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Glassware is used frequently in testing tasks and is also a commonly used and easily damaged consumable in laboratories. In daily work, being familiar with the operating procedures and precautions for various glass instruments not only helps to ensure efficient work performance but also enables the laboratory to avoid risks and reduce losses. I. Table of Instructions for Common Glassware Name Main Uses Precautions for Use Beaker: Used for preparing solutions, dissolving samples, etc. When heating, it should be placed on an asbestos net to ensure even heating; it should generally not be heated until dry. Erlenmeyer Flask: Used for heating samples and in volumetric titrations. In addition to the precautions mentioned above, when heating a flanged Erlenmeyer flask, the stopper should be removed; for flasks with non-standard flanges, the original stopper should be used. Iodine Bottle: Used in iodometric analysis or other quantitative analyses involving volatile substances. Same precautions as above. Round (Flat)-bottomed Flask: Used for heating and distilling liquids. Direct heating should be avoided; heating should take place over an asbestos net or in various heating baths. Round-bottomed Distillation Flask: Used for distillation ； It can also be used as a small-scale gas generation reactor; the same principles apply. In a Kjeldahl flask, organic substances are digested and then heated on an asbestos mesh. The opening of the flask should not be directed at oneself or others. The flask should be rinsed with purified water, or with cleaning solution, to clean the instruments; plastic flasks should only be used for washing and cannot be used to store solutions, as these solutions may corrode the flask. Weak acids and bases are not a problem, but some organic substances may affect the flask. Measuring cylinders and measuring cups are used to roughly measure a certain volume of liquid; they cannot be heated, used to prepare solutions, or dried in an oven. When using them, the solution should be added to or removed from them along the walls. Flasks are used to prepare standard solutions or the solutions to be analyzed with accurate volumes; the stoppers fitted to them must remain those originally designed for them ； Those that leak cannot be used ； It cannot be baked in an oven, nor can it be heated with direct flame; heating in a water bath is allowed. Titration tubes (25, 50, 100 mL) – volumetric titration procedures ； Acidic and basic pistons must be the original ones ； Those that leak cannot be used ； Cannot be heated ； Alkaline solutions cannot be stored for long periods ； Basic tubes cannot be used with titrants that react chemically with rubber. Micro volumetric pipettes (1, 2, 3, 4, 5, 10 mL) – for micro or semi-micro analytical titration tasks, only piston-type pipettes are suitable ； The other precautions remain the same; automatic titration using an automatic burette ； For operations involving titrants that require protection from air, in addition to the requirements common to ordinary burets, it is important to store them as a set; furthermore, a double bulb for inflating air is needed. Pipettes cannot be used to accurately measure certain amounts of liquid, and they cannot be heated ； The upper end and tip must not be damaged. The graduated pipette is used to accurately measure various amounts of liquid. Similarly, the short-form weighing flask is used to determine loss on drying or as a reference for drying substances in an oven ； High-precision scales are used for weighing standards; samples cannot be baked with a tightly sealed stopper, and the original stoppers must be used. Reagent bottles include flask-type bottles and jar-type bottles, with flask-type bottles being used for storing liquid reagents ； Wide-mouth bottles are used to contain solid reagents ； Brown bottles are used to store reagents that decompose easily when exposed to light and cannot be heated ； Solutions that release a large amount of heat during preparation must not be prepared inside the bottle ； The ground glass stopper should remain the original one ； Bottles used for storing alkaline solutions should be fitted with rubber stoppers to prevent them from becoming difficult to open over time. The reagents that need to be added using droppers follow the same rules. There are long-necked funnels and short-necked funnels; long-necked funnels are used for quantitative analysis and for filtering precipitates ； Short-necked funnels are used as ordinary filtering funnels; liquids can be added during experiments. When in use, it is important to ensure that the tip of the funnel is below the liquid surface, so as to prevent the gases generated from escaping through the funnel. Separatory funnels: used for dropping drops of liquid; available in spherical, pear-shaped, and cylindrical forms, and serve to separate two immiscible liquids ； Used for extraction, separation, and enrichment (often pear-shaped) ； In the preparation reaction, liquids are added using spherical or dropper funnels; the ground-glass stoppers must be the original ones – funnels that leak cannot be used. Test tubes: ordinary test tubes and centrifuge test tubes are used for qualitative analysis to detect ions ； Centrifuge tubes can be used in a centrifuge to separate solutions from precipitates through centrifugation. Tubes made of hard glass can be heated directly over a flame, but they cannot be cooled rapidly ； Centrifuge tubes can only be heated in a water bath; Nessler tubes cannot be directly heated for colorimetric or turbidity analysis ； Non-standard flanged plugs must be used as originally specified ； Make sure to keep the tube walls transparent; do not use cleaning powder for washing them. Condenser tubes: there are straight, spherical, coiled types, as well as air condenser tubes. These are used to cool the liquid that has been distilled. Coiled tubes are suitable for condensing vapors of liquids with low boiling points, while air condenser tubes are used for condensing vapors of liquids with a boiling point above 150°C. They cannot be used for heat accumulation or release ； Note that cooling water should be fed in through the lower opening, while the upper opening is for water discharge. The suction filter flask, which receives the filtrate during filtration, is a thick-walled container capable of withstanding negative pressure ； Not heatable: Surface plates, lid, flasks, funnels, etc. cannot be heated directly over an open flame; their diameter should be slightly larger than that of the container they cover. Used for grinding solid reagents and samples in a mortar ； Substances that do not react with glass cannot be impacted ； It cannot be baked; the dryer is used to keep materials that have been dried or burned dry ； A small amount of the prepared product can also be dried by placing color-changing silica gel or other desiccants at the bottom, and applying an appropriate amount of vaseline to the sealed portion ； Do not insert red-hot objects; once hot objects are placed in, the lid must be kept open at all times to prevent it from popping off or to avoid difficulty opening it after it cools down. Filtration using a fritted glass funnel requires vacuum filtration ； Cannot gather cold or heat ； Cannot filter hydrofluoric acid, alkalis, etc ； Wash it immediately after use. For gravimetric analysis using fused glass crucibles, the precipitates to be weighed need to be dried as mentioned above. Standard jointed instruments are used in organic chemistry and organic semi-microanalysis for preparation and separation; no lubricant is required at the joints ； It must not be subjected to skewed pressure during installation ； It is necessary to purchase the required equipment in full. II. Methods for washing glass instruments: In daily work, washing glass instruments is not only a preparatory step before experiments but also a technical task. Whether glass instruments are washed properly affects both the accuracy and precision of the analysis results. 1. Washing of general glassware (such as test tubes, beakers, Erlenmeyer flasks, etc.). First, remove the residues from the container, rinse it with tap water until no dirt remains. If there is grease, wipe it off with absorbent paper first, then soak the container in a solution of laundry detergent for 10–15 minutes. After that, scrub it thoroughly with a brush of appropriate size, rinse it well with tap water, and finally rinse it 2–3 times with distilled water. Hot soapy water has stronger cleaning power and can effectively remove grease from utensils. Detergent and cleaning powder are difficult to rinse off completely, often leaving a layer of fine particles on the surfaces of containers; therefore, it is necessary to rinse them multiple times with water, or scrub them once with dilute hydrochloric acid followed by rinsing again with water. Finally, they should be dried in an oven or placed upside down in a clean area to dry before use. For properly washed glassware, no water droplets should remain on the walls; otherwise, it indicates that the ware has not been washed thoroughly and should be washed again using the aforementioned method. 2. Cleaning of glass instruments used for measuring (pipettes, pipettes for volume measurement, burettes, volumetric flasks, etc.). After each use, pipettes must be rinsed promptly with running water or immersed in cold water; especially after transferring viscous liquids such as whole blood, plasma, or serum, they should be thoroughly rinsed with running water to prevent the substances from drying out and clogging the pipette. Used pipettes are typically rinsed with tap water, then immersed in a 0.5% detergent solution or chromic acid solution for at least 4 hours; afterwards, they are thoroughly rinsed with tap water and flushed with distilled water, before being dried and set aside for use. Measuring glassware must not be baked; it can only be air-dried or left to dry naturally. 3. Cleaning of glass and quartz cuvettes: After use, cuvettes should be thoroughly rinsed with distilled water, then placed upside down in a clean area to dry before being used again. All cuvettes can be washed with a 0.5% detergent solution; they must be carefully cleaned using absorbent cotton, then thoroughly rinsed with plenty of distilled water, and dried by being inverted. Note: Cuvettes must not be cleaned with an ethanol solution of potassium hydroxide or other strong alkaline cleaning solutions, as this will cause severe corrosion of the cuvettes. 4. Slide and cover slip: Slides and cover slips should not be washed vigorously; they should be rinsed with clean water, soaked in chromic acid solution for 2–4 hours or boiled in dilute chromic acid solution for 0.5 hour. After that, they should be rinsed with clean water and stored in 95% ethanol. 5. Washing of toxic containers Containers contaminated with infectious samples, such as those containing viruses or serum from patients with infectious diseases, must be disinfected first before being washed and sorted. Containers that have held toxic substances, especially those containing highly poisonous drugs and radioactive isotopes, must undergo special treatment; only after it is confirmed that no residual toxins or radiation are present can they be cleaned for classification. Containers containing solid culture medium should first have the contents scraped off, and then be cleaned accordingly. 6. For the washing of crystals and precipitates in glass instruments, substances such as sodium hydroxide or potassium hydroxide that form carbonates by absorbing carbon dioxide from the air, as well as copper hydroxide or iron hydroxide precipitates which are difficult to clean, can be soaked in water for several days and then washed with dilute acid to convert them into substances that are soluble in water, after which they are rinsed with water. If organic deposits are present, they can be washed with boiled organic solvent or sodium hydroxide solution. 7. Cleaning of glassware contaminated with residual amalgam, grease, etc.: Mercury forms metal alloys (amalgams) with certain metals; these adhere to the glass walls, creating dark stains. The amalgam can be dissolved using a 10% nitric acid solution, after which the glassware can be rinsed thoroughly with water. If glass instruments contain residual dry oils, greases, or paint, they can be cleaned using ammonia or chloroform; unhardened greases can be cleaned with organic solvents ； Kerosene can be washed with hot soapy water ； Viscous oils can be washed by soaking in a hot sodium hydroxide solution. 8. Cleaning stains on glass instruments: The yellow-brown rust spots adhering to glass can be cleaned using hydrochloric acid solution ； The turbidity formed during the electrolysis of lead acetate can be washed away with acetic acid ； Brown manganese dioxide spots can be washed with ferrous sulfate, hydrochloric acid, or oxalic acid solution ； Ink stains on glass can be washed away with soda or sodium hydroxide solution. 9. Cleaning of silver salt stains remaining on glass instruments: Silver chloride and silver bromide stains can be removed using sodium thiosulfate solution, while silver mirror deposits can be eliminated by using hot dilute nitric acid solution, which converts them into water-soluble silver nitrate. III. Preparation of solutions for cleaning glassware. The most commonly used cleaning agents for glassware include soap, soap solutions (specialized products), laundry detergent, stain remover, cleaning liquids, and organic solvents. Detergent solutions, commonly referred to as cleaning solutions, come in various types depending on different requirements. The following are some of the more commonly used ones: 1. Strong acid oxidizing detergent solution – This type of solution is prepared using potassium dichromate (K2Cr2O7) and concentrated sulfuric acid (H2SO4). In acidic solutions, K2Cr2O7 possesses strong oxidizing power, and it has very little erosive effect on glassware. Therefore, this type of lotion is the most widely used in laboratories. The preparation concentrations vary, with various levels ranging from 5% to 12%. Preparation method: Take a certain amount of K2Cr2O7 (industrial grade is sufficient), heat it in water at a ratio of about 1–2 parts water per part of K2Cr2O7 until it dissolves. After it cools slightly, slowly add the required volume of industrial-grade concentrated H2SO4 to the K2Cr2O7 solution (under no circumstances should water or the solution be added to H2SO4). Stir continuously while adding the acid using a glass rod, being careful not to let any liquid spill. Once well mixed, allow the mixture to cool, then transfer it to a bottle for later use. The newly prepared cleaning solution is reddish-brown and has a strong oxidizing power. Note: When the cleaning solution turns black-green after being used for a while, it indicates that it no longer has an oxidizing cleaning effect. 2. Alkaline wash solution: Alkaline wash solutions are used to clean glass instruments contaminated with oils. These solutions are applied using a long-term immersion method (over 24 hours) or a boiling method. Note that when retrieving instruments from the alkali wash solution, latex gloves must be worn to prevent skin burns. Commonly used alkaline cleaning solutions include sodium carbonate solution (Na2CO3, also known as soda ash), sodium phosphate solution (Na3PO4), sodium dihydrogen phosphate solution (Na2HPO4), and others. 3. Organic solvents: For utensils with fatty stains, they can be scrubbed or soaked using organic solvents such as gasoline, toluene, xylene, propanol, alcohol, trichloromethane, and ether. However, using organic solvents as cleaning solutions is costly; for large instruments that can be cleaned with a brush, alkaline cleaning solutions should be used whenever possible. Organic solvents are used for cleaning only small parts or instruments with special shapes that cannot be cleaned with a brush, such as the inner holes of pistons, the tips of pipettes, the tips of burettes, the piston holes of burettes, droppers, and small bottles. IV. Drying and Storage of Glass Instruments 1. Drying of Glass Instruments (1) Air-drying: Glass instruments that are not needed immediately can be placed on instrument racks or in specialized cabinets to allow water to evaporate naturally; placing them upside down also helps to prevent dust accumulation. (2) Drying: The most common method for drying glass instruments is drying by heat; the cleaned glass instruments are placed in a clean oven at 110–120°C and baked for about 1 hour. Some ovens also use forced air to remove moisture. Dried glass instruments are generally cooled in the air, but volumetric flasks and glass instruments used for precise weighing should be cooled and stored in a desiccator. (3) Drying: Glass instruments that need to be used immediately or are difficult to dry can be dried using a hair dryer. A hair dryer can produce cold and hot air. Various colorimetric tubes, centrifuge tubes, test tubes, Erlenmeyer flasks, beakers, etc. can be quickly dried using this method. Some glass instruments that are not suitable for drying at high temperatures, such as pipettes, burettes, and hydrometers, can also be dried using a hair dryer. If glassware contains a large amount of water, it can be rinsed first with acetone or ethanol; if necessary, it can then be rinsed with ether, after which it can be dried quickly. (4) Measuring glass instruments should be allowed to drain naturally; they must not be baked in an oven. 2. Storage of glass instruments: They should be stored in test cabinets in a categorized manner, placed securely, with taller and larger glass instruments kept inside.