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How to keep glass instruments dry?

The glass instruments used for chemical analysis should be washed and dried after each experiment. The instruments used in different experiments have different requirements for drying. Generally, the beakers, conical flasks and other instruments in quantitative analysis can be used after washing, but many instruments used in organic chemistry experiments or organic analysis require drying, and some No water marks are required, and some require no water. The instrument should be dried according to different requirements.

Cleanliness standards of glass instruments

In chemical experiments, in order to prevent impurities from entering the reaction system and affecting the reaction conditions and observation of experimental phenomena, clean glass equipment must be used. The cleaning of the instrument should be carried out immediately after each experiment. This is because on the one hand, it is clear about the nature of the dirt at that time so that it can be removed in an appropriate way; on the other hand, it is also ready for the next experiment.

General cleaning method of glass instruments

Choose a suitable brush, moisten the brush and the instrument with water, and wash the inner and outer walls of the instrument with the brush with decontamination powder (decontamination powder should not be used for the grinding bottle, so as not to damage the grinding mouth), and remove the dirt on the glass instrument After that, rinse it off with tap water.

If a high degree of cleanliness is required, a small amount of distilled water needs to be rinsed two to three times. There should be no water drops on the bottle wall of a cleaned glass instrument. If there are water drops, it needs to be washed again. It should be pointed out that the instrument after washing cannot be wiped dry with a cloth, filter paper, etc.

Some reaction residues are not easy to clean with decontamination powder. According to the specific conditions of the dirt, they can be soaked in cheaper or recycled organic solvents or cleaned with dilute acid or lye, but they cannot be used blindly to avoid waste and accidents ( For example, if the instrument with residual waves is cleaned with acetone, it will produce a powerful tear agent-brominated acetone). The old marks on the wall of the instrument can be cleaned and removed after soaking in a lotion.

Washing contraindications

1. Wash the instrument in the usual way. When washing the instrument, you should wash your hands with soap first to prevent the oil on your hands from attaching to the instrument, which will increase the difficulty of washing. If the instrument is stored for a long time with dust and dust, rinse it off with clean water first, and then use a cleaning agent to scrub or wash it as required. When rinsing with distilled water, use the method of flushing along the wall and fully shake it. The instrument after rinsing with distilled water should be neutral when checked with an indicator.

2. Use 1:1～1:9HNO3 solution to soak the glass instrument for trace metal analysis, and then wash it in the usual way.

3. When performing fluorescence analysis, glass instruments should avoid washing with washing powder (because the washing powder contains fluorescent whitening agent, it will bring errors to the analysis results).

4. When analyzing carcinogens, appropriate decontamination and night soaking should be selected, and then washed according to the usual method.

Common drying methods

In addition to cleaning, the instruments used in chemical experiments often need to be dried. The presence of water sometimes affects the speed or yield of the chemical reaction, and sometimes even makes the chemical reaction impossible. For experiments with general water-free requirements, the instrument can be used only by inverting it to dry; while for experiments with absolutely no water, the instrument needs to be dried in an oven or a hot air dryer. If you need it urgently, you can wash the cleaned instrument with a small amount of ethanol or acetone, and then dry it with a hair dryer. It must be particularly pointed out that no matter what method is used to dry the instrument, it must be cooled to room temperature before it can be taken out. Otherwise, when the hot instrument is quenched, water vapor will condense on the wall.

As long as it is not a volumetric instrument (graduating cylinder, burette, pipette, etc.), it can be dried.

1. Air dry

It is not urgent to use, and requires general drying. After rinsing in pure water, place it upside down in a dust-free place to dry the water, and then dry naturally. The instrument can be placed on a shelf with oblique wooden nails and a glass cabinet with ventilation holes.

2. Drying

The cleaned instrument is controlled to remove moisture and dried in an electric oven at a temperature of 105～120℃ for about 1 hour. It can also be dried in an infrared lamp drying box. This method is applicable to general instruments. After drying, the weighing bottles used for weighing should be cooled and stored in a desiccator. When drying instruments with solid glass plugs and thick walls, pay attention to the temperature rise slowly and the temperature should not be too high to avoid cracking, and the measuring device should not be dried in the oven.

The hard test tube can be dried with an alcohol lamp. The test tube should be dried from the bottom with the test tube mouth down to avoid backflow of water droplets and bursting the test tube. When there is no water droplets, move the test tube mouth up to remove the water vapor.

3. Dry by hot (cold) air

Elemental analyzers can be blow-dried for instruments that are eager to dry or larger instruments that are not suitable for ovens. Usually a small amount of ethanol, acetone (or finally ether) is poured into the instrument that has been controlled to remove moisture. Clean the solvent (the solvent needs to be recovered), then blow it with a hair dryer, and start blowing with cold air for 1 to 2 minutes. When most of the solvent has evaporated, blow in hot air until it is completely dry, and then blow the remaining steam with cold air to prevent it from condensing in the container. Inside. This law requires good ventilation to prevent poisoning, and no exposure to open flames to prevent explosion of organic solvents.

What should I pay attention to when drying in the oven?

To be precise, all glass instruments cannot be dried in an oven. The glassware that can be put in is used for holding rather than measuring. For example, beakers, flasks, and round-bottomed flasks are suitable for drying, and measuring tools (with graduations) such as burettes, pipettes, and graduated cylinders for glass products are not suitable for drying.

It is easy to dry the glass and the temperature should not be too high. It should be below 100 degrees. When taking it out, pay attention to wearing high temperature gloves to prevent burns. In addition, it is best to take out the instrument after the oven temperature reaches 45 degrees (or normal temperature). , To prevent the glass from breaking due to sudden cooling and heat.

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