Common mistakes in experiments, let’s learn together* and discuss experiences!

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This post was last edited by qazxsw119 on 2009-12-25 08:06. Let’s learn together about common mistakes in experiments.* and discuss experiences! Be careful when performing experiments! ! Pay attention to the timely analysis and processing of data in experiments: After each experiment, the experimental data must be analyzed in a timely manner in order to summarize the experience and understanding of the previous experiment and provide a theoretical basis for further improvement of the next experimental method. Do not wait for all experiments to be completed before analyzing. Only then will you discover one or another shortcoming, resulting in a waste of manpower, financial resources, and time. This is the most unpleasant thing. It is not advisable to conduct experiments blindly. 1. When doing experiments, you must follow the procedures. When decompressing, you must use a round-bottom flask, not a conical flask, which is prone to internal absorption and explosion. If you only recover the solvent, there is no serious problem. If you spin off the solvent to obtain a sample, extract the entire water bath, the workload... 2. Sometimes the literature may not be complete. When reacting according to the literature, think more if possible. The literature may be relatively simple, so you might as well study and discuss it more before doing the experiment. 3. Remember not to try too hard. If it is dangerous but you think it is not difficult, if you try too hard for a while, you may end up harming yourself. When doing experiments, you must be careful not to show off or brag, especially when recording data, otherwise you will not know what to remember and the experiment will be in vain. Don't get carried away when the experiment is successful, because it is easy to make stupid mistakes. When preparing reagents, the pH value and water quality are often the reasons why the experiment always fails. 4. When using a flask to heat and reflux the medicinal materials that easily float, the amount should be less than the amount that can be added normally. Otherwise, when the liquid boils, the medicinal materials will easily rush to the condenser tube, thereby blocking the lower part of the condenser tube, with direct consequences.: Bang 5. Always pay attention to observation during experiments. Can't stay away for too long. 6. When putting rubber stoppers on glass tubes and condenser tubes, be careful not to use force, which may cause long bleeding from your hands. 7. Keep markers with you. Number flasks, beakers, etc. one by one. Don't be afraid of trouble. It's better to see them clearly at a glance than to rack your brains. 8. It is best to use a small notebook. Write down step by step. When you have inspiration, write it down immediately. Go to the notebook after get off work to write. Don’t dwell on tomorrow. 9. Sign. Sometimes the marker cannot be used to write, or it needs to be kept private. It is best to label it and record it in a notebook. As time goes by, there will always be those who will never live. 10. Maintenance of important laboratory instruments. Don't expect everything to be fine if nothing happens. The instrument will be normal every day. Once something goes wrong, it will be unthinkable. 1 1. When the instrument is due for maintenance, be sure to call a professional to check it carefully. If any abnormal phenomena, sounds, or smells occur, you must carefully observe them, consult professionals promptly, and never be "self-righteous." 12. Please pay attention to the changes in voltage and water pressure at noon or at night. Some people have done the nitration reaction of trimethylbenzene for a period of time, using concentrated sulfuric acid and fuming nitric acid. Although they strictly followed the operating procedures, and after adding the nitrating reagent and letting it continue to heat and stir to stabilize, they left the laboratory to have lunch. However, when they went back after the meal, they found that the fume hood was in a mess.: All the nitrates and acids inside were flushed out, and the reflux condenser tube was folded on the experimental bench. Fortunately, no one was injured. The main culprit is unstable voltage: Many instruments were shut down during the noon period, which increased the local voltage, causing the heating device to have a delay after reaching the set temperature. This resulted in this result. Therefore, please pay attention to whether voltage changes at noon and night will affect your experiments. 13. First of all, the lab coat must fit well, and preferably the cuffs are tightened! Otherwise, the two large sleeve hems can easily cause trouble! Don’t be careless! 14. When using a rotary evaporator to evaporate the solvent, be sure to wait until the pressure is stable and the solvent evaporates before leaving. Especially when evaporating low-boiling point solvents such as methylene chloride, care must be taken to protect them. Otherwise, the final product will fall into the water, which would be like crying without tears. 15. The problem is N2, which is used as a protective gas. Those who control valves must pay attention to the control valve! 16. Commercially available polyamides have certain particle size specifications, and the commonly used ones are 60-90 mesh and 80-100 mesh. They must be screened and classified before filling. Once, I used domestic polyamide (80-100 mesh) to load it without sieving in advance, and put one column each in the wet method and the dry method. As a result, the eluent could not be washed out because the particles were too fine and blocked the entire column. So I sieved it and found that only 1/6 of it was 80-100 mesh, and most of it was ultra-fine powder, exceeding 120 mesh. So the screened out 80-100 mesh was reloaded, and the eluent could be washed smoothly. In addition, only a thin layer of absorbent cotton should be added before loading the column. It should not be too thick or pressed too tightly, otherwise the eluent will not be able to wash out. In addition, after filling the column, the top must be pressed down with a filter, not cotton. 17. Experiments require different gloves for different reagents. Do not try to be convenient. 2. Be sure to check the equipment used before the experiment. 18. 3 lessons from vacuum distillation: The receiving bottle must not be a conical flask by chance. Dismantle the device immediately after finishing. Don't leave the Erlenmeyer flask empty. 19. The importance of wiping the table: I didn't wipe off the oil on the table, and ended up setting it on fire, along with my own sleeves!