Tag: beginner

How to Break and Insert Glass Tubing Safely in the Lab

Summary
Cutting glass tubing and inserting glass into rubber or cork stoppers are common tasks in teaching labs, but they are also a frequent cause of hand injuries. To work safely, always score and wet the glass before breaking it, wrap it in a towel or tissue when snapping, lubricate the end before insertion, and hold the glass close to the stopper while rotating gently. Never push hard on un-scored glass or hold the far end of the tube while forcing it through a stopper.

Glass tubing, thermometers and adapters are used everywhere in an organic lab. Preparing them correctly is routine work, but doing it carelessly can send broken glass into the palm of your hand. This article explains safe, step-by-step methods for breaking glass and inserting it into stoppers.

1. Why these tasks cause so many injuries

Typical injury patterns include:

  • Trying to snap un-scored glass tubing by brute force;
  • Holding the far end of a thermometer or tube while pushing it through a tight stopper;
  • Handling glass with bare hands when it suddenly breaks.

The common feature is poor control over where the force goes. Safe techniques help you control the break and keep your hands behind the line of force.

2. How to break glass tubing safely

2.1 Tools and preparation

You will typically need:

  • A glass file, glass-cutting tool or triangular file;
  • A drop of water or glycerol;
  • A towel or several layers of paper tissue.

2.2 Step-by-step procedure

  1. Mark the length you need on the glass.
  2. Score a small, clean line around the tube at that point using the file. You do not need to cut deeply; one firm stroke is usually enough.
  3. Wet the score line with a drop of water to help the crack start smoothly.
  4. Hold the tube with both hands, wrapped in a towel or paper tissue, with your thumbs placed opposite the score line.
  5. Gently bend the glass away from the score until it snaps along the line.

Do not twist or crush the glass. The force should be slow and controlled.

2.3 After the break

  • Smooth any sharp edges with fine sandpaper or a fire-polishing step if your instructor allows it.
  • Dispose of unwanted off-cuts in the broken-glass container, not in normal trash.

3. How to insert glass into rubber or cork stoppers

3.1 Why this step is risky

When you push a long piece of glass through a tight stopper, the stress concentrates near the point where it enters the stopper. If the glass breaks, the broken end can be driven toward the hand that is pushing.

3.2 Safer technique

  1. Lubricate the end of the glass with a drop of water or glycerol.
  2. Hold the stopper in one hand.
  3. With the other hand, hold the glass close to the end that enters the stopper, not at the far end.
  4. Push the glass in while rotating the stopper gently, applying slow, even pressure.
  5. Stop if resistance is very high and ask for a larger bore hole or a different adapter.

Never use sudden, strong force. Never hold the glass far away and “ram” it through.

4. Inspecting and using prepared glass

After you have prepared your glass:

  • Check that the exposed ends are reasonably smooth and free of large chips.
  • Make sure the glass sits straight in the stopper or adapter; avoid forcing it into distorted angles.
  • Handle long assemblies carefully and support them with clamps where appropriate.

5. Checklist: before, during and after

Before

  • I have the right diameter of glass tubing or thermometer.
  • I have a file, lubricant, and towel or tissue ready.
  • I know exactly how long the piece needs to be.

During

  • I always score before breaking glass.
  • I wrap the glass and keep my hands behind the line of force.
  • I hold glass close to the stopper end when inserting and rotate gently.

After

  • Off-cuts go into the broken-glass container.
  • Edges are smoothed if necessary and allowed by the lab.
  • Completed assemblies are handled and clamped carefully.

6. Safety note

Information on ChemNorth is for educational purposes and small-lab guidance. Always follow your institution’s safety rules and local regulations, and ask your instructor or safety officer if you are unsure about a procedure.

How to Use Heat Safely in an Organic Chemistry Lab

Summary
Heating is essential in organic chemistry, but it is also one of the main sources of fires and burns in the lab. To use heat safely, avoid open flames around flammable solvents, prefer hot plates and heating mantles, keep solvent bottles and waste containers away from hot surfaces, and never leave an active heater unattended. Always check glassware for cracks before heating and allow hot equipment to cool before moving or cleaning it.

When you begin experimental organic chemistry, you quickly discover that many reactions and procedures require heat. Refluxing, distillation, evaporation, and drying all depend on controlled heating. At the same time, heating is closely linked to fires, burns, and broken glassware. This article gives you a practical guide to using heat with the lowest reasonable risk in a teaching or small organic lab.

1. Why open flames are rarely a good idea

In an organic lab, open flames (Bunsen burners, alcohol lamps, lighters) are almost always the least safe heating option.

1.1 Flammable vapours travel farther than you think

  • Many organic solvents (diethyl ether, pentane, hexane, acetone, etc.) have low boiling points and high vapour pressures.
  • Their vapours are often heavier than air and can flow along the bench or near the floor.
  • A flame several metres away can still ignite a vapour cloud that drifts past it.

Because of this behaviour, many organic labs adopt a simple rule:

No open flames when flammable solvents are in use.

1.2 When a flame might still appear

If your lab still uses Bunsen burners, they are usually reserved for:

  • Briefly flaming glassware to dry it;
  • Sterilisation in microbiology work (less common in organic labs).

Even in these cases, flames should be used far from solvent bottles and waste containers, and only when your instructor confirms it is safe.

2. Safer options: hot plates and heating mantles

Hot plates and heating mantles remove the naked flame, but they are not risk-free.

2.1 Hot plates

Hot plates are good for:

  • Gentle heating of beakers and flasks;
  • Combining heating and magnetic stirring.

Safer habits:

  • Use appropriate support: place flasks in a beaker or on a ceramic pad when needed, not directly on bare metal if the design does not allow it.
  • Keep the area around the hot plate clear of solvent bottles, paper towels, and plastic items.
  • Turn the control to low or off before plugging in or unplugging.

2.2 Heating mantles

Heating mantles are designed to heat round-bottom flasks more evenly than hot plates.

Safer habits:

  • Use a mantle that fits the flask size properly; avoid “cramming” a larger flask into a smaller mantle.
  • Always support the flask with a clamp and stand, not just resting in the mantle.
  • Do not let liquid overflow into the mantle. If it happens, turn off the power and report it.

Quick question

You finish a reflux experiment and turn off the heating mantle. The round-bottom flask is still very hot and contains flammable solvent. What is the safest thing to do next?

  1. A. Immediately remove the flask from the mantle with bare hands so it cools faster.
  2. B. Leave the flask supported and let it cool in place before handling it.
  3. C. Move the hot flask quickly to another bench to free the mantle.
Show suggested answer

Leave the flask supported and let it cool in place before handling it.
Hot glassware can cause burns and is more likely to break if moved while very hot. Keeping the flask clamped and supported reduces the chance of spills or sudden breakage while the solvent and glass cool down.

3. Preventing fires when heating solvents

Most heating-related fires share a few common features. You can avoid many of them by planning ahead.

3.1 Keep flammable liquids away from hot surfaces

Before you turn on any heater, check:

  • Are solvent bottles stored away from the hot plate or mantle?
  • Is your waste container located somewhere cooler and safer?
  • Is there any spill or residue on the hot surface from a previous user?

If a spill occurs:

  • Turn off the heater if it is safe to do so.
  • Allow the surface to cool if necessary.
  • Wipe the area carefully with appropriate materials, disposing of them as chemical waste if required.

3.2 Control boiling and bumping

Uncontrolled boiling can throw hot liquid out of the flask:

  • Use boiling chips or a stir bar when appropriate.
  • Start with a low heat setting and increase gradually.
  • Never fill a flask more than about half full for boiling or reflux.

4. Glassware and heat: avoiding cracks and burns

4.1 Check glassware before heating

Heating cracked or chipped glassware increases the chance of sudden failure.

Before you heat:

  • Inspect the rim, body, and any joints for cracks or chips.
  • Do not use flawed glassware, especially under reflux, distillation, or vacuum.

4.2 Handling hot glassware

Hot glass often looks exactly like cold glass.

  • Assume glassware on or near heaters is hot.
  • Use heat-resistant gloves or tongs when moving recently heated items.
  • Allow glass to cool on a heat-resistant surface before washing or storing.

5. Checklist: heat safety before, during and after

Before, during and after using heat, you can use this quick checklist:

Before heating

While heating

After heating

6. Safety note

Information on ChemNorth is for educational purposes and small-lab guidance. Always follow your institution’s safety rules and local regulations, and ask your instructor or safety officer if you are unsure about a procedure.

Mini quiz

Which situation is most clearly unsafe in an organic chemistry lab?



Show suggested answer

Placing an open bottle of diethyl ether next to a hot plate that is turned on.
Diethyl ether is a very volatile and highly flammable solvent. Its vapours can travel to the hot surface and ignite, even if the flame or heating element is not in direct contact with the liquid. The other two situations are normally acceptable in a well-managed lab.