation of this standard are all research and development of the original standard proposed by Shizhou Tuo Chemical Industry. This standard is issued by China Petrochemical Research Institute Co., Ltd. The origin of this standard is China National Petroleum Corporation Limited, Lanzhou Research and Development Center: This standard is drafted by Gao Jun, Xue Yonghong, Zhou Yabin, and the standard version of this standard is: GB: 18021937.
1 Scope
Determination of saponification value of petroleum products
GD/T B021—2003
1.1 This standard is applicable to the determination of the content of saponifiable components in oil products (such as lubricating oils, additives, transmission parts, etc.) under test conditions: this standard includes two methods: Method A: Colorimetric Indicator Method (Chapter 11) and Method B: Potentiometric Titration (Chapter 12-Chapter 19).
1.2 Sulfur, phosphorus, fluorine compounds and some other chemical compounds in some petroleum products can also consume monomers or domains. Therefore, the determination results are not only largely determined by the existing saponifiable components in the product, but also affected by the above-mentioned external factors. For the saponification value determination results of petroleum products containing these compounds and internal combustion engine oils, crankcase oils and turbine oils, the external factors that affect the determination of these chemical values must be explained in detail.
The substances include organic acids, which are free of bacterial growth factors, and the majority of these substances are sensitive to the protein. The existence of these substances can be determined by the European method. The total chemical results of fats and fats can be determined to be higher than the normal value. In the process of titration, the "end point of the fluidization is avoided". The formula indicates that there are active compounds in the sample. When there are some single active compounds, sample elements and interfering substances in the sample, these substances will be significantly affected by the test. The limit of the test may be the most reliable basis for determining this chemical. 1.3 This standard only describes some special hazards related to the test process and does not mention all the problems. Therefore, use it! Before using a standard, appropriate safety and protection measures should be prepared and corresponding other management measures should be formulated. 2 Normative references
The clauses in the following documents become clauses of this standard through reference in this standard. The referenced documents from the date of the product, all subsequent amendments (excluding errors) or revisions are not applicable to this standard. However, if the parties reach an agreement on whether to use the latest version of the referenced documents, the latest version shall apply to this standard for all undated referenced documents: GB/4756 Sampling method for solid matter ((H/T47551998, ISO3173:1383) GB/T6682 Specification and test method for water used in analytical test laboratories (GB/T66821992, ISO3696:1987) SH0005 Solvent sleeve for oil industry
3 Terms and definitions
The following terms and definitions apply to this standard. 3.1
Saponification
The amount of fat dissolved in an alkaline solution to form aldehyde salts and alcohols. 3.2
Saponification value
The number of grams of hydrogen peroxide eliminated per 1% of the sample under test conditions. Note: The chemical values obtained in this standard are affected by the presence of other substances in the same mass. The above mentioned values are not included in the notes in 1.2. 4. Summary of the method
4.1 Place a sample in a suitable solvent, dimethyl ketone (methyl ketone), a serial solvent or a combination thereof, and heat with a certain amount of potassium hydroxide in ethanol. Titrate the excess alkali with a standard acid solution and calculate the chemical content. 1
GB/TB021—2003
4.2 The endpoint can be determined by the indicator method (method A) or the potentiometric method (method B). 5 Significance and use
5.1 Petroleum products contain some additives that can form metal soaps with oil, such as lipids. In addition, some used filter lubricants, especially used turbine oils and motor oils, also contain some compounds that can react similarly with oil. The saponification value refers to the amount of oil consumed when each sample is heated in a specific manner with oil. In this way, the amount of oil present in the sample can be estimated, that is, the free acid and complex acid (such as ester acid) that have been converted into metal soap under the desired addition conditions. 5.2 The saponification index is specified in the product specifications of lubricants and additives. Method A Color Indicator Method
6 Receivers and Equipment
6.1 Conical Flask and Condenser: A conical flask with a volume of 250mL or 300mL can be connected to a straight spherical reflux condenser: The conical condenser is tightly connected to the conical flask through a ground mouth. The spherical reflux condenser is loosely connected to the conical flask and can be breathable. The reflux water condenser can also be replaced by an air condenser.
Note: Do not use the wrong origin of the plan to observe the donation, solid to the chemical will be in the crazy or thin place hospital room, or glass bed delivery chemical hand washing, with examination flushing test (for warning... The acid will seriously hurt the body, is a carcinogen that has been recognized and is an egg before oxidation, and its neighbors will cause fire and have enough absorption, out of the amount can be used without comfort. The most similar will be rolled, 6.2 Water: Li liters or steam pure hot water bath, No. .3 dropper: 25 mL or 5C ml, fill with 0. 1 ml.6.4 Pipette: 25ml.:
6.5 Set volume new, 105 ml.:
7 Reagents and Materials
7.1 Reagents
Unless otherwise specified, all chemical reagents used in the experiment are analytical pure reagents. Water must meet the specifications of Grade 1 water in G3/T6682. 7.1.1 Ethanol: 95% ethanol, or anhydrous ethanol, the total volume of which is 9:1 with methanol. Note 11 Product Properties 2: 69% isocyanate can be used as a substitute for ethanol, but when the actual use is required, isocyanate can be used instead.
7.1.205m./L standard alcohol solution Use potassium hydroxide ethanol standard (see 7.1.5) to calibrate the starting time to the correct value. (M5/T.) When the saponification is less than 1:nKDH/g or the sample is used, in order to ensure the accuracy of the determination, add 3.5mxl/ml of light potassium hydroxide ethanol standard and 0.1mol/l of potassium hydroxide standard in the microplate. The corresponding C.1mol/l is used as the standard. 1,3D: chemically pure concentrate in a dark brown bottle. Note: The selected material is not dissolved in
7.1.4, 60:~·9u.
Xu: Of course, when it is absorbed,
7.1.5 Neutral phenolic acid indicator solution 1.1 Dissolve the above 1.1 enzyme in 1M 0.1% ethanol (see 3.1.). Prepare 1.5mol/l potassium hydroxide in ethanol by diluting with 0.1M potassium hydroxide in alcohol until it turns red, i.e. 0.5mol/l potassium hydroxide standard solution. Let the solution stand for 24h before use, and filter or siphon off the potassium hydroxide in ethanol. Use the potassium hydroxide standard solution to calibrate with the potassium hydroxide standard solution (see Note 2 and 7.1. of this specification). GB/T 8021-2003 Note 1. Alternatively, commercial potassium hydroxide (unspecified) 65% 6% ethanol with 0.5mol/l or 0.1mol/l potassium hydroxide standard solution can be used. This solution can be used to obtain the required air channel. Note 2: The precipitate of the above standard solution is very effective, so the temperature of the standard solution at the time of marking is close to that of the test solution.
7.1.70.1mol/L Potassium Hydrogen Formate Standard Solution: Put potassium hydrogen formate at 110°C and then accurately weigh 2.0422g of 0.0002 and put it into a 100ml volumetric flask, dissolve it with water, and heat it slightly to facilitate the screening. After cooling, dilute it to 100 with water.
7.1.8 Xylene.
Note: Extremely scarce, high risk of inhalation,
7.1.9 Solvent oil: meet the requirements of ST[0C05 7.2 Materials
Gas: Nitrogen, purity is about 99%,
8 Test steps
8.1 Blank test
8.1.! Each batch of samples (one or more) should be measured at the same time as the blank value. The measurement steps are as follows: use a full titration or a liquid titration to take 25 mL ± 0.03 mL of potassium hydroxide acetyl ester standard solution. Put it into a conical flask and fill it with 25 mL + 1 mL of ketone or other transportable solvent. Connect the condenser tube and the conical flask and heat it. The heating reflux time should be the same as the heating reflux time when measuring the sample: when the reflux is over, carefully add 0 mL of phenol (when using a spherical condenser, the condenser tube and the conical flask should be opened. When dripping, add a drop of neutral phenol to indicate full titration. In order to eliminate the change, put a piece of appropriate size in the environment and stir it in the falling liquid! Under the condition of nitrogen protection, use 0.5 mL/ml of ethylene glycol standard solution to heat the blank titration. No heating is required during the blank titration: Note 1: The following titration conditions can also be used. Titrant For D.5l/L, D.1n/T., the standard liquid is used. When the liquid is fully charged, no effective gas protection is added. However, when the liquid is charged, the salt standard liquid must be used, and high-pressure gas protection is added during the charging process. Note: For samples with very high requirements for the liquid, two air tests should be conducted and half of them should be averaged. When the standard test is required, only one air value needs to be determined. Note 1: When using the potassium hydroxide standard liquid to charge the liquid, the tip of the transfer tube needs to be inserted at 39 on the plate to ensure the discharge of the reduced gas. Note 1: The industry must check the cold development of the disease before the stay in the heat of the glass to the blood of the child's crack injection l oxygen reflux cup standard time needs 30 minutes, some patches can be self-decomposed within 10 minutes, safe, treatment, some special chemical research needs two hours to be able to be completely decomposed. Unless the relevant departments and visit a vote, the lung period or extended saponification time is not allowed, stop 6: after the start of the drug, add petroleum wake up not only quiet clear Ji Ling condensation reputation, but also cold Mix all the reactants. 7. Add 50ml of petroleum ether to the mixture. 8. The cation temperature should be 10-15 higher than the required temperature (the ketone temperature is 75>). The mixture should be shaken during the flow and can be transferred to a flask. 1.2 When the color of the indicator disappears, add a few more indicator. If the dye solution shows a shear color again as indicated before and after the indicator, continue to wait until the color disappears: add a few more indicator, and continue if necessary. When the color of the indicator disappears completely, add more indicator. When the color of the indicator disappears completely, it indicates that the titration end point has been reached. Record the value Y. When the titration end point is approaching, in order to ensure that the new titration end point occurs, add the indicator to ensure that the two are the same. 8.2 Sample preparation 8.2.1 Sampling GH/T4755 standard sampling. 2.2 The sample must be in a homogeneous state before determination. The test volume should be appropriately determined so that the amount of titrant used in the determination accounts for 40% to 80% of the amount consumed in the determination. The sample volume should not exceed 208. 8/TB021-2003 recommends the following sample volume: 8.3 Sample determination Electrochemical value/(mgK(H/g) 18:-- 400
111130
16--39
0~·15
Word sample/g
8.3.1 Weigh the sample from the small container into a conical flask, and add 25mL+1tnLJ enzyme or other optional solvents at a precision of 0.91%, then accurately measure 2% ml. 0.03mL potassium hydroxide ethanol standard solution with a fixed tube or pipette and inject it. 8.3.2 For those new oils or additives that are difficult to concentrate, 15mL--25mL of solvent or distillation should be added before adding ketone.
8.3.3 Connect the condenser and the flask and heat them. When reflux begins, continue heating for 30 min (see Note 8.1.1), then immediately remove 5) 111. Carefully add the petroleum ester to the inner wall of the condenser (see Note 7 in 3.1.1) (Note - do not pour it on the water. If a pre-cooling is used, slightly open the interface between the condenser and the flask before the aldehyde is tested. B.3.4 Add 3 drops of neutral phenol to the sample in the cone filter: In order to increase the density, place a suitable size of stirring bottle into the dense liquid. Then, titrate with 3.5 mol/L hydrochloric acid standard solution under hydrogen protection (no heating is required). When the color of the indicator disappears, add a few drops of indicator. If the solution shows the required color after adding the indicator, wait until the color disappears and add a few drops of indicator. If necessary, continue titrating to the endpoint. When the indicator color disappears completely and the sieve does not show the color after adding the indicator, the titration has reached the full point. The amount of indicator consumed at this time is calculated as V:. When measuring a wax sample, in order to prevent the sample from being inhibited during the titration, if necessary, more solution can be added. 9 Calculation
9.1 Sample electrochemical value A (mgK0H/g) is calculated by formula (1): A - 56.1-cV-V.1/m
Where:
Concentration of salt standard solution ml/L
Mass of potassium hydroxide/ml
Volume of hydrochloric acid standard solution consumed in the given air, V
Volume of salt standard solution eliminated by the given sample, m1. Sample quantity
10 Report
10.1 For samples with electrochemical values less than 5nmgKOH/g, report the results to the nearest 0.5mgKOH/g. 10.2 For samples with electrochemical values greater than or equal to 50mgKOH/g, report the results to the nearest integer. 10.3 For dry electrical paint, the results shall be reported to an accuracy of 0.1 g KOH/R. 10.4 When reporting chemical values, the reference method shall be stated, such as Method A of GB/T 8021. 11 Precision and bias
11.1 Density
The reliability of the determination results shall be determined as shown in Figure 1 (95% confidence level). -(1)
Note: In Figure 1, there is a small amount of color in the new oil, the door oil or the oil that darkens during the internalization process. The state of the dark oil will be determined at a high fixed point. For the ten types of oil samples, the potentiometric titration method (Method B1) can be used. Gram
GB/7 8021--2003
When the same operator and the same instrument are used to measure the same test group under the same test conditions, the difference between the two independent results shall not exceed the data shown in Figure 1. 11.1.2 When different operators measure the same sample at different test rates, the difference between the two independent results shall not exceed the data shown in Figure 1.
11.2 Deviation
In the previous test method, the workmanship is not The results can be compared with the scientific research results of the service. Therefore, there is no evidence that the deviation of this method is sufficient for this method. Precision range GB/T8021-2003 12 Instruments and equipment Method B- Potentiometric titration 12.1 Conical flask and instrument: Alkali-resistant conical flask with a volume of 25mT.-30mT. can be connected to a conical reflux tube. The point condenser can be tightly connected to the dimensional flask through grinding, and the spherical condenser can be loosely connected to the flask. At the same time, the water condenser can be replaced by an air condenser. 12.2. Water, use electric or steam to heat the appropriate water. 12.3 Manual filter and automatic recording electrostatic titration instrument. 12.4 Electrode: High quality electrode must be used. Combined electrode or suitable glass electrode and image electrode can be used. Silver/saturated integrated chain enzyme reduction or ionization electrode with energy and potassium chloride solution can be used. Cleaning and maintenance of the electrode is essential.
12.5 Beaker, 250mL or 300ml.
Note: Unless the electrode is combined, the potential cannot be reversed in the same shape bottle. The small-mouthed capacitor is used to maintain the shape. 12.6 Stirrer, titrator, titration: The typical plastic potentiometric titration cell assembly method is as shown in the following figure. Ruby electric cabinet set
also like the day
sand shoulder side treatment
Figure 2 Potentiometric titration cell
I need electric night research
de-ring kettle (Chemical material)
C electric camera (must be able to)
wind ring
force explosion medium type extraction
(behind the fixed tube)
12.6.1 adjustable speed agitator: as a force agitator or electric agitator, the part must be chemical stove. When the electric agitator is used: it must be connected to eliminate the influence of the part that is not connected to the motor on the reading during the setting process. When encountering this situation, it is best to use a magnetic agitator.
12.6.2 Titration, 10ml. to 23ml.. divided into 0.05mL, the volume is +C.2mL, or choose an automatic burette with a corresponding volume.
12.6.3 Titration table: can place beakers, electrodes and burettes, and will not touch the reagent electrode, burette or stirring fuel when moving or lifting the beaker.
GB/T 8021—2003
Work: Some products are pushed down by the electrostatic field. When the titration device (beaker and electrode) is moved closer, you can see that the pointer of the titrator does not move normally. In order to prevent this, you can use an ungrounded copper mesh on the top, or a screen, 12.7 magnetic stirring sample, because in the process of full determination, two phases will flow in parallel to release potassium chloride, so the stirring conditions are very important: therefore, vigorous stirring is very necessary,
Outline: If you only use a small pressure, a low pressure will be enough. If you use a small pressure, now use the highest The degree of the test cannot fully simulate the partial selection of children. The most suitable two-dimensional shape can be stirred with a slurry.
13 Reagents
Unless otherwise specified, all reagents used in the test are analytically pure reagents. The water is in accordance with the specification of first-class water in GB/T662. 13.1 Alcohol, 5% ethanol, or a mixture of 95% ethanol and methanol (volume ratio is 9:1) 13.2 0.5mol)/I. Hydrochloric acid standard: use potassium hydroxide 7. Alcohol standard solution and standardize (see 7.1.2 half 13.6) when standardizing, the accuracy is 0.0005mol/L| |tt||13.3 Butanone: Chemical, packed in dark or brown bottles.13.4 Oil-free ~℃
13.5C,5mn:/L Potassium hydroxide in alcohol standard solution: Prepare 0.5mal/L potassium hydroxide in ethanol with ethanol. Store this solution in a dark place at 245°C before use and filter or light it. You can use a commercial potassium hydroxide sample (no brand name) and $55 ethanol to mix and prepare 0.5mol/T. or 0.12ol/[. Potassium hydroxide in 7.5mol/L alcohol standard solution. This special filter chain can reach the specified value (in addition, 3,1.6, discuss 2), potassium hydroxide The ethanol solution is calibrated with potassium hydrogen phthalate standard solution (see Note 2 of 7.1.6 and 13.6). 13.6C.1ml/1. Potassium hydrogen phthalate is difficult to dissolve: Dry potassium hydrogen phthalate at -1D℃ ±5: for 1 year, then accurately weigh 2.0422R=0.0002g and put it into a 120ml volumetric flask, dissolve it with water, and slightly heat it if necessary to promote dissolution. After cooling, dilute it with water to 100ml.
13.73.0lol/L potassium hydroxide solution: Prepare with water and 225.2g potassium chloride or 1.01. Dissolve. 13. 8 Trimethylbenzene.
13.9 Dai Cui,
13.10 Special cat: Meet the requirements of 5H0005. 14 Preparation, inspection and maintenance of the electrode system 14.1 Electrode specifications
14.1.1 If you want to change the mercury electrode inner filter from a non-aqueous salt bridge to an aqueous salt bridge, first drain the aqueous solution, wash the electrode with water and methanol (or light aqueous alcohol), then wash the outer tube (salt bridge) with 0.1% potassium chloride electrolyte for several times, and finally, fill the electrode with 3.0mol/L potassium amine aqueous solution from the injection port. 14.1.2 If the state transformer tube loss, first carefully loosen the drum cover kidney, thoroughly touch the silicon surface of the test transformer, then loosen the cover base relatively loosely, and drip a few drops of electrolyte on it to completely moisten the entire tube. When not in use, fill the calomel electrode with ma1/1 potassium hydroxide solution, plug the injection port with a stopper, and then insert the mercury electrode and the glass electrode into the beaker filled with water. In the end, keep the electrolyte surface high and the filter screen in the calomel electrode slowly dry. 14.2 Electrode testing: new electrodes or electrodes that have been used for one year should be calibrated with 0.Emol/L acetic acid standard and 1 cm1 C.5 mrl/L potassium hydroxide standard. 14.3 Electrode protection 14.3.1 During the period of use, the electrodes should be cleaned with chromic acid cleaning solution or non-chromic acid cleaning solution at least once a week. GB/T B021—2003 14.3.2 The 5.0tmol/L potassium oxide solution in the electrode should be replaced and recharged at least once a week. Each time the solution is recharged, ensure that there are potassium oxide crystals in the solution. At all times, the electrolyte in the electrode must be kept pressed against the filter surface of the titration cup. 14.3.3 When not in use, place the lower half of the electrode into a beaker filled with water. When there is a long time between two consecutive titrations, the electrode must not be left in the titration cup. 14.3.4 At the end of a full blank and between two consecutive titrations, there will be a thin layer of potassium oxide crystals on the electrode and the burette tip. At this time, you can use a plastic cleaner filled with water to remove the potassium oxide and insert the electrode into a beaker of water to rinse for 10 minutes. Then use filter paper to absorb the water on the electrode surface, but do not wipe the electrode. 14.3.5 After the continuous equilibration of a batch of samples, there will be a mixture of potassium oxide crystals and sample particles on the electrode and the titration tip. At this time, you can wash the electrode and the burette tip in a beaker containing the following solvent: ml. of solvent oil:
38mL of isopropyl alcohol,
ml of water
Stir for a long enough time (at least 5 inches) to completely dissolve the substances, and rinse off the remaining detergent with water. Then insert the electrode into the beaker of water and rinse for a few seconds. Then use a replacement to absorb the water on the surface of the electrode, but do not wipe the electrode. 14.3. The product electrode must be firmly fixed in the bracket to prevent the electrodes from moving during the positive and negative electrodes. The movement of the electrode will cause electronic noise, which will lead to the detection of the target endpoint and reduce the complexity of the target result. 15 Test procedures
15.1 Blank test
15.1.1 Each sample or sample (one or more) (see Note 2 in 3.1.1) shall be tested simultaneously with the blank value. The test procedures are as follows: Use a burette or pipette (see Note 3 in 8.1.1) to accurately take 25 ml. = 0.031 ml. of potassium hydroxide ethanol standard drop into a flask, and add 25 mL ± 1 mL of butanone or other selected quencher. Connect the condenser and conical flask and heat it (see Note 8 in R.1.1). After heating for 3 minutes from the beginning of reflux (see Note 8.1), immediately pour 10 mL of white extract (6.1.7) carefully along the inner wall of the conical flask. Be very careful to prevent the petroleum ether from rushing out of the condenser (when using a spherical condenser, keep the interface between the condenser and the conical flask loose), then heat (do not heat with a door) and perform potentiometric titration with 0.1\01/1.0 standard salt solution. 15.1.2 Fill the conical flask with 15 mL of non-oily aldehyde solution and pour the washing solution into the beaker. 15.1.3. Place a sample in a cup containing a clear solution. After the solution is stirred, close the pressure switch, insert the sample into the solution and stir the sample as much as possible. Adjust the rotation so that it is as large as possible without generating gas pools and solution waves. 15.1.4. In the titration, use 0.Emol/L hydrochloric acid standard solution to titrate the sample in a 2mT/min increment. There are two inflection points corresponding to the equivalence point, one is the inflection point of free potassium hydroxide (calculated as V in 17.1, and the other is the inflection point of potassium hydroxide contained in a small amount of potassium hydroxide on the market and the potassium dioxide dust dissolved and absorbed in the air during the titration (Figure 3). 15.T.5. At the beginning of the titration, a certain amount of titration can be added to speed up the titration process. 15.2. Sample preparation
The sample must be in a homogeneous state before titration. When selecting a sample pan, make the test tube consume The amount of the saturating agent shall account for 40% to 0% of the agreed amount of the blank saturating agent, but the amount of the sample shall not exceed 208 (see 8.2.2). 15.3 Sample determination 15.3.1 Weigh the sample from a small beaker into a beaker, calibrate to 0.1&, add mL-1㎡ tantalum or other optional buffer, and then use a lubricating tube or a grid tube (see 8.1.2 Note 5) to accurately measure 25ml. ± 0.05ml. Potassium hydroxide alcohol standard drop tablets into it. 15.3.2 For those samples that are difficult to dissolve, such as lubricating oil or saturated oil, add 15mL-25mL of the saturating agent 8 before adding the tantalum, GB/T 8021—2003
15.3.3 Connect the condenser and the conical flask and heat them. When reflux begins, continue heating for 30 minutes (see 4 and 5 in 8.1.1). Immediately after heating, carefully pour the remaining petroleum aldehyde into the conical flask along the inner wall of the condenser (warning: do not pour the petroleum aldehyde into the water bath). If a bulb condenser is used, loosen the joint between the condenser and the conical plate before adding the petroleum aldehyde. 15. 3.4 Titrate the above solution with 0.5 mol/L standard solution (no further heating is required). Blank titration procedure is the same as the blank titration procedure (see 15.1). Figure 3 shows a complete sample titration curve. The difference between sample titration and blank titration is that blank titration does not require two additions. In addition, the titration conditions are not too harsh. 15.3.4.1 The potential reading is relatively stable. Before the addition of titrant, the potential is about -520m V, the first mean point is sharp, out of specification around 3UV, the second inflection point is very sharp, now around 50mV. - So
D || ... |Oxygen oxide does not contain any sodium hydroxide.
It is not affected by the oxidation in the air.
Figure 3 Potentiometric titration curve
16.1 The method of preparing samples by measuring oxygen quality should ensure the accuracy of the determination method. The samples with high sensitivity should be selected as much as possible for testing:
16.2 Before using this standard, users should determine the average value and upper and lower limits of the oxidation value of the quality control samples through actual measurement. 16.3 Use quality control charts and other statistical comparison methods to record and analyze the quality control data to obtain the quality control data of the entire test process. Any abnormal quality control number should be investigated and the root cause should be determined promptly. The conclusion of this investigation should be quickly followed by the user of the standard to correct the entire test process.
16.4 The frequency of quality control evaluation depends on the rigor of the test, the stability of the test process and the customer's safety needs: Generally, quality control samples must be analyzed in each test work. If a large number of samples need to be analyzed regularly, the frequency of quality control evaluation must be increased. However, when the test results are within the control range, the quality control test can be reduced accordingly: according to the precision of this method, the quality control test data should be checked regularly to ensure the quality of the test data. 16.5 As far as possible, select those samples that can represent the daily test as the companion samples for the quality control test: During the planned test period, sufficient quality control samples must be provided, and these samples must be properly stored under the following conditions: 17 Calculation 17.1 The chemical value A (mgKH/g) of the sample is calculated according to formula (2): A: 56. lz(Vg-Vg>/m
In the play:
56.1——The mass of potassium fluoride, 1/10The density of hydrochloric acid standard solution, rnl/[.,
V——The volume of acid standard solution consumed by titration blank. ILThe volume of saline standard solution consumed by titration sample, mL: The maximum volume of sample, g
17.2The first inflection point is the equivalence point of hydrogen ions, so it is confirmed as the titration end point. If the potassium hydroxide contains sensitive salt contaminants or the solution absorbs the carbon dioxide blanket in the air during the titration process, a second inflection point will appear (see Figure 3): If this is found, the next inflection point is used as the blank titration end point and the sample full titration point. V. 18 Report
18.1 For samples with saponification values less than 50 mgKOH/g, the reported results shall be accurate to 0.5 mgKOH/g. 18.2 For test peaks with saponification values greater than or equal to 50 mgKOH/g, the reported results shall be accurate to the nearest integer. TS.3 For electrical insulation oils, the reported results shall be accurate to 1.1 mgKOH/g. 18.4 When reporting saponification values, the reference method shall be indicated: e.g., GB/T 8021. 19 Precision width and deviation
19.1 Precision width
The accuracy of the results shall be 95% as specified below. Two results shall be obtained by one operator using the same instrument and under the same test conditions for the same test weight. 19.1. 1 Repeatability
The difference between the results is no more than 2.76mRKH/8
19, 1.2 Reproducibility
The operator in different laboratories measured the same sample, and the results of two independent results were not more than 1n.4mRKOH/g.
19.2 Deviation
This method is a test method, and there is no reference material for comparison, so there is no error data for the original test method.
Appendix A
(Stealing Records
About CB/T8021 Analysis Tips
The following is helpful information when using this standard for testing, but it can never replace this standard. GB/T 8021—2003
九1. Do not use round bottles with scratches or large marks, because potassium hydroxide is more likely to react with them. The round bottles should be cleaned with cold chromic acid cleaning solution or other non-chromium oxidizing cleaning agents. A.2 Use potassium hydroxide acetic acid standard drop to calibrate the salt solution, and the concentration of 0.0005 mol/L can be measured. A.3 Use potassium hydrogen phthalate solution to calibrate potassium hydroxide ethanol solution. A4 After the expiration date, potassium hydroxide will change color. In this case, it should be discarded. A better method is to prepare potassium hydroxide solution with potassium hydroxide solution. The blank value of this solution is more stable because it does not contain salts, so it does not produce complex inflection points. A.6 When the electrochemical value of the sample is less than 1mKOH/, use 0.1mol/1.5KOH solution and salt solution instead of 0.5mol/L potassium hydroxide solution and salt solution. This will make the determination more accurate. A7 The measured room value is applicable to all samples to be tested at the same time. A. The daily method recommends weighing the mother sample, but do not exceed the upper limit of 20g. A.9 The saponification time of a sample may be a little longer than 0min. For samples with known saponification time, the best saponification time should be determined. A.10 For samples with different colors or dark colors, it is better to use potentiometric titration rather than color indicator method, because potentiometric titration is very sensitive to indicate the end point.
A.11 During the determination process: Since the samples are miscible and potassium chloride precipitation is formed, the stirring conditions are very important, so strong stirring is very necessary. Stirring with tetraethylene. A.12 When the operator is close to the test, if the pointer moves back and forth unsteadily, the instrument should be shielded. 4.13 The electrode should be cleaned and foreign matter on the annular sleeve of the electrode should be removed. Regular calibration of the electrode is very important to obtain repeatable potential values. bZxz.net
A.14 Between blank titration and two adjacent determinations, a thin film of potassium chloride will be deposited on the electrode tip. This should be washed off with water.
A.15 Use paper towel to absorb the water on the electrode, but do not wipe it. A. 16 After each batch of titration, wash the electrode with water to remove the chemical and sample residue on the electrode surface, then soak the electrode in a solution of 59mL of oil, 38mL of isocyanate and 38mL of water for about 1 minute. After heating, further wash the electrode with water and dry it with filter paper.
A. 17 During the titration process, the electrode must be fixed halfway on the bracket. The electronic noise generated when the electrode moves will affect the repeatability of the results.
A. 18 If there is a small amount of potassium carbonate in the potassium hydroxide solution, and the solution absorbs carbon dioxide in the air to generate potassium carbonate during the titration process, it will produce two inflection points on the potentiometric titration curve. The first inflection point indicates potassium hydroxide, and the tenth inflection point indicates potassium carbonate. A.19 Saponification value cannot be converted by total acid value. Sometimes the calculation will make the actual saponification value higher. This is because some alkali products produce alcohol ions during hydrolysis.
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