Is your glassware drying method correct?

The glass equipment used for chemical analysis shall be cleaned and dried after each test. Instruments used in different experiments have different requirements for drying. In general, beakers such as beakers and conical flasks can be used for cleaning in quantitative analysis. Many instruments used for organic chemistry experiments or organic analysis need to be dried. Some instruments do not need water marks, and some instruments do not need water. The instrument shall be dried according to different requirements.

Cleanliness standard for glass instruments

In chemical experiments, in order to avoid impurities entering the reaction system, affecting reaction conditions and observing experimental phenomena, clean glass instruments must be used. Clean the instrument immediately after each test. This is because, on the one hand, the nature of the dirt was very clear at that time, so it could be removed in an appropriate way; On the other hand, it is ready for the next experiment.

The general cleaning method for glass instruments is:

After selecting a suitable brush, wet the brush and instrument with water, brush the inner and outer walls of the instrument with a brush, and dirt the powder after removing the dirt on the glass instrument (decontamination powder should not be used for the grinding bottle to avoid damage to the grinding). Afterwards, rinse with tap water. If the cleanliness is high, it needs to be flushed with a small amount of distilled water for two or three times.

There should be no water drops on the clean Glass Bottle wall. If there are water drops, they need to be cleaned again. It should be noted that the cleaned instrument cannot be wiped dry with a rag, filter paper, etc. Some reaction residues are not easy to clean with detergent. Depending on the specific conditions of the pollutants, they can be immersed in low-cost or recycled organic solvents. They can be cleaned with dilute acid or alkali solution, but should not be used blindly to avoid waste and accidents. (For example, if the residual wave instrument is cleaned with acetone, a strong tearing agent - bromoacetone will be produced). Traces on the instrument wall can be removed by cleaning with cleaning solution.

Washing contraindications

1. When cleaning the instrument with normal methods, wash your hands with soap first, so that the oil on your hands will adhere to the instrument, which increases the difficulty of cleaning. If the instrument is stored in dust for a long time, first wash it with clean water, and then use detergent to wash or clean it as required. If decontamination powder is used, apply a small amount of decontamination powder on the brush, brush the inside and outside of the instrument again, and then rinse with water until the decontamination powder is not visible to the naked eye. Rinse with tap water for 3-6 times, and then rinse with distilled water. More than three times. A fine glass instrument should be able to hold water droplets. If you can still hang water droplets, you still need to wash them again. When flushing with distilled water, use a smooth wall flushing method and fully shake. The instrument flushed with distilled water shall be neutral to the indicator.

2. The glass instrument for trace metal analysis shall be soaked in 1:1~1:9HNO3 solution, and then washed normally.

3. During fluorescence analysis, the glass instrument should not be washed with washing powder (because the washing powder contains fluorescent whitening agent, which will bring errors to the analysis results).

4. When analyzing carcinogens, appropriate soaking and soaking should be used, and then washing should be carried out according to the usual method.


Common drying methods

The instruments used in chemical experiments usually need to be dry and clean. The presence of water sometimes affects the rate of chemical reactions, and sometimes even makes chemical reactions impossible. For experiments with general anhydrous requirements, simply use the instrument to dry and use. For anhydrous experiments, dry the instrument in an oven or hot air dryer. In case of emergency use, clean the instrument with a small amount of ethanol or acetone, and then dry it with a hair dryer. It must be specially pointed out that no matter what method is used to dry the instrument, it must be taken out when the instrument is cooled to room temperature, otherwise, when the hot instrument is cooled, the water will condense on the wall.

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

1. Drying is not urgent, and general drying is required. After washing in pure water, it can be inverted and dried in a dust-free place, and then dried naturally. The instrument can be placed on a shelf with diagonal nails and in a glass cabinet with ventilation holes.

2. Dry and clean the instrument to control the humidity, and dry it in an electric oven at 105-120 ° C for about 1h. It can also be dried in an infrared lamp drying oven. This method is applicable to general instruments. The weighing bottle used for weighing, etc. is dried and placed in a dryer for cooling and storage. When drying with thick glass stoppers and thick wall instruments, pay attention to heating slowly, and the temperature should not be too high to avoid cracking. The measuring device shall not be baked in the oven.

Hard tubes can be dried with an alcohol lamp. It should be baked from the bottom, and the tube mouth should be downward to prevent water droplets from flowing backward and bursting the tube. When there is no water drop during baking, the tube mouth moves upward to remove water vapor.

3. For the instrument that is in a hurry to dry or the larger instrument that is not suitable for putting into the oven, the hot (cold) air blowing element analyzer can be used for drying, usually using a small amount of ethanol, acetone (or later using ether), and then blowing with cold air for 1-2 minutes. When most of the solvent volatilizes, blow hot air to dry it completely, and then blow the residue with cold air. The steam stops it from condensing in the container. This method requires good ventilation to prevent poisoning andg, and does not contact open fire to prevent organic solvent explosion.


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

Accurately, the glass instruments cannot be dried in an oven, and the glassware that can be placed is used for holding rather than measuring. For example, beakers, flasks, and round bottom flasks are suitable for drying, and the gauges (with scales) of glass products are not suitable for drying. To be exact, glassware cannot be dried in the oven, and glassware that can be placed is used for storage rather than measurement. For example, beakers, flasks and round bottomed flasks are suitable for drying, while gauges (with scales) for glass products are not suitable for drying.

The temperature of dry glass is not too high. The temperature should be 100 degrees or less. Wear heat resistant gloves carefully to prevent scalding. In addition, it is better to keep the oven temperature below 45 ℃ (or normal temperature) and remove the instrument at high temperature. Prevent glass from cracking due to quenching and sudden heating.