Common laboratory operations taboo 2

Experimental safety is an eternal theme in the experiment. The rules of the experiment are not dogma, but some schemes that are really designed for your experimental safety. Therefore, only if you observe it well, you will not have any regrets. Now we will sort out some tips. For your reference.

1. Fatigue work is strictly prohibited.

2. The heating test tube must not be heated centrally, and the mouth of the test tube must not be aimed at people, so as to prevent the liquid from overheating and flushing.

3. It is strictly forbidden to directly heat all organic solvents in the flask. This is the most dangerous. If the solvent is exposed or the bottom of the bottle breaks, the operator next to it is very dangerous.

4. When using high-risk solvents such as chloroform, carbon tetrachloride, methanol and benzene, or strong irritating gases such as hydrochloric acid, pay attention to exhaust ventilation.

5. Alkaline substances are forbidden in acid burettes, otherwise it will corrode the frosted glass part and the tube wall, resulting in water leakage and inaccurate volume; strong oxidizing reagents such as potassium permanganate and potassium dichromate are strictly prohibited for basic burettes. It is a neutral substance, try to use a basic burette (basic burette is easy to operate).

6. Oxidizing acids such as sulfuric acid, nitric acid, etc., pay attention: it is safe to use. If you accidentally drop it on the body, use water to wash, and then wash with sodium bicarbonate solution. Don't ignore it because the concentration is very low, because, with the moisture Evaporation, the concentration of sulfuric acid increases, and the original washing sulfuric acid also becomes concentrated sulfuric acid.

7. Vacuum distillation is a very dangerous operation. Remember, during vacuum distillation, people must not approach the reaction device and must wear protective equipment such as goggles. Because the vacuum distillation depends on the quality of the equipment, the small flaws of the glass container will be compressed by the external atmospheric pressure during the decompression. If there is a crack, the entire glassware will burst and the experimenter will be injured.

8. Don't forget to add zeolite during any solvent reflux operation (of course, if it has a solid powder raw material, it can be used as zeolite), if you forget to add zeolite during the reaction, it is forbidden to add it when the liquid is very hot! Otherwise, adding zeolite at this time will stimulate the overheating energy of the liquid itself, causing the liquid to flush up to a few meters, and the overheated solvent will be sprayed everywhere. If it is a toxic solvent, it is even more unimaginable.

9. All organic waste liquid must be put into the waste liquid tank, and it is forbidden to pour into the sewer, causing environmental pollution. All high-concentration inorganic waste liquids, including acid and alkali and all toxic waste liquids, such as arsenic reagents, are strictly prohibited from being poured into sewer.

10. For all operations in the experiment, you must first learn the teacher's standards, and then perform your own operations. It is often seen that students don't even know how to take the burette, how to do the burette (especially the basic burette).

11. When experimenting with ether, pay attention to exhaust air and fire prevention.

All the operations of the experiment are actually a cumulative process. Don't think that the experiment is unimportant. On the contrary, the experiment is sometimes more important than the theory. Although the middle school experiment may not help you get into university, the experiment cannot be ignored in the knowledge system of chemistry. A very simple operation such as the end point titration of acid-base titration, the mastery of 1/2 drop and 1/4 drop, can often see the basic quality of a person's chemistry. If you are committed to the chemistry business, basic chemical operations are also items that need to be assessed, including the preparation of standard concentration solutions, which we have learned in middle school.