Laboratorinių stiklinių indų valymo, džiovinimo ir naudojimo paaiškinimai

This article provides a detailed explanation of the cleaning, drying, and usage methods for laboratory glassware. It is divided into three parts to facilitate understanding and application.

I. Cleaning of Glassware

1. Shaking Water Wash

Basic explanation of the shaking water wash method.

2. Brushing for Stubborn Stains

If there are substances on the inner wall that are not easily removed, use a brush to clean. The process involves:

• Disposing of the waste liquid first.
• Adding half the amount of water.
• Selecting an appropriate brush and holding it correctly to scrub.
• Repeat the process as necessary until the glassware is thoroughly cleaned.

Cleaning Illustration: (image labeled “Washing 2.1.png”)

3. Final Rinse

After brushing, rinse the glassware by shaking it several times with water. If necessary, use distilled water to rinse three times. In a clean state, the water will spread evenly without forming droplets (as shown in the left image), whereas in an unclean state, water droplets will remain on the surface (as shown in the right image).

If the glassware contains water-insoluble substances like alkalis, carbonates, or basic oxides, add hydrochloric acid first to dissolve them, then rinse with water. If grease or oil is present, use hot sodium carbonate solution followed by brushing. Alternatively, use a brush with a small amount of detergent. For narrow-necked instruments that are difficult to brush, rinse with a small amount of aqua regia or chromic acid solution. If these methods still fail, soak the item in a more concentrated solution and then rinse with water.

Safety Tip: Always dispose of waste liquid before adding water, and avoid cleaning multiple test tubes simultaneously.
Additional Safety Reminder: When handling corrosive solutions such as hydrochloric acid or aqua regia, wear protective gloves and goggles to prevent skin or eye injury.

II. Drying of Glassware

1. Air Drying (Left Image) vs. Oven Drying (Right Image)

Explanation of natural air drying and oven drying methods.

2. Blowing Dry (Left Image) vs. Heated Drying (Right Image)

Explanation of using compressed air and heated air for drying.

3. Airflow Drying (Left Image) vs. Rapid Drying (Right Image)

Explanation of airflow-based drying and rapid drying techniques.

Illustration Suggestion: Consider adding clear diagrams or photographs of each drying method to help users better understand the differences and practical applications.

III. Use of Common Glassware

1. Graduated Cylinder and Measuring Cup

Explanation of the usage guidelines for measuring liquids with graduated cylinders and measuring cups.

2. Pipette

Pipette usage precautions include:

• Select a pipette of appropriate size based on the volume needed (e.g., for 1.5 ml of liquid, a 2 ml pipette is more accurate than a 5 ml one).
• When drawing liquid, insert the pipette into the solution to avoid drawing air, which could cause overflow.
• After removing the pipette from the liquid, wipe the outer wall with filter paper before dispensing the liquid.
• Do not draw solvent or solution directly from the bottle with the pipette. Any remaining solvent or solution should be disposed of as waste, not returned to the storage bottle.

Illustration Suggestion: Provide an image showing the correct and incorrect methods of pipette usage.

3. Burette

The operation steps include: cleaning → applying Vaseline → leak checking → filling with operating solution → venting the burette → titration.

Safety Tip: When using Vaseline for sealing, ensure that the solution is not contaminated, as this could affect the accuracy of titration.

4. Volumetric Flask

Before using a volumetric flask, check whether its stopper leaks. A qualified stopper should be secured around the bottle neck and should not be replaced arbitrarily. If water droplets remain above the calibration mark on the inner wall, it can affect accuracy, so the flask must be thoroughly cleaned. Any solid substances to be weighed must be dissolved in a small beaker first, then transferred to the volumetric flask after cooling to room temperature. The flask should never be heated or dried in an oven.

Illustration Suggestion: Add an image demonstrating the correct technique for mixing the solution in the volumetric flask.

Additional Tip: Ensure that all volumetric operations are performed at room temperature to maintain solution accuracy.