Chemical laboratory technician questions and answers
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1. What is the temperature range of the E-201 composite electrode? Answer: 5--60°C, but when measuring above or below room temperature, temperature correction must be performed, otherwise the sample will be cooled (heated) to room temperature and then measured. 2. What is the pressure of the vacuum drying oven? Answer: The pressure of the vacuum drying oven used to test the solid content of PS is 0.1Mpa, and then the temperature is maintained at 200±5°C for 10 minutes. 3. What are the factors that affect the absorbance value of the solution? Answer 1) The sample is not filtered (2) The zero point of the instrument is not calibrated (3) The cuvette is dirty (4) The selected wavelength is wrong 4. The electrode lead of the pH meter is dirty, what will be the result? Answer: The electrode lead is not clean, making the measurement unstable. 5. What should you pay attention to when using a trace water meter to measure samples? Answer 1) Check whether the instrument is stable and whether "stable" appears (2) Check whether the residual liquid in the bottle exceeds the mark (3) Whether the desiccant has expired (4) During the weighing process, the pinhole should be blocked with a rubber pad to prevent the sample from evaporating. 6. I don’t know the conductivity range of the solution being measured. How to deal with it? Answer: You should first move the range selector switch to the maximum position for measurement, and then gradually downshift to prevent the meter needle from bending. 7. What is the difference between using a platinum black electrode and a platinum bright electrode? Answer: If the conductivity of the solution being measured is lower than 10us/cm, use platinum bright electrode DJS-1. If it is above 10us/cm, use platinum black electrode DJS-10. .8. What should I do if the conductivity of the measured solution is greater than 10 μm/cm and the DJS-1 type platinum bright electrode cannot measure it? Answer: DJS-10 type platinum black electrode should be used, adjust the electrode constant compensator to 1/10 of the matching electrode constant, and then multiply the measured conductivity by 10 to get the measured value. 9. How to change the wavelength of the λ-11 spectrophotometer? Answer: Press GO TO After pressing the key, enter the wavelength value and press the ENTER key to confirm, which will become the replaced wavelength. 10. What to do if the capillary part of the viscosity tube has a cutoff phenomenon during the test? Answer: Treat the inside of the viscosity tube with concentrated sulfuric acid, and then rinse with methanol. 11. Under what circumstances does the pH meter need to be calibrated in advance? Answer: There is a large change in the solution temperature and the temperature during calibration, the electrode has been dried for too long, the new electrode has been replaced, and the measurement Measure overly concentrated acids and bases, and measure relatively concentrated organic solvents. 12. What is the basis for the reagents used to calibrate the zero point of the spectrophotometer? Answer: It is selected based on the solvent in which the sample is dissolved or diluted, and the absorbance value of the reagent is eliminated. 13. What is the name of the instrument used to analyze the turbidity value of latex? What is the wavelength? How big is the cuvette? Answer: Use a spectrophotometer, wavelength 700nm, cuvette 1cm. 14. What is the situation of MB200 in the running state? A: The power New Sample Run light is on. 15. What items are displayed after the analysis of the instrument MB200? A: Moisture content (%), solid content (%), initial sample weight, final sample weight 16. Briefly describe the principle of polymerization measurement in styrene? A: The styrene polymer present in styrene monomer is insoluble in methanol, so dry methanol is added to the styrene sample. The content of the polymer can be determined by measuring its turbidity. 17. What is the purpose of adding polymerization inhibitors to styrene products? Answer: To reduce the polymerization loss of styrene monomers and prevent equipment clogging and product polymerization during transportation. 18. When the polymer content in styrene products exceeds 15mg/kg (ppm), how should it be diluted? Answer: Use a pipette to take 20mL of the sample from the prepared sample and put it into a 50mL volumetric flask. Dilute with n-hexane to the mark and measure. If the polymer content is still high, continue dilution. 19. Describe the principle of measuring the content of polymerization inhibitor (p-tert-butylcatechol) in styrene? Answer: Extract styrene with sodium hydroxide aqueous solution, separate the water layer containing TBC (converted into a colored quinone structure), and then compare Color determination. 20. What are the reasons that affect the high solid content value? What are the treatment measures? Answer 1) The temperature of the oven (muffle furnace) does not reach the set value, start drying (see if the temperature does not reach the set value, put it in the oven or muffle furnace) (2) The baking time is not enough (according to the specified time) (3) The sample taken is uneven (replace it several times before taking it) (4) The sample was taken out for too long (weigh it immediately after cooling to room temperature) 21. When analyzing NaOH, if the titration end point is accidentally exceeded, should the result be high or low? Answer: According to the formula W%=0.04VM/m, the volume is too large at this time and the result is too high. 22. When measuring the IV value, why is methanol solution added to the latex sample processing? Answer: At this time, the solution can be uniform and fully mixed. 23. What is the PH value? Answer: The H value is the negative logarithm of the hydrogen ion concentration in water, which represents the pH of the solution. 24. What is the principle of pH value measurement?|Answer: An electrode composed of an indicator electrode and a reference electrode is inserted into the solution to form a galvanic cell. At room temperature (25°C), each unit of pH value is equivalent to an electromotive force change value of 59.1mv, which is directly expressed as a PH reading on the instrument. The temperature difference is equipped with a compensation device on the instrument. 25. What are the first aid measures for methanol poisoning? Answer: If the skin is contaminated, rinse it with clean water. If it splashes into the eyes, rinse with 2% NaHCO3 immediately. If ingested, immediately use 3% NaHCO3 solution to fully lavage the stomach and consult a doctor. 26. What are the poisoning effects and symptoms of methanol? Answer: Steam poisoning by inhalation can also be absorbed through the skin. Acute: neurasthenia, blurred vision, poisoning symptoms, chronic, neurasthenia, weakened vision, eye pain, If swallowed, 15mL can cause blindness, and 70-100mL can cause death. 27. Please tell me which chemicals are analyzed in the ABS grafting section? Answer: Potassium persulfate, emulsifier (N-70) and SN-10028. What are the conceptual differences between density and specific gravity? Answer: Unit: Density g/cm3 Specific gravity is 20℃ The ratio of the mass per unit volume of the product to the mass of pure water per unit volume at 4°C 29. What is the significance of measuring PH? Answer: Measuring the PH of latex and chemical agents reflects that the concentration of hydrogen ions has an impact on the stability of the agent and participation in the reaction. It is a performance index for evaluating latex. 30. Why is stirring required for the measurement of total aldehyde content in styrene? 1 hours? Answer: Because the reaction between hydroxylamine hydrochloride and the total aldehydes in styrene is an organic reaction, and the organic reaction is slow, it needs to be stirred for 1 hour to speed up the reaction. 31. When preparing a 2% methanol solution of hydroxylamine hydrochloride, why use thymol blue as the indicator and neutralize it with acid or alkali until it turns orange? Answer: Because the methanol solution contains trace amounts of acid or alkali and aldehydes, in order to eliminate reagent errors, thymol blue is used as the indicator, and alkali or acid is used to neutralize to orange. 32. Describe the principle of the method for determining the total aldehyde content in styrene? Answer: The methanol solution of hydroxylamine hydrochloride reacts with the active aldehydes in the styrene sample, and the amount of hydrochloric acid generated is equivalent to the amount of aldehydes in the sample. The generated hydrochloric acid is titrated to the end point with a sodium hydroxide standard solution. Using thymol blue as an indicator, the corresponding total aldehyde content in the sample can be calculated based on the volume of the sodium hydroxide standard solution consumed. 33. What is a blank test? Answer: It is a test that is performed according to the analysis steps and conditions of the sample without adding a sample. 34. How many categories can the titration analysis method be divided into? What are they? What titration method does the analysis of total aldehyde content in styrene belong to? Answer: Divided into four categories, (1) Acid-base titration method (2) Oxidation-reduction titration method (3) Precipitation titration method (4) Coordination (complexation) titration method The analysis of total aldehyde content in styrene belongs to the acid-base titration method 35. When measuring TBC in styrene, why does the extract need to be filtered with filter paper? What are the effects of not filtering? ` Answer: It is to filter out trace amounts of polymers and a small amount of impurities in the extraction solution to avoid affecting the measurement results. Failure to filter will make the analysis results higher. 36. How to judge the expiration of the electrolyte? Answer: The water content of the measured sample is significantly reduced, and the titration time is too long. 37. Why measure the water of carbohydrates (water in benzene)? Answer: Too much water in benzene destroys the structure of the catalyst in the post-processing system, reduces the activity of the catalyst, and shortens the service life of the catalyst. 38. What is the unit of conductivity? Answer: Siemens, 1S/cm=10~3ms/cm=10~6us/cm. 39. What are the common pH buffer solutions? Answer: There are three types: 4.01, 7.00, and 10.00. 40. When doing IV value, what is the purpose of cleaning the viscosity tube with DMF? Answer: Use DFM to clean it repeatedly to eliminate the moisture in the viscosity tube. 41. In TB analysis, why is evaporation used? When distilled water is fixed to volume, should it be added to 3/4 of the volume of the volumetric flask without directly adding it to the scale? Answer: After initial mixing, add to the scale to avoid volume changes after mixing. 42. What is the principle of measuring the rubber content in HIPS? Answer: In chloroform, the unsaturated double bonds in polybutadiene undergo an addition reaction with iodine chloride, and excess iodine chloride reacts with potassium iodide to generate iodine, which is titrated with Na2S and O3 , so as to determine the rubber content based on the curve. 43. If the table where the viscometer is placed is not level, is the test result high or low? Answer: The test result is on the high side. 44. When analyzing the rubber content in HIPS, why should the iodine bottle be placed in a dark place for 30 minutes? Answer: Minimize the effect of ultraviolet light on the solution, so that the reaction is sufficient and complete. 45. Measuring the solid content for too long or too short time will have a negative impact on the measured value. What is the impact? Answer: Generally, if the time for measuring solid content is too long, the result will be low, and if the time is too short, the result will be high. 46. If the solid content of SAN latex is high, what impact will it have on the melt index? Answer: If the solid content of SAN latex is high, it means that the polymer molecules are relatively large, and the carbon chains are relatively long, so the MI value during measurement is relatively low. 47. What are the poisoning effects of chloroform? Answer: Inhaling a large amount of this substance can cause poisoning and is also a carcinogen. Long-term inhalation can cause serious consequences. It can react violently with many compounds, such as: propylene + caustic alkali, sodium hydroxide + methanol, etc. It can oxidize into highly toxic phosgene. 48. What are the toxic properties of dichloroethane? Answer: It is moderately harmful to the oral cavity and epidermis, and can cause pulmonary edema. 49. What are the toxic properties of iodine chloride? Answer: It irritates the skin, eyes and cornea, and also damages the oral cavity and epidermis. It decomposes when heated and releases toxic gases that react violently with aluminum foil, cadmium sulfide, aluminum sulfide organophosphorus, etc. 50. When choosing an indicator for acid-base titration? Answer: Choose according to the discoloration range of the indicator.
51. What is water hardness? Answer: It refers to the amount of soluble calcium salts and magnesium salts contained in the water. 52. What is the temporary hardness of water? Answer: It is called the hardness of water formed by carbonates. 53. What is a stabilizer? Answer: Stabilizers, also known as sunscreen agents, are substances that can absorb or reflect ultraviolet light, preventing light from directly entering the polymer, thereby effectively inhibiting photoaging. 54. Which substances have the function of stabilizers? Answer: Substances with stabilizers are mainly some inorganic fillers and pigments such as carbon black, TiO3, ZnO, etc. 55. If the measured TB value is too high, what are the possible reasons? Answer: The volumetric flask is not clean, which makes the measured solution turbid. (2) The cuvette is not clean (3) The sample amount is too much (4) The dilution volume is not enough. 56. What is ABS latex? Answer: ABS polymerization adopts the emulsion graft polymerization method. PB latex, SM monomer, and AN monomer are polymerized into ABS latex under the action of catalysts, emulsifiers, and redox agents. 57. What is an emulsifier? Answer: There is a type of substance that can turn oil and water into a relatively stable emulsion that is difficult to separate. This process is called emulsification. A substance that can wait for oil and water to become an emulsion is called an emulsifier. 58. What is the analysis principle of DNPC (I-77) in styrene? Answer: Mix DNPC in the sample with NaOH to cause color interference on the compound, thereby determining the absorbance value and using the curve to determine the content. 59. What are the main poisoning symptoms of chloroform? Answer 1) Skin contact, dryness and cracking, (2) Inhalation of high and high concentration chlorine poisoning, dizziness, nausea* * , (3) Chronic poisoning, liver, heart and kidney damage. 60. What are the effects of potassium permanganate and potassium dichromate poisoning? Answer: These two substances can severely stimulate mucous membranes and cause inflammation and ulcers. Chromium compounds can cause cancer. 61. What are the physical properties of benzene? Answer: It is a colorless liquid with a melting point of 5.5°C and a boiling point of 80°C. It has an aromatic odor, is insoluble in water, is soluble in alcohol ethers, and is flammable. 62. What are the effects of benzene poisoning? Answer: Benzene is highly fatty and adsorbs on the surface of nerve cells, causing * * Effects, severe poisoning, long-term coma, blood pressure drop, and pupil dilation. 63. What should I pay attention to when analyzing iodometry? Answer: 1) Iodine is volatile, so the iodine bottle is tight and the mouth of the bottle is sealed. (2) The titration speed is appropriate and should not be too fast. (3) The reaction time is strict and must be completed within the specified time. (4) Avoid direct light. 64. What is constant weight? Answer: The difference between two consecutive weighings should not exceed 0.0002g. 65. What is viscosity? Answer: When a liquid undergoes countercurrent motion under the action of external force, there is frictional resistance between the liquid molecules, so the liquid has a certain viscosity, which is called viscosity. 66. What is displacement titration? Answer: When some substances cannot be titrated directly, it can react with another substance to replace a certain amount of substance that can be titrated, and then titrate with an appropriate titrant. This method is called displacement titration. 67. What is the applicable range of the measurement method for polymer content in industrial styrene? What should be done when the polymer content is high? Answer: 0--15mg/kg (ppm). When it exceeds 15mg/kg (ppm), appropriate dilution should be performed before measurement. 68. What are the control indicators for TBC of styrene products? What is TBC called? Answer: 10--30mg/kg (ppm) p-tert-butylcatechol 69. What should be paid attention to when collecting or analyzing styrene samples? Answer 1) Styrene monomer is flammable and should be kept away from heat and fire sources. (2) It cannot come into contact with peroxides, inorganic acids and aluminum trichloride to avoid exothermic polymerization. (3) High concentrations of liquid styrene and its vapor are irritating to the eyes and respiratory system. Samples should be taken from the upwind vent and analyzed in a fume hood. 70. Please explain what kind of agent D213/T213 is, what are its analytical indicators? What is the standard solution used? Answer 213/T213 is a high-concentration potassium hydroxide solution with an analytical indicator greater than 30%. It is titrated with a 1.0 mol/L hydrochloric acid standard solution. 71. If the latex is not filtered during TB analysis, what impact will it have on the analysis results? Answer: Since the latex is not filtered, the small solid particles in the latex will affect the turbidity value. According to the law A=KCL, the turbidity of the solution is large, making the latex value higher. At this time, according to TB=(ABS/W×10TS)×1000, the value is higher than 72. What are the possible reasons if the solid content of the sample does not change during the analysis of ABS chemicals? Answer 1) Sampling problem, the sample bottle is not clean, or the sample is filled with other samples (2) Uneven sampling (3) Problems with the sampler (4) There is a problem with the process chemicals (5) There is a problem with the instrument temperature 73. What should be paid attention to during the ABS sampling process? Answer 1) Before sampling, open the agitator of the tank (2) Replace the sampler with chemicals 3-5 times (3) The sample taken has a certain depth, such as about 1m below the liquid surface. (4) There must be cooperation from process operators. 74. When you find that the sample data being analyzed is abnormal, how do you deal with it? Answer 1) First check whether the operating conditions of your analytical instrument are correct (2) Whether the wrong sample was taken (3) Whether the reagents used have expired (4) Do it again (5) Contact the process to see if the wrong medicine was added (6) Keep the analyzed sample. 75. What is sampling? Answer: It refers to taking a small amount of representative samples from a certain number of batches of materials for inspection. The so-called sample number refers to the sample used for testing. 76. What should you pay attention to when sampling? Answer 1) The sample collected is representative (2) Under special circumstances, take correct measures to ensure personal safety (3) How much is a sampling bottle with a volume of 3/4? 77. What substances are copolymerized to ABS resin? Answer: ABS is a ternary copolymer of styrene, butadiene, and acrylonitrile. 78. Which substances are copolymers of ABS resin? Answer: ABS is a ternary copolymer of styrene, butadiene, and acrylonitrile. 79. What is the general drying time for measuring the solid content of chemicals? What is the solid content of latex? Answer: It usually takes one hour to measure the solid content of chemicals in an ABS device, while it usually takes 40 minutes to measure the solid content of latex. 80. In the Lambert-Beer law, what are the definitions of each symbol in A=KCL? Answer: A: Indicates the absorbance of the solution, K: Absorption constant (molar absorption constant), C: \Concentration of the solution mol/L, L: Liquid layer thickness (thickness of the cuvette) * } 81. Do you know what brands of refrigerator plates our factory produces? Answer: There are three brands: ABS772, ABS770, and ABS775. 82. What is the process of PB production? Answer B is produced by emulsion polymerization method. KSP (potassium persulfate) is used as the initiator to polymerize butadiene monomer to form a polybutadiene liquid emulsion. In a vacuum state, add D209 hot water, N-70 and 3% NaOH. When the water is added Start stirring at 3 tons. When KSP is added for 18 hours, take samples for analysis. After that, take samples and analyze TS, PH and TB every 4 hours. After the analysis is qualified, add the stabilizer (STB, D205) and then send it to the stripping tank D207. 83. How to judge whether the D205 (STB) sample is qualified? How to deal with it? Answer 1) Visual inspection: Visually check whether the solution is transparent. If it is opaque, contact the process in time (extend the stirring time) (2) Check TS and PH. For TS↑, add PW (hot water), for TS↓, add OA (stabilizer), for PH↑, add PW or OA (stabilizer), and for PH↓, add KOH. 84. What are the main types of PB latex? Answer B There are three main brands of latex, namely HN-800, HN-820, and HN-900. Currently, HN-800 is mainly produced. 85. What kind of latex can be produced by grafting reaction? Answer: AS. 87. Which grades of AS latex are mainly produced by the ABS equipment of our factory? Answer: There are two general types, H-1158 and H-1163, and three heat-resistant types, S-1200/1250/1300. 88. What should I pay attention to when sampling grafting chemicals? Answer 1) Since the grafting reaction reagents SN-100 and N-70OA are heated to above 80℃ indoors, they should not come into contact with the skin. (2) SN-100 will change color if the preheating temperature is too high. Pay attention to the color of the liquid. 89. What is the process of D255? Answer 255 is an emulsifier preparation tank. It mainly adds OA (oleic acid) and stirs for 40 minutes, then checks the PH. TS, after passing the analysis, add TBHP (tert-butyl hydroperoxide) and stir for 10 minutes before checking TS and PH. 90. What items are analyzed for styrene before leaving the factory? Answer: Analysis of SM, purity, TBC, color, polymer, aldehyde content, peroxide. 91. What are the calculation formulas for solid content and latex turbidity? Explain the meaning of each symbol. Answer: Solid content W2-W0 W0: Aluminum foil weight g TS%= ──── * 100 W1: Sample weight before drying + aluminum foil weight W1-W0 W2: Sample weight after drying + aluminum foil weight TB=──── * 1000 ABS: light absorption value TS * 10 * W TS: Solid content of the latex (%)%}.X3] ;Z:E \ ku W: Sample weight (g) 92. Detailed description of the control indicators of D203 and D245? Answer 203 and D245 are both potassium persulfate PH: 3.4～7.0 TS: 3.5～3.8 93. What is the formula for calculating the volatile content of PP powder? Answer: AB Z Volatile content (ppm)= ──── * 106 AC A: Sample before heating + weight of aluminum boat (g) B: Sample after heating + weight of aluminum boat (g) C: Weight of aluminum boat (g) 94. How many selection methods are there for humidity balance MB-200? Answer: There are four types 95. In what way is the humidity balance MB200 tested? Answer: The balance is tested in Normol Mode. (Normal mode)| 5. Instrument. Equipment maintenance 96. What should be done when the electrode of the pH measurement sample is unstable? Answer: When the pH electrode shows instability during measurement, the electrode bulb is contaminated and the response slows down. This is based on the nature of the contaminants. Use an appropriate solution for cleaning, such as: organic oils, dilute hydrochloric acid (or alkaline) Resin polymer alcohol, propylene and ether 97. What is the electrode of the pH meter in your workshop? Can it be immersed in distilled water or acidic fluoride solution for a long time? Answer: The electrode used is E-201 composite electrode. The composite electrode cannot be immersed in distilled water or acidic fluoride for a long time, and prevent contact with silicone grease. 98. When measuring TBC, if the cuvette is dirty, what impact will it have on the results? How should it be handled? Answer: (1) The result is too large, (2) Soak the sample cell with potassium dichromate washing solution for 1-2 hours. 99. When Lamd11 is scanning, why can't you open the cover to take the sample? Answer: When the instrument is scanning, if you open the cover to take the sample, strong light will directly shine on the photoelectric tube, which will fatigue the photoelectric tube, affect the sensitivity of the instrument, and reduce the service life. 100. What should you pay attention to when using the conductivity meter? Answer: Understand the conductivity range and the control indicators of the measured solution, calibrate before use, and adjust the compensator R and w2 of the electrode to the position corresponding to the electrode constant.
101. Why is desiccant placed in the spectrophotometer? Answer: Because the main electrode of the optical path system of the instrument will be affected by moisture, which will affect the light effect, so a desiccant is placed in the instrument. 102. How to judge whether the instrument is easy to use if the signal of the pH meter is unstable? Answer: First select the PH electrode. If the signal of the new electrode is still unstable, it is judged that there is a problem with the instrument. (2) You can replace the electrode with another instrument to see if there is still a problem with the signal. If there is, then it is determined that there is an electrode problem. 103. What factors affect the accuracy of the humidity balance? Answer 1) Calibration of the balance (2) Whether the weighing sample volume meets the requirements (3) Whether the sample itself is uniform. 104. The water sample collected for measurement should be (uniform) (representative) and not change its (physical and chemical characteristics) 105. The turbidity index of the circulating water in our factory is (≤20mg/L) 106. The constant temperature incubator should be placed away from light to prevent the growth of algae in the culture bottle and ensure the accuracy of the analysis results. 107. Most wastewater samples for measuring biochemical oxygen demand need to be cultured (after dilution) for further measurement. The purpose is to reduce the (organic matter concentration) in the wastewater and ensure sufficient dissolved oxygen. 108. What are the sources of errors in iodometry? Answer: (1) Iodine is volatile and easy to lose, (2) iodide ions are easily oxidized by oxygen in the air in acidic solutions and iodine is precipitated. 109. Conductivity index of secondary desalted water? Answer: ≤0.5μs/cm 110. What factors affect the COD measurement results? Answer: The type and concentration of the oxidant added, the acidity of the reaction solution, the reaction temperature and time, the presence of the catalyst, etc. 111. Why should the conditions be strictly controlled when measuring COD? Because COD is a conditional indicator, the conditions must be strictly controlled and the operating steps must be strictly followed. What is the impact of temperature on the conductivity measurement? Answer: As the temperature increases, the conductivity increases. 112. What is the turbidity index of the circulating cooling water in our factory? Answer: ≤20mg/L 113. The measurement index of calcium hardness?| _Answer: 100-500mg/L 114. What are the commonly used water sample containers? Answer: Hard glass ground-mouth bottles and polyethylene bottles 115. The longest storage time of water samples? Answer: Clean water samples are stored for 72 hours, slightly contaminated water is stored for 48 hours, and contaminated water is stored for 12 hours. 116. When measuring COD, what should be done if the water sample has high chloride ion content? Answer: When the chloride ion content in the water sample to be tested exceeds 30mg/L, 0.4 grams of mercury sulfate should be added to the reflux Erlenmeyer flask first, then the water sample should be added and shaken well. 117. How should the water sample to be measured for COD be processed and stored? Answer: (1) If the wastewater sample is very unstable, it should be analyzed quickly (2) If the wastewater sample contains suspended matter that is easy to settle, it should be thoroughly mixed (3) If it cannot be analyzed in time, use sulfuric acid to adjust the pH
151. Industrial circulating cooling water can be measured for turbidity (spectrophotometry). 152. W-331 agent added during circulation is an organophosphorus corrosion inhibitor, which plays the role of (corrosion and scale inhibition). 153. (Iodometric method) is the basic method for measuring dissolved oxygen in water. 154. Circulating water mainly includes (carbonate) (bicarbonate) (hydroxide) and alkalinity. 155. There is an (inversely proportional) relationship between dissolved oxygen in water and oxygen consumption. 156. When extracting oil from water, use (carbon tetrachloride) as the extraction agent. 157. When measuring calcium ions, use (EDTA) standard solution to titrate until (fluorescent yellow-green) disappears, and the appearance of red is the end point. 158. Through microscope observation, the (type and quantity) of bacteria in activated sludge can be known, so as to judge the treatment effect. 159. What is biochemical oxygen demand? Answer: It refers to the amount of dissolved oxygen required for the biochemical process of microorganisms decomposing organic matter in wastewater under aerobic conditions. 160. What nutrients are added to the five-day biochemical oxygen demand dilution water? Answer: Calcium chloride, ferric chloride, magnesium sulfate, phosphate buffer. 161. What is activated sludge? Answer: It is mainly caused by the aggregation of a large number of microorganisms growing in sewage. In activated sludge, in addition to microorganisms, there are also some inorganic substances and decomposing organic substances. 162. What indicator is used to measure alkalinity? ` Answer: Phenolphthalein indicator, methyl orange indicator. 163. What is the function of measuring the conductivity of pure water? Answer: At a certain temperature and a constant flow rate of 0.05m/s, testing the conductivity of water samples can determine the purity of pure water. 164. What does chemical oxygen demand (COD) refer to? Answer: Under certain conditions, the amount of oxidant consumed when treating water samples with strong oxidants. 165. What does COD reflect? Answer: It reflects the degree of water pollution by reducing substances. 166. What method is required to measure COD? Answer: For industrial wastewater, my country stipulates the potassium dichromate method. 167. What are the requirements for COD measurement data processing? Answer: The results should retain three significant figures.| 168.What is the total volume of COD used for titration solution? Why? Answer: The total volume must not be less than 140mL, otherwise the titration end point will not be obvious due to too high acidity. 169.W-331 is proportional to which ion in the water sample? Answer: It is proportional to the phosphate content in the water, the conversion factor is 14.1 170. On what basis is the indicator for acid-base titration selected? Answer: The principle is that all or part of the change range of the acid-base indicator is within the sudden jump range of the titration. 171. What is the commonly used desiccant at the bottom of the dryer? Which one can be dried and reused? Answer: Color-changing silica gel and anhydrous calcium chloride. Color-changing silica gel can be reused. 172. What is the role of alum-molybdate in the analysis of W-331 determination? Answer: Aluminomolybdate reacts with orthophosphate to form phosphorus vanadium molybdenum heteropoly acid chromium compound, which can be quantitatively determined by equal exchange colorimetry. 173. Why is turbidity analysis necessary? Answer: High turbidity can cause equipment corrosion and scaling, so it must be monitored. 174. What method is used for turbidity analysis and what are the instrument conditions? Answer: Spectrophotometry, wavelength 420nm, 3cm cuvette 175. What is the application range of turbidity measurement by spectrophotometry? Answer: It is suitable for the determination of turbidity in industrial water circulation cooling water, its range is 0-45mg/L 176. What is conductivity? Answer: It refers to the conductivity of the solution when the electrode area is 1cm~2 and the inter-electrode distance is 1cm _ 177. How is calcium hardness measured? Answer: Calcein can form a fluorescent yellow-green complex with calcium ions in water. When pH>12, use EDTA standard solution to titrate calcium. When it is close to the end point, EDTA takes away the calcium bound to the indicator, and the yellow-green fluorescence of the solution disappears and turns into the red color of the mixed indicator, which is the end point. 178. What is the principle of pH positioning calibration? Answer: The pH value of the known solution must be reliable, and the closer the pH value is, the better the measured value is. 179. What are the standard buffer solutions for measuring pH in my workshop? Answer: Three types, PH=4, PH=7, PH=10 180. What is the purpose of adding ethanol in the measurement of W-331? Answer: Why is it heated and boiled in the measurement of stable color solution 180.W-331? Answer: How long does it take to heat and boil all the organic phosphates into orthophosphate 182. W-331? 5v: V0J8x2a Answer: The boiling time is 30 minutes 183. W-331 measurement principle? Answer: Use the strong oxidant potassium persulfate to heat and boil in a strong acidic solution to convert the organic phosphate into orthophosphate, and then react with ammonium molybdate-metafluorate to form a phosphorus vanadium molybdenum heteropoly acid complex, which is then measured with a spectrophotometer. 184. What is turbidity? Answer: When there are various dissolved substances or insoluble clays, suspended solids, etc. in the water, the water becomes turbid. The degree of turbidity expressed as a numerical value is called turbidity 185. What is dissolved oxygen? Answer: The oxygen dissolved in the water after the water body exchanges with the atmosphere or undergoes chemical or biochemical reactions is called dissolved oxygen 186. What is the content of dissolved oxygen related to? Answer: It is related to the partial pressure of oxygen in the air, atmospheric pressure, water depth, water body state, etc. 187. How does dissolved oxygen change when algae reproduce in the water body?| Answer: When algae reproduce, dissolved oxygen can be supersaturated. 188. What impact does organic matter and reducing substances in the water body have on dissolved oxygen? Answer: Water bodies polluted by organic matter and reducing substances can reduce dissolved oxygen. 189. Briefly describe the measurement principle of chemical oxygen demand (ie COD) Answer: In a strong acidic solution, a certain amount of potassium dichromate oxidizes the reducing substances in the water sample. The excess potassium dichromate is used as an indicator, and ferrous ammonium sulfate solution is used to drip back. Calculate the amount of oxygen consumed by the reducing substances in the water sample based on the amount. 190. To measure the COD value by the potassium dichromate method, add the standard solution indicator to the sample, and what are the titration standard solutions? Answer 1) The standard solution added to the sample is potassium dichromate (2) The indicator is ferrous ferrous (3) The standard solution used to titrate the sample is ferrous ammonium sulfate. 200. What analytical method is used to measure the oil content in water? What is the solvent used? Answer: The oil content in water is measured by instrumental analysis, and the solvent used is carbon tetrachloride.
201. What water samples are suitable for measuring dissolved oxygen by iodometric method? Answer: In the absence of interference, iodometric method is suitable for various water samples with a dissolved oxygen concentration of 0.2-2.0 mg/L. 202. Why should we monitor the residual chlorine content in circulating water? Answer: Passing chlorine in circulating water can achieve the purpose of sterilization and algae removal, but excessive amounts will also increase the tendency of equipment corrosion, so the residual chlorine in circulating water must be controlled within an appropriate range. 203. What is dry filtration? Answer: Use dry filter paper and a dry funnel to filter the solution, and collect the filtrate in a dry container. The initial filtrate should be discarded during dry filtration. 204. What is the principle of dew point measurement? Answer: Based on the relationship between the temperature of water vapor condensation in the gas and the water vapor content is proportional, that is, the more water vapor, the higher the condensation temperature (i.e. dew point). 205. What are the precautions for measuring dew point? Answer: Avoid rapid cooling, the gas flow rate must be controlled appropriately, and observation and judgment must be accurate. 206. What is the moisture dew point? Answer: Under constant pressure, the temperature when the water vapor in the gas reaches saturation. 207. What is the significance of measuring biochemical oxygen demand (BOD5)? Answer: Biochemical oxygen demand (BOD5) is one of the main indicators to measure the quality of wastewater. It represents the amount of dissolved oxygen required for the biochemical process of microorganisms decomposing organic matter in wastewater. The higher the value, the worse the water quality. 208. Why is hydrochloric acid added when measuring the oil content in water? Answer: Hydrochloric acid is used as a demulsifier, which can extract emulsified oil for measurement. 209. What is the purpose of measuring dew point?_V Answer: Measuring the dew point of the gas is to understand the water content in the gas. Measuring the dew point of the gas can be converted into the water content of the gas. 210. What are the requirements for the extraction agent carbon tetrachloride in the determination of oil content in water? Answer: The analysis sample and the extraction agent used for zeroing should be of the same batch number, or the extraction agents of different batch numbers should be stored in a large container and mixed evenly before being used in separate packages. 211. Why should a blank be used when measuring chlorine? Answer 1) Eliminate the influence of distilled water and end point judgment on the determination (2) Eliminate the analysis error caused by the silver nitrate consumed as the indicator potassium chromate. 212. What does suspended matter refer to? Answer: Suspended matter refers to the solid matter left on the filter and dried to constant weight at about 105°C. 213. The discoloration range and color change of methyl orange and phenolphthalein? Answer: The discoloration range of methyl orange is PH value 3.1-4.4, from red to yellow, and the discoloration range of phenolphthalein is 8.2-10.0, from colorless to red. 214. When measuring the silica content in desalted water, what are the requirements for the temperature of the water sample? Answer: Since temperature affects the reaction, the temperature of the water sample is required to not be lower than 20°C, and the temperature difference between the water sample and the standard solution should not exceed ±5°C. 215. What is the principle of measuring the silica content in desalted water? Answer: At an acidity of PH 1.2-1.3, silicon dioxide (active silicon) reacts with ammonium molybdate to form silicon molybdenum yellow, which is then reduced with stannous chloride to form silicon molybdenum blue. The chroma of this blue is related to the content of silicon dioxide (active silicon) in the water sample. 216. Will there be any interference from suspended solids or coloring in the water sample for measuring dissolved oxygen? How to eliminate it? Answer: There will be interference. Potassium aluminum sulfate can eliminate the interference caused by suspended matter or colored organic matter, and the alum flocculation method can also remove the interference caused by suspended matter. 217. What are the wavelength ranges of ultraviolet light, visible light, and infrared light? Answer: Ultraviolet light wavelength: below 400nm, visible light wavelength: 400-760nm, infrared light: greater than 760nm. 218. Why is potassium and sodium tartrate solution added when measuring ammonia nitrogen in water using Nessler's reagent colorimetry? Answer: Adding potassium and sodium tartrate solution can eliminate the interference of metal ions such as calcium and magnesium. 219. What is the principle of measuring total iron ions in circulating water?) Answer: Total iron, that is, divalent and trivalent iron ions, and trivalent iron ions are reduced to divalent iron ions with hydroxylamine hydrochloride. Divalent iron ions react with o-phenanthroline to form orange-red complex ions under the conditions of PH 3-9, which are then colorimetrically measured. 220. What instrument is used to measure conductivity at the desalted water station? What properties of the solution does the conductivity represent? Answer: The DDS-11A conductivity meter is used to measure the conductivity at the desalted water station. The conductivity of the solution represents the conductivity of the solution. 221. What factors are related to the conductivity value of pure water? Answer: The conductivity value of pure water is related to the type and content of ions in the water, the temperature of the water sample and the flow rate of the water sample in the conductivity cell. 222. How many forms of residual chlorine exist in the water? Answer: There are three forms of residual chlorine in the water: total residual chlorine, free residual chlorine and combined residual chlorine. 223. What are the circulating water analysis projects in our factory? Answer H, turbidity, W-331, calcium hardness, total iron, alkalinity, chloride ions, silicon dioxide. 224. What does sludge concentration mean? Answer: It refers to the weight of dry sludge contained in one liter of suspended mixture. 225. Why should sludge concentration be measured? Answer: Because the concentration of activated sludge indicates the number of microorganisms contained or the ability to oxidize organic matter, ensuring a certain concentration of activated sludge is one of the keys to increasing the treatment load. 226. What does sludge concentration reflect? Answer: It reflects sludge settling performance and sludge quality. 227. What should you pay attention to when drying glass instruments? Answer 1) The oven temperature is 105--120°C, and the drying time is about 1 hour. (2) The weighing bottles should be placed in a desiccator for cooling and storage after drying. (3) The measuring instruments cannot be placed in the oven for drying. 228. How to store the cuvette after use? Answer: Wash it after use, place filter paper in a small porcelain dish, invert it to dry and store it in a cuvette box or a clean vessel. 229. What is the function of a circulating water cooling tower? Answer: In the cooling tower, circulating water and air exchange heat, thereby reducing the temperature of the circulating water and meeting the process requirements. 230. What are the methods of weighing samples? Answer: Fixed weighing method, reduction method, ampoule method. 231. Which type of sample is suitable for weighing the reduction method? Answer: It is suitable for weighing substances that absorb water, is easily oxidized or reacts with carbon dioxide, and is suitable for weighing several copies of the same sample. 232. Which type of sample is suitable for the ampoule method? Answer: It is suitable for weighing volatile liquid samples. 233. What should you pay attention to when opening the dryer? Answer: When opening the dryer, do not lift the lid upwards. You should hold the dryer with your left hand and carefully push the lid open slightly with your right hand. Wait until the cold air slowly enters before you can fully push the lid open. The lid must be placed on the table. 234. Common sense for using discolored silica gel? A: Discolored silica gel is blue when dry and turns pink when it gets wet. You can bake the damp silica gel at 120°C until it turns blue and use it repeatedly until it breaks and cannot be used. 235. Why is it said that the dryer is not absolutely dry? Answer: Because the ability of the desiccant contained in the dryer to absorb moisture has a certain limit, the air in the dryer is not absolutely dry, but the humidity is low. 236. Why should corrosion and scale inhibitors be added to the circulating water? Answer: Because circulating water can corrode and scale equipment, corrosion and scale inhibitors must be added to the circulating water. 237. Methods to prevent circulating water from corroding and scaling equipment? Answer: (1) Cleaning (2) System pre-film treatment before start-up (3) Adding corrosion and scale inhibitors during operation (4) Strengthening monitoring and analysis 238. What is the role of the anode bed in the desalted water system? Answer: The anode bed can remove cationic impurities in the water. 239. How to store the burette? Answer: Rinse the solution inside, rinse it with pure water and then fill it with pure water. Cover the short glass test tube, or it can be inverted and clamped on the burette clamp. 240. What is the role of the mixed bed in the desalted water system? 'Answer: To further remove anionic and cationic impurities that are difficult to remove. 241. What are the hazards of chromium compounds to humans? Answer: It can cause severe irritation to mucous membranes, causing inflammation and ulcers. Chromium compounds can cause cancer and be poisonous if swallowed. 242. The main pollution components in chemical sewage? Answer: Aromatic organic pollutants and acrylonitrile, etc. 243. Principle of alkalinity determination? Analytical Chemistry Forum_ Answer: The pH value range for the color change of phenolphthalein indicator is 8.0-10.0, and the pH value range for the color change of methyl orange indicator is 3.1-4.4. When the standard acid is added, phenolphthalein and methyl orange change color at their color change points respectively. This method uses phenolphthalein and methyl orange indicators respectively instead of the acidimeter to indicate the end point. 244. What should you pay attention to when measuring dissolved oxygen? Answer: (1) During the operation, do not allow bubbles to enter the water sample bottle, (2) The water sample should be fixed as soon as possible (3) The titration time should not be too long. 245. What is the role of the sewage grease trap? Answer: Remove floating oil and part of the suspended matter in the sewage. 246. Determination principle of chloride ions? Answer: In neutral media, silver nitrate reacts with chloride to form a white precipitate. When all the chloride ions in the water sample react with silver nitrate, Excessive silver nitrate reacts with the indicator to form a brick-colored precipitate. 247. Why should benzene series be measured in wastewater? Answer: Because if the sewage contains too much benzene series, it will cause adverse reactions in humans and organisms. 248. Why should acrylonitrile be measured in wastewater? Answer: Because acrylonitrile is a poison, the discharge concentration should be strictly controlled. 249. What are the most basic requirements for weighing a sample? Answer: Fast and accurate. 250. The function of the flotation cell? Answer: Remove the emulsified oil and part of the suspended solids in the sewage. Part of the COD. 251. The principle of measuring ammonium nitrogen by Nasler's reagent colorimetric method? Answer: Ammonium nitrogen reacts with Sodium reagent to form a yellow-brown complex. The color of the complex is proportional to the content of ammonium nitrogen, which is measured by spectrophotometry. 252. How to eliminate the interference of calcium, magnesium and other ions when measuring ammonium nitrogen by Nessler's reagent method? Answer: Add potassium sodium tartrate solution for complex masking.
Which company's exam question is this? Very basic knowledge!
This is the compound I asked for from the laboratory of the coal-to-olefins plant.* Questions are posted on the web page for everyone’s reference and study. *