Category: Lab Safety & Environment

Fundamental skills before doing experiments: using a laboratory notebook, pre-lab preparation, percent yield calculations, and finding reliable pre-lab information.

An Advanced Lab Guide: Three-Neck, Four-Neck, or Claisen Adapter?

In organic synthesis, interface economics matter. We break down when to rely on a classic three-neck flask, when to use a Claisen adapter, and why investing in a four-neck flask is the professional upgrade your reaction setup needs.

Is Your Reaction Setup Smart Enough?

In an organic synthesis laboratory, assembling a reaction apparatus is not unlike performing delicate surgery. As experiments evolve from simple, single-step reactions into multi-task systems—requiring simultaneous heating, stirring, controlled addition, temperature monitoring, and inert gas protection—one inevitable question arises:

Do I still have enough ports?

I’m ChemNorth, someone who spends a lot of time working with glassware and reaction setups. Today, we’ll set reaction mechanisms aside and talk about something far more practical: the economics of interfaces. When should you rely on a classic three-neck flask, improvise with a Claisen adapter, or step up to a dedicated four-neck flask?

1. The Classic Choice: The Three-Neck Flask — Adequate, but Restrained

For most teaching laboratories and straightforward reflux reactions, the three-neck round-bottom flask is a dependable workhorse. Its roles are clearly defined:

  • Left neck: Condenser for reflux
  • Center neck: Mechanical stirrer or thermometer—the heart of the reaction
  • Right neck: Addition funnel or stopper

Its limitation lies precisely in its simplicity. When a reaction requires simultaneous reflux, temperature monitoring, slow addition, and inert gas protection, three ports quickly feel insufficient. Any temporary removal of a joint risks introducing air or moisture—often undoing hours of careful preparation in a single moment.

2. Creative Improvisation: Three-Neck Flask + Claisen Adapter

This is where many experienced chemists reach for a familiar rescue tool: the Claisen adapter. By splitting one joint into two, it instantly expands your available interfaces.

Is it clever? Absolutely.
Is it ideal? Not quite.

Advantages

  • Flexible and cost-effective
  • Quickly solves interface shortages without replacing core glassware

Trade-offs

  • Top-heavy assemblies: Stacked adapters raise the center of gravity. Under vigorous stirring, the setup can become unstable—more “bobblehead” than bench-safe.
  • Hidden dead volume: Complex internal channels trap condensate, complicate cleaning, and can negatively impact yields for volatile or precious products.
  • More joints, more risk: Every additional ground-glass connection increases the chance of leaks—particularly problematic for high-vacuum or air-sensitive work.

Claisen adapters are a smart contingency plan—but rarely the best long-term solution.

3. The Professional Upgrade: Four-Neck Flasks, Designed for Complexity

When experimental demands increase, a purpose-built four-neck round-bottom flask doesn’t just add one more port—it fundamentally changes how you work.

Why is it the professional choice?

True Parallel Operation

Each neck can be permanently assigned—reflux, temperature probe, addition funnel, inert gas inlet or pressure control—without ever disassembling the system. The reaction remains sealed, controlled, and undisturbed throughout the entire process.

Design with Intent

Well-designed four-neck flasks (such as those in the Laboy series we trust) feature side necks angled at approximately 20°. This is not cosmetic. The geometry naturally separates condensers, funnels, and probes, preventing crowding and making adjustments intuitive rather than awkward. In contrast, Claisen-stacked assemblies often feel congested and unwieldy.

Stability Through Integration

A one-piece structure lowers the center of gravity and distributes mechanical stress more evenly. Combined with heavy-wall glass construction, four-neck flasks handle extended reflux, thermal cycling, and demanding conditions with greater confidence. This is a level of stability no modular workaround can truly replicate.

Decision Time: One Table, Clear Answers

Experimental Scenario Recommended Setup Core Reasoning
Teaching labs, simple reflux Three-neck flask Simple, economical, and easy to clean—ideal for foundational laboratory work.
Occasional multifunction use, strict budget Three-neck flask + Claisen adapter A temporary workaround that trades stability and sealing performance for flexibility.
Multi-step synthesis, air- or moisture-sensitive reactions, high vacuum Four-neck flask ChemNorth’s top recommendation: a stable, integrated platform that lets you focus on chemistry, not glassware improvisation.

A Final Thought

In the laboratory, good equipment is more than a tool—it is an extension of your thinking. If you find yourself repeatedly running out of ports and building increasingly acrobatic glass assemblies, it may be time to rethink the approach.

Investing in a well-designed four-neck flask is often one of the most cost-effective upgrades a synthetic chemist can make. It shifts your attention back to where it belongs: the chemistry itself, not a balancing act of adapters and clamps.

Let your experiments be about discovery—not about wrestling with glass.

When should I choose a four-neck flask over a three-neck flask?

You should upgrade to a four-neck flask for multi-step synthesis, air-sensitive reactions, or when using high vacuum. It offers better stability and allows for dedicated ports for probes and inert gas without needing adapters.

What are the disadvantages of using a Claisen adapter?

Claisen adapters can make the setup top-heavy and unstable. They also add dead volume which is hard to clean and increase the risk of leaks due to the extra glass joints.

Is a three-neck flask enough for standard reflux reactions?

Yes. For teaching labs and simple reflux reactions, a three-neck flask is a dependable and economical choice.

Why Your Vigreux Column Failed: A Glassblower’s Guide | ChemNorth

Article Body

(Intro) A Vigreux column adds surface area, not controllable theoretical plates—and without proper thermal management, it rarely performs the way people expect.

Common Misconceptions: Is Your Vigreux Column Defective?

I’ve been blowing scientific glass for nearly twenty years, and over that time I’ve seen almost every kind of request imaginable. Last week, a long-time client from a local research institute came to my workshop with a Vigreux column I had made.

He pointed at the indentations and asked, “Is there a defect in this column? I’ve seen other brands where the spikes are much denser. Yours seem too sparse. My distillation purity was poor yesterday, and I suspect this column doesn’t provide enough theoretical plates.”

I held the column up to the light. It was a standard Vigreux structure—uniform wall thickness, consistent indentation depth and angle, no visible stress or flaws. There was nothing wrong with the glass itself.

I told him, calmly, “The column isn’t defective. Even if I rebuilt this to look like a hedgehog, your separation probably wouldn’t improve. The effectiveness of a Vigreux column has never depended on how many ‘teeth’ it has.”

That conversation reminded me how often even experienced chemists misunderstand the limitations of the glassware they use every day. From a glassblower’s perspective, here’s why a Vigreux column so often feels like it “isn’t working.”

Recommended Reading: For a clear visual comparison of how Vigreux, packed, and other fractional distillation columns are constructed internally, see our guide: 👉 Inside Fractional Distillation Columns: What’s Really Inside?

The Glassblower’s Perspective on Design

When customizing laboratory glassware, many people assume:

  • More complex structure → More surface area → Better separation.

That intuition isn’t wrong—but it’s incomplete.

Vigreux Columns
Hemple Packed Column

Surface Area vs. Turbulence

The inward-facing indentations of a Vigreux column serve only two real functions:

  1. Increase Contact Area: They increase gas–liquid contact area.
  2. Create Turbulence: They disrupt straight vapor flow and introduce turbulence.

What they do not do is magically generate a large number of theoretical plates. By design, a Vigreux column is a low-efficiency fractionating column. If your target separation demands high plate counts, asking for more indentations misses the point. At that stage, you should be using a Packed Column, not trying to force extra performance out of a Vigreux.

Why More Indentations Reduce Efficiency

The next question I’m usually asked is: “If you add more rows of indentations, wouldn’t that help?”

In practice, it often does the opposite. From a glassblowing standpoint, indentation density is limited by the need to maintain uniform wall thickness and manage thermal stress. However, overcrowding the internal structure introduces a more serious operational issue.

The Risk of Column Flooding

When vapor flow is partially obstructed by overly dense spikes, refluxing liquid can no longer drain smoothly downward. Instead, liquid becomes trapped and pushed upward by rising vapor. This phenomenon is known as Flooding.

When flooding occurs:

  • Gas–liquid contact turns chaotic.
  • Pressure drop increases significantly.
  • Effective fractionation collapses.

In extreme cases, the distillation stalls entirely. At that point, separation efficiency isn’t just poor—it’s fundamentally compromised.

The Real Culprit: Lack of Insulation & Thermal Management

If the column itself wasn’t the problem, what went wrong with my client’s experiment? I asked one simple question:

“When you ran the column, did you insulate it?”

There was a pause. “You mean dressing it? No—I wanted to see the liquid level.”

That answer explains most disappointing Vigreux results I encounter.

Understanding Internal Reflux

In my experience, the majority of “inefficient” Vigreux columns aren’t failing because of poor glass design. They fail because of poor insulation.

Vigreux columns are thin-walled by necessity. Without insulation, ambient air strips heat from the rising vapor long before it reaches the still head. This creates excessive, uncontrolled internal reflux. While some reflux is essential, reflux driven by room temperature rather than operator control rarely improves separation.

I advised him to try again: wrap the column with glass wool or cotton, or use a vacuum-jacketed alternative. Let vapor travel smoothly to the top, where the reflux ratio can be managed intentionally rather than dictated by heat loss to the lab.

Glass Vigreux distillation column wrapped in white cotton insulation to prevent heat loss, connected to a round bottom flask in a heating mantle.
The Solution in Action: A Vigreux fractional distillation column fully wrapped in insulation material (lagging). This setup illustrates the practical solution for maintaining adiabatic conditions, preventing premature condensation, and ensuring vapor reaches the condenser—crucial for high-boiling point distillations.

3 Expert Tips for Better Distillation Results

Two days later, I received a message: the desired purity had been reached. After decades at the torch, I’d offer three practical recommendations to anyone working with fractional distillation columns:

1. Communicate with Your Glassblower

Before assuming an instrument is defective, discuss the problem. Often the solution isn’t a new column—it’s an extra layer of insulation or a slight adjustment in technique.

2. Choose the Right Tool

Vigreux columns are meant for simple separations. If your components boil within about 10 °C of each other, stop struggling with a Vigreux and switch to a higher-efficiency design, such as a Packed Column.

3. Respect the Physics

Glass geometry is static. Heat input, insulation, and reflux control are not. Focus on the system as a whole, not just the shape of the glass.

Remember: Glass doesn’t decide how well your distillation runs. You do.

FAQ: Common Questions About Vigreux Columns

Q: What is the main disadvantage of a Vigreux column? A: The main disadvantage is its relatively low number of theoretical plates compared to packed columns. It is not suitable for separating compounds with very close boiling points.

Q: Why is my Vigreux column flooding? A: Flooding usually occurs when the vapor velocity is too high or the indentations are too dense, preventing the liquid from draining back down. It can also happen if the heat input is too aggressive.

Q: Do I need to insulate my Vigreux column? A: Yes, absolutely. Without insulation (like glass wool or a vacuum jacket), ambient air cools the vapor too quickly, causing uncontrolled internal reflux and reducing separation efficiency.

About the Author: Zoe.W

With over 20 years of experience in hand-blown glass manufacturing, Zoe.W is dedicated to bridging the gap between craftsmanship and laboratory application. Combining frontline lab feedback with deep industry knowledge, she specializes in solving complex equipment challenges for organic chemistry experiments.

Connect with Zoe: Email |

Inside a Fractional Distillation Column: A Visual Guide to 4 Lab Types

Hemple Packed Column
Vigreux Columns
Laboy Glass Snyder Distillation Column With 24/40 Joints 300mm In Overall Height
Bulb-type Columns
Spinning Band Columns

From the outside, a fractional distillation column doesn’t look like much. It’s usually just a piece of glass or metal sitting between a boiling flask and a condenser. But if you’ve ever tried to separate two liquids with similar boiling points, you find out quickly that what happens inside the column matters a lot.

Textbooks usually show a single generic drawing and call it a day. In real laboratories, however, a “fractional column” can refer to several very different designs, each with its own internal structure and personality.

This article looks inside the four types of lab-scale fractional columns you’re most likely to encounter:

  • Vigreux columns
  • Packed columns
  • Bulb-type (Hempel-style) columns
  • Spinning band columns

We aren’t looking at equations here. We are looking at the physical reality: What does it actually look like inside, and what does that mean for your separation efficiency?

1. Vigreux Columns: The “Teeth” Design

Vigreux Columns

A Vigreux column is often the first fractional column a student handles. If you hold it up to the light, the internal structure is immediately obvious.

Instead of a smooth bore, the inner wall features rows of glass indentations pressed inwards. They look like little “teeth” or steps sticking into the center of the column.

Key Features:

  • No loose packing
  • No trays
  • No moving parts

How it works: During a distillation, vapor rises from the boiling flask into the column. The cooler glass teeth provide surface area for vapor to condense. This condensate forms a thin film and runs back down the column as reflux.

Each of those teeth acts as a small interruption in the vapor’s journey upward. The continual condensation and re-evaporation along the wall gives you more effective separation than a simple straight adapter, without making the hardware complicated.

The Verdict: Vigreux columns are tough, easy to clean, and forgiving to beginners. The trade-off is that their separation efficiency is modest compared to more specialized designs.

If you’re curious why the familiar “teeth” design adds less separation than many people expect, we take a closer look here:
→ Why Vigreux Columns Are Less Efficient Than they Look

2. Packed Columns: Maximizing Surface Area

Hemple Packed Column

From the outside, a packed column can look almost identical to a plain glass tube. The difference is obvious once you look through the bore: it’s full of packing material.

What’s Inside: Inside, you’ll find small pieces of material designed to maximize surface area, such as:

  • Glass helices or Raschig rings
  • Glass or metal saddles
  • Metal or PTFE mesh rolls

A support at the bottom—usually a frit, a perforated plate, or a plug of glass wool—keeps the packing from falling into the flask.

How it works: When a packed column is running, hot vapor rises through the small channels between packing pieces, while liquid flows downward over the surfaces. Every bit of that surface becomes a site for vapor–liquid contact.

The column doesn’t look “empty” from the inside. It feels more like a dense maze of surfaces coated with thin liquid films, with vapor squeezing through the gaps. That huge internal area is what gives packed columns their high efficiency (often measured in HETP – Height Equivalent to a Theoretical Plate).

The Verdict: The price you pay is sensitivity. Push the heat too hard or let too much liquid accumulate, and the packing can flood, causing pressure drops and performance collapse. Cleaning is also more difficult than with a simple Vigreux tube.

3. Bulb-type (Hempel) Columns: Visualizing the Process

Laboy Glass Snyder Distillation Column With 24/40 Joints 300mm In Overall Height
Bulb-type Columns

Bulb-type, or Synder-style, fractional columns are less common in modern catalogs but remain very popular in teaching and small-scale organic labs.

Looking inside one, you don’t see teeth or loose packing. Instead, you see a vertical chain of glass bulbs joined by narrower necks. Each bulb acts as a small chamber where vapor can expand and liquid can temporarily pool.

How it works:

  1. Vapor enters a bulb, expands, and cools slightly.
  2. Part of it condenses and collects as a liquid layer.
  3. Overflow drains back down through internal paths to the bulb below.
  4. The remaining vapor continues upward to the next bulb.

From the outside, you can literally watch liquid appear and move inside the bulbs as the distillation runs. Each bulb behaves like a visible equilibrium stage. For teaching, this makes concepts like “reflux” and “plates” much less abstract.

The Verdict: Bulb-type columns sit in the middle ground: more effective than a short Vigreux column, but less extreme than optimized packed columns. They are a nice compromise when you want both performance and a clear visual picture of the process.

4. Spinning Band Columns: The High-Performance Choice

Spinning Band Columns

Spinning band columns are what you reach for when you’ve run out of easy options and still need higher resolution to separate close-boiling compounds.

At first glance, they appear to be long, narrow glass columns with a motor housing at the top. Inside the bore, however, is a complex mechanism:

  • A central shaft driven by the motor.
  • A flexible band (metal or PTFE) attached to that shaft, running the length of the column.

How it works: When the column is in use, the motor spins the band at high speed. As vapor rises and condenses on the cooler surfaces, the spinning band actively wipes the condensate into a very thin, uniform liquid film and drags it along the column interior.

Instead of relying on static packing or gravity, a spinning band column actively manages the liquid film thickness. This constant refreshing of the surface allows these columns to reach very high effective plate counts on the lab scale.

The Verdict: The downside is cost, complexity, and maintenance. You have moving parts, seals, and a drive mechanism. For routine teaching, they are overkill; for difficult separations of valuable materials, they are essential.

Quick Comparison: Which Column is Inside Your Lab?

Comparison of Vigreux, bulb-type, packed and spinning-band fractional distillation columns
Column Type Internal Feature Efficiency Complexity Best For
Vigreux Glass “teeth” along the inner wall Low Low Simple distillations, student labs
Bulb-type Series of glass chambers or bulbs Medium Low Visualizing reflux, teaching demonstrations
Packed Beads, mesh, or rings packed in the column High Medium General high-purity distillation work
Spinning Band Rotating helical band inside the column Very high High Close-boiling point separation, analytical work

This comparison is meant to help you recognize what is already sitting on your lab bench. If you are currently shopping for a new fractional distillation column, you may find this practical buying guide helpful: How to Choose the Right Fractional Distillation Column for Your Lab .

Summary: Different Interiors, Same Goal

Although these four designs look very different inside, they are all built around the same simple idea: Make vapor and liquid meet each other as many times as possible on the way up and down the column.

They just achieve this in different ways:

  • Vigreux: Fixed glass indentations.
  • Packed: A bed of small pieces with huge surface area.
  • Bulb-type: Visible chambers for partial equilibration.
  • Spinning band: A mechanically refreshed thin film.

There is no hidden machinery in a fractional distillation column – only surfaces, temperature gradients, and gravity working together.

Once you’ve seen how these interiors are built, many of the usual puzzles in distillation – such as [column flooding], [poor separation efficiency], or [strange temperature profiles] – start to make much more sense.

In practice, watching these columns at work does more to fix the concepts in your mind than any diagram ever will. ChemNorth is here to help bridge that gap between the drawing on the page and the glass in your hands.

How Ground-Glass Joints Are Made — From Glass Tubing to a Finished Joint

Most people first meet a ground-glass joint in the context of a finished piece of equipment: a condenser, a round-bottom flask, an adapter pulled from a drawer. The joint looks complete and inevitable, as if it has always existed in that shape.

But a ground-glass joint is not a given. It is something that has been formed, ground, corrected, checked and heated before it ever reaches your bench. To understand why some joints rotate with a soft, confident feel—and why others leak, grind, or seize—it helps to follow the joint back to where it begins.

How Ground-Glass Joints Are Made: From Glass Tubing to a Finished Joint

Process at a glance

Glass tubing
➜
Forming the body
➜
Coarse grinding
➜
Fine grinding
➜
Hand finishing
➜
Cleaning & inspection
➜
Stress relief & annealing
➜
Assembled into apparatus

Every joint begins as a simple length of borosilicate tubing. Someone has to decide where on that tube the joint will live, and what kind of body will carry it: a socket on a condenser, a cone on a flask, a sidearm on a distillation adapter.

At the forming stage, a lampworker or forming specialist heats and shapes the glass. On a lathe, the tube turns slowly in the flame while tools coax it into shape. At a hand torch, the glassblower builds up a more complex piece step by step. The goal here is quiet but strict: the part of the glass that will become the joint must be straight, centered and aligned with the rest of the piece. If this is wrong, a later grinding machine can still cut a perfect 1:10 taper—but that taper will sit crooked, and you will feel it every time you assemble the apparatus.

Close-up of a scientific glassblower heating a borosilicate flask over a blue torch, with the glowing standard taper ground joint held in a graphite clamp.

Once the body is ready, the joint blank moves to grinding. In many scientific glass factories over the past few decades, the philosophy has been simple: let the machines define the geometry, and let human hands perfect the seal.

The first machine pass is a coarse grind. Most of the excess glass is removed and the familiar 1:10 taper starts to appear. Diameters move toward their target values, and gauges or reference tools begin to come out. A second, finer pass then refines this taper and nudges the joint firmly into the tolerance band required for interchangeable glassware. After these two passes, the joint is, on paper, “correct”: it has the right taper angle, the right length, the right diameters at the reference points. It will fit into any other joint of the same nominal size.

What it does not yet have is character. The surface may still carry tiny high spots, faint circles or spirals from the grinding path, and a texture that is technically within spec but not yet pleasant to use. This is where machines hand the work back to people.

A specialist whose job may be almost nothing but joints takes over. A small amount of fine abrasive—silicon carbide or diamond—is introduced. Using a master gauge or a trusted mating joint, the worker searches for those minute irregularities the machine left behind. The pressure is light, the motion controlled. The aim is not to carve a completely new geometry, but to push this already-interchangeable joint toward the best version of itself: more even contact, smoother rotation, fewer opportunities for leaks.

This is very different from the old practice of grinding one specific male and one specific female together until they only worked perfectly as a pair. Here, the standard is still interchangeability. The joint must continue to fit any matching size from the same line. Hand finishing simply makes that fit more forgiving and more reliable.

Behind the scenes there is another layer of specialization. In many factories, one person or one team focuses on semi-finished joints: they pre-shape the taper, run the coarse and fine machine passes, and carry out the final hand finishing. Their output is a box of joints that are dimensionally correct, well behaved, and ready to be attached to something. Those semi-finished joints then make their way to the lampworker’s bench. The lampworker does not “fix the joint”; they decide how it lives inside the final instrument—at what angle, at what height, and with how much stress locked into the glass around it. A good adapter or condenser is therefore a collaboration: the taper you feel between your fingers is the work of the joint grinder, and the way that taper lines up in the apparatus is the work of the lampworker.

After grinding and forming comes cleaning, inspection and annealing. Abrasive residues must be removed, both for safety and to prevent further uncontrolled wear. Dimensions and taper are checked again. Finally, the piece passes through an annealing cycle that relaxes internal stress. Only then is the joint truly ready to face heating, cooling and mild vacuum in someone else’s lab.

How to Fix Common Ground-Glass Joint Problems in Everyday Lab Use

All of this factory work collapses, at the bench, into a few very simple questions: does this joint seal, does it turn smoothly, can I trust it in a setup that matters? The answers still come from the way the joint was formed, ground, finished and annealed—but in everyday use you mostly meet those decisions as small annoyances: a joint that always needs more grease, a condenser that tends to weep under mild vacuum, a flask that never quite feels “right”.

One of the main places where this shows up is the surface texture of the taper. A machine-ground surface, especially one produced with fixed-abrasive diamond wheels, tends to have directional marks: faint rings, shallow spirals, very fine ridges. When the process is well tuned, these marks are shallow and regular enough that they behave well. When it is not, they can become tiny leak paths, especially under vacuum, like microscopic threads running through what ought to be a seal.

Hand finishing breaks up this pattern. By removing small high spots and introducing a more random, finely frosted texture, it increases both the effective contact area and the tolerance of the joint to small imperfections. This is why two 24/40 joints can both be interchangeable and technically “within spec”, yet one feels immediately trustworthy and the other demands more grease, more force and more patience.

You can sense a lot of this with your own eyes and fingertips—how even the frosting looks, how clean the rim is, whether the taper feels straight when you sight along it, whether the joint seats with a quiet, controlled turn or with scratchy, hesitant movement. In Part 1 of this series we looked in detail at how to judge a good joint at a glance. Here, we will stay closer to the production side and look at what you can safely do at the bench when a joint is “almost good enough”, but not quite.

Factory-style fixes you can safely do at the bench

There are a few small, very controlled adjustments that borrow directly from factory practice. They will not turn a truly bad joint into a good one, but they can gently push borderline pieces back into the “reliable enough” category for routine work.

The first is the one that feels most like bringing the final finishing step back to your bench: using an extremely light lapping action to refine the surface.

PRACTICAL LAB TIP

Reviving a “tired” ground-glass joint

In everyday lab life you may inherit older glassware, or combine pieces from different manufacturers, and discover that a particular pair of joints always seems to be on the edge of leaking. If there are no cracks, no serious chips and no obvious distortion, you can sometimes improve their behaviour with a very gentle hand-lapping step.

How to do it:

  • Use a fine or extra-fine valve-grinding or lapping paste.
  • Apply a tiny amount to the taper.
  • Seat the matching joint and rotate slowly with light pressure.
  • Clean both pieces thoroughly to remove all abrasive, then test the fit.

The goal is to refine the surface, not to change the size or the taper angle. This kind of user-side lapping can help slightly worn or mixed-brand joints become more reliable, but it will not save joints with cracks, deep chips, badly distorted geometry or hidden stress — those are better retired than “rescued”.

A closely related trick is to deal with shiny, polished patches that sometimes appear on older joints. After years of use, grease and cleaning, a small area of the ground surface can become almost clear again. Under vacuum, that bright patch tends to behave like a tiny leak-prone island.

If the glass is otherwise sound, you can treat just that area with the same kind of very fine lapping paste, working gently over the whole taper so you do not create a step. The aim is not to “regrind” the joint, but simply to bring the surface back to a uniform, fine frost so the contact pressure redistributes. Once the bright spot has disappeared and the texture looks even again, you stop, clean thoroughly, and test. Very often, that is enough to move a marginal seal into the dependable range for routine work.

There is one more adjustment that comes straight from how glassworkers think about stress. A tiny chip right on the outer rim of a joint is more than a cosmetic flaw: it is a classic stress concentrator. In the factory, sharp edges are often given a slight chamfer to keep cracks from starting there.

At the bench, for very small chips at the outer edge only, some glassworkers will use a fine diamond file or stone to put the slightest, smooth radius on the damaged spot. The goal is again not to make it pretty, but to soften a razor-sharp edge into something less likely to grow into a larger crack the next time the glass is heated or knocked. This kind of micro-chamfer is only worth attempting on superficial damage far from the sealing area, and only for non-critical work. Anything deeper, closer to the ground surface, or associated with visible cracks is better retired than repaired.

These factory-style tweaks live right at the border between manufacturing and everyday use. If you are mainly worried about how to live with ground-glass joints in daily lab work—how to clean them without polishing the surface away, when and where to use grease, and what to do when a joint has seized completely—those belong to a different part of the story. On ChemNorth we cover those questions in two separate, practical guides:

Together, these small, factory-style adjustments sit in a narrow but useful space: they do not turn a fundamentally bad joint into a good one, but they can nudge a borderline piece back into the “reliable enough” category for everyday tasks—while the detailed “user-side” handling lives in those dedicated how-to articles.

Key Takeaways for Choosing and Using Ground-Glass Joints

If you prefer to think in checklists, you can summarize a good joint’s story in a single line:

formed straight → ground to the right taper → hand-finished for behaviour → cleaned, inspected and annealed → welded into the final piece without bending it

When you pick up a well-made joint, all of that is already behind you. What you are left with is the experience at the bench:

  • some joints seal beautifully with very little grease;
  • some grind, seize or leak even though the markings on the glass look right;
  • some pieces from high-end suppliers feel strangely “calm” in the hand compared with budget sets;
  • some joints survive years of heating and cooling, while others crack when pushed only a little.

None of this is random. It is the accumulated result of choices made at each stage from glass tube to finished joint.

In the first article of this series, we looked at why ground-glass joints are everywhere in organic labs and how to judge a good joint at a glance. In this second part, we have followed a joint back through forming, grinding, hand finishing and assembly to see how it becomes what it is.

The next natural question is about the numbers you see etched on the glass:

what do 14/20, 19/22 and 24/40 actually mean, and how should you think about size when you choose or design a setup?

That is the topic of the next article in this series.

👉 Read the next article:
Understanding Ground-Glass Joint Sizes: What 14/20, 19/22, and 24/40 Really Mean

How to Protect Your Skin from Chemicals in the Organic Lab


In an organic lab, you need to protect your skin from chemicals, not just your eyes and lungs. Many organic reagents can irritate or be absorbed through the skin, so hand protection is more than just a formality. To reduce risk, wear suitable gloves whenever you handle liquids or solids that could harm the skin, avoid touching door handles, phones or pens with contaminated gloves, and wash your hands thoroughly after removing them.

Skin contact with chemicals is one of the most common types of exposure in the organic lab. Sometimes the effects are immediate, like irritation or burns. In other cases, absorption through the skin may be slow and less obvious. This article focuses on practical habits and glove use that help you protect your skin in routine lab work.

1. How chemicals reach your skin

Common pathways include:

  • Direct splashes or spills during pouring, transferring or cleaning;
  • Handling contaminated glassware, benches or equipment;
  • Touching your face or hair with contaminated hands or gloves.

You cannot always control what a previous user has left behind, but you can control how you handle materials and how quickly you respond when something goes wrong.

2. When you should wear gloves

You should wear suitable protective gloves when:

  • Handling liquid organic reagents or solvents;
  • Working with corrosive or irritant chemicals;
  • Cleaning up spills or wiping contaminated surfaces;
  • Handling waste containers that may have residues on the outside.

You may not need gloves for every dry, solid material or for tasks like writing in your notebook, but when in doubt, ask your instructor.

3. Everyday habits to protect your skin from chemicals

To protect your skin from chemicals in everyday lab work, start with three habits…

3.1 Putting on and taking off gloves

  • Check gloves for holes or tears before use.
  • Pull them over the wrist so there is minimal gap between glove and lab coat sleeve.
  • When removing, peel them off from the wrist inside-out, avoiding contact with the outside surface.

3.2 Keeping gloves from spreading contamination

Gloves protect your skin, but they can spread contamination if you are not careful.

Avoid:

  • Touching door handles, phones, keyboards or notebooks with contaminated gloves;
  • Handling clean glassware or personal items while still wearing gloves;
  • Leaving gloves on when you have stopped working with chemicals.

Adopt a simple rule:

Anything you would happily touch with your bare hands should not be touched with contaminated gloves.

4. Responding to skin contact

If a chemical reaches your skin:

  1. Act immediately – do not wait to see whether it hurts.
  2. Rinse the affected area under running water for at least 10–15 minutes.
  3. Remove contaminated clothing or jewellery if possible.
  4. Inform your instructor or supervisor and follow the lab’s incident procedure.

For serious exposures, local emergency procedures always take precedence over any general advice.

5. Choosing gloves to protect your skin from chemicals

In many labs, nitrile gloves are the default choice because they resist a wide range of organic solvents better than natural latex. However, no single glove material is perfect for every chemical.

For now:

  • Use the glove type recommended by your lab or instructor for the chemicals you handle.
  • Do not assume that a glove is safe for all substances; permeation times vary widely.
  • Replace gloves promptly if they become torn, heavily contaminated, or if you have worked with aggressive solvents for a significant time.

Later on ChemNorth we will look at glove selection charts and material compatibility in more detail.

6. Checklist: skin protection in everyday work

Use this short checklist whenever you want to check whether you really protect your skin from chemicals during a lab session.

Before

  • I know which tasks require gloves today.
  • I have appropriate gloves available and they are intact.
  • My lab coat sleeves cover my arms.

During

  • I wear gloves when handling liquids and hazardous solids.
  • I avoid touching personal items and clean surfaces with contaminated gloves.
  • I change gloves if they become torn or heavily contaminated.

After

  • I remove gloves correctly and dispose of them in the proper container.
  • I wash my hands thoroughly with soap and water.
  • I report any skin contact that required rinsing.

7. 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 a Fume Hood Protects You in the Organic Chemistry Lab (and How to Use It Properly)

Summary
In an organic chemistry lab, a fume hood is a local exhaust device designed specifically to handle organic vapours, corrosive gases and hazardous dusts. You work outside the hood while your apparatus sits inside; the hood draws contaminated air away and discharges it safely. Using it correctly means knowing when to work inside the hood, how to set it up, and how to avoid turning it into a storage shelf.

1. What is a fume hood in an organic chemistry lab?

In an organic lab, a fume hood is a ventilated enclosure that provides local exhaust for hazardous air contaminants. It is designed so that:

  • You stand outside the hood.
  • Your glassware and apparatus are set up inside the hood.
  • Air flows from the room, past the front opening, through the hood, and out via a duct and fan system.

Typical features of a chemical fume hood:

  • A movable front sash (glass window) that you can raise or lower.
  • A work surface and interior lining made of materials resistant to chemicals and solvents.
  • Services inside the hood:
    • Water, gas and vacuum outlets
    • Electrical sockets
  • In many modern hoods:
    • Explosion-resistant lighting
    • Airflow indicators or alarms
    • Sometimes a digital face velocity display

Functionally, the purpose is simple:

Let hazardous vapours and gases “live inside the hood” and be exhausted, instead of entering your breathing zone or the rest of the lab.

2. What problems does a fume hood solve in organic work?

In organic chemistry, a fume hood primarily addresses four safety issues.

2.1 Preventing inhalation of organic solvent vapours

Many common solvents are volatile and hazardous to inhale, especially in poorly ventilated spaces:

  • Diethyl ether, THF
  • Dichloromethane, chloroform
  • Benzene, toluene, hexane, petroleum ether
  • Acetone and other ketones

Typical operations that should be done in a fume hood:

  • Distillation and reflux with volatile solvents
  • Concentrating solutions, rotary evaporation of larger volumes
  • Liquid–liquid extractions with volatile, toxic or smelly solvents
  • Pouring or transferring significant volumes of solvent

2.2 Reducing exposure to toxic or irritating gases

Certain reagents and reactions generate corrosive or toxic vapours, such as:

  • Acid fumes from hot HCl, HBr, HNO₃, H₂SO₄
  • Thionyl chloride (SOCl₂), POCl₃, oxalyl chloride, acid chlorides
  • Bromine, ammonia and other pungent gases

These can severely irritate the eyes and respiratory tract and may have systemic toxicity. A fume hood keeps most of these vapours within the enclosure and removes them through the exhaust system.

2.3 Lowering fire and explosion risk

Organic labs use many flammable solvents (ether, hexane, petroleum ether, etc.). In a confined, unventilated area, vapours can reach flammable or explosive concentrations and be ignited by:

  • Open flames
  • Hot surfaces
  • Electrical sparks

A properly working fume hood:

  • Dilutes and removes solvent vapours quickly
  • Helps keep vapour concentrations below flammable limits
  • Provides a partial physical barrier (sash glass) that can help deflect minor splashes or small incidents
    (Although it is not a true blast shield.)

2.4 Preventing contamination of the lab environment

Without a hood, volatile and odorous substances can quickly spread through the entire room:

  • Volatile amines
  • Sulfur compounds
  • Acid anhydrides and other strongly smelling reagents

A fume hood keeps most of these confined to the interior and ductwork, reducing persistent smells and contamination on walls, instruments and other people’s experiments.

3. Common fume hood types in organic labs

Fume hoods can be categorised in several ways. For typical organic chemistry teaching and research labs, a few combinations are most relevant.

3.1 Ducted vs ductless

Ducted fume hood (the standard choice)

  • Air from the hood is drawn through ducting by a fan and exhausted to the outside.
  • Handles mixtures of organic vapours, acid/base fumes and other gases (provided duct materials are suitable).
  • Requires building ventilation design and installation; location is relatively fixed.

This is the mainstay of organic chemistry labs.

Ductless (recirculating) fume hood

  • Air passes through filters (often activated carbon) and is then returned to the room.
  • Filter performance depends strongly on the specific chemicals and load.
  • Not suitable as the primary hood for mixed organic synthesis with varied solvents and high vapour loads.
  • Requires strict control and monitoring of filter saturation.

For most organic labs, a ducted chemical fume hood is considered the appropriate standard.

3.2 Constant air volume (CAV) vs variable air volume (VAV)

CAV (Constant Air Volume) fume hood

  • The fan delivers approximately constant total airflow.
  • When you raise the sash (larger opening), the face velocity tends to drop.
  • When you lower the sash, the face velocity rises.

Pros:

  • Simpler design, lower initial cost.

Cons:

  • Face velocity varies with sash position.
  • Energy use is higher, especially with many hoods.

VAV (Variable Air Volume) fume hood

  • A control system adjusts airflow to keep face velocity roughly constant, regardless of sash height (e.g. around 0.5 m/s).

Pros:

  • More stable containment over different sash positions.
  • Better for building energy efficiency.

Cons:

  • More complex and expensive; requires proper maintenance.

In many teaching labs and smaller facilities, CAV hoods are common. In large research buildings or new lab complexes, VAV systems are often used.

3.3 Bench-top vs walk-in

Bench-top fume hood

  • The most common type in organic labs.
  • Mounted on a bench or dedicated base cabinet.
  • Suited for typical glassware setups:
    • Reflux
    • Distillation
    • Vacuum filtration
    • Small reactors

Walk-in fume hood

  • The floor of the hood is close to the room floor.
  • Allows you to roll in large equipment, drums or pilot-scale setups.
  • Usually used for scale-up or specialised operations, not routine small-flask work.

4. When must you work in a fume hood?

As a practical guide, perform work in a fume hood if any of the following apply:

  • You are using or generating significant amounts of volatile organic solvents.
  • You work with toxic, corrosive, strongly irritating or odorous gases or vapours.
  • The reaction may be strongly exothermic or prone to splashing.
  • You handle toxic powders or suspect solids that could become airborne.
  • Your lab manual or supervisor explicitly instructs you to work in the hood.

If you would not want to breathe the vapours for an hour, the hood is probably the right place.

5. Setting up the fume hood before you start

Before bringing chemicals or setting up glassware in the hood, check the following.

5.1 Confirm airflow

  • Make sure the fume hood fan is on.
  • Check any airflow indicator, gauge or alarm (if installed).
  • A simple functional check: hold a small strip of light paper at the front opening and confirm it is drawn steadily into the hood.

If you suspect poor airflow, do not start hazardous work. Inform your instructor or lab supervisor.

5.2 Set the sash to the recommended height

  • Most hoods have a marked safe working height (often around 25–30 cm opening).
  • Work with the sash at or below this mark.
  • Do not automatically raise the sash to full height “for convenience”: this reduces containment.

5.3 Clear clutter and lay out your setup

  • Remove bottles, boxes and equipment that are not needed for the current experiment.
  • Place your apparatus:
    • At least 10–15 cm inside the front edge
    • Away from the direct line of the baffles or slots at the back, without blocking them completely
  • Clamp glassware securely; make sure heating mantles and stirrer plates sit flat and stable.

Remember: the fume hood is not a solvent warehouse. Long-term storage of many bottles inside reduces performance and increases risk.

6. Good practice while working in the hood

6.1 Where you stand and how you move

  • Keep your head and upper body outside the hood.
  • Look through the sash glass and reach through the opening with your arms.
  • Move your hands and arms smoothly; avoid rapid in-and-out motions that can disturb airflow at the face.

Frequent fast movements, opening doors or placing the hood right next to a busy doorway can create turbulence that pulls fumes out towards the room.

6.2 Heating and flames

  • Prefer electric heating: hot plates, heating mantles, oil baths, sand baths.
  • Avoid open flames (Bunsen burners, alcohol lamps) when flammable solvents are present.
  • If a flame must be used (in rare, controlled situations), ensure:
    • Flammable solvent bottles are capped and kept well away.
    • No significant solvent vapours are being generated at the same time.

Never leave heated flammable solvent systems running unattended in the hood.

6.3 Avoiding “storage mode”

  • Do not use the hood as a permanent home for solvent bottles, waste containers or surplus glassware.
  • Long-term storage reduces the free working area and can compromise airflow patterns.
  • Keep only what you need for the ongoing experiment inside; remove the rest.

7. After you finish: shutting down properly

When your experiment is complete:

  1. Allow time for purge
    • Keep the fan running for some minutes (often 5–15 minutes, depending on lab policy) after you stop generating vapours.
    • This helps clear residual contaminants.
  2. Remove or close chemicals and waste
    • Cap reagent bottles and waste containers.
    • Remove them from the hood to their designated storage or waste area if appropriate.
  3. Clean the work surface
    • Wipe up spills with suitable materials and cleaners, following your lab’s procedures.
    • Dispose of contaminated cleanup materials as chemical waste if required.
  4. Lower the sash
    • When not in use, the sash should be closed or lowered as far as your lab policy allows.
    • This improves safety and reduces energy consumption.

8. Quick checklist: using the fume hood wisely

You can adapt this into a clickable checklist later if you like. For now, it works as a simple self-check.

Before you use the fume hood for an experiment, run through this quick checklist:

Before starting

While working

After finishing

9. Safety note

Information on ChemNorth is intended for educational purposes and small-lab guidance. Always follow your institution’s safety rules, equipment manuals and local regulations. If you are unsure whether a procedure should be carried out in a fume hood, ask your instructor, lab supervisor or safety officer before proceeding.

How to Check and Retire Damaged Glassware Safely

Summary
Before you start any experiment, take a moment to inspect your glassware. Any visible crack or chip – anywhere on the piece – is a reason to stop using it. This is especially important for vacuum and thick-walled vessels. Retire damaged items, place broken glass in the correct waste container, and choose appropriate glassware for demanding hot–cold or vacuum work to reduce the risk of cuts and implosions.

1. Why damaged glassware matters

Damaged glassware is more than an aesthetic problem. It adds two kinds of risk to the lab:

  • Cuts and punctures – sharp chips on rims, joints or broken edges can easily cut hands or fingers.
  • Sudden failure during use – cracks can propagate when glass is heated, cooled, clamped or put under vacuum, sometimes leading to breakage or implosion.

The cost of a replacement flask or beaker is always lower than the cost of an injury, lost sample, or damaged equipment. A simple inspection habit before each experiment prevents many avoidable accidents.

2. A simple inspection routine before you use glassware

Do a quick but systematic check before you set up:

2.1 Look along all critical edges

Check every edge that you might touch or that must seal:

  • Rims of beakers, flasks and test tubes
  • Ground-glass joints (inner and outer)
  • Stopcocks and valves
  • Hose barbs, sidearms and adapters

Look for:

  • Chips, missing “bites” of glass
  • Rough or sharp spots
  • White, frosted areas that were not originally ground

2.2 Scan the whole body, not just the rim

Any part of the glass can crack, not only the edge. Inspect:

  • The body of flasks and bottles for straight cracks, curved cracks or “spider-web” patterns
  • The neck and shoulders where the shape changes
  • Side arms and joint transitions, where the wall thickness changes
  • The base for star cracks – radiating lines that start from a point of impact

Rotate the item slowly in good light, or against a dark background, to catch reflections from fine cracks.

2.3 Use your fingers carefully

With clean, dry fingers:

  • Run a fingertip very lightly around rims and joints to feel for nicks
  • Avoid pressing hard or sliding quickly – you are checking, not polishing
  • If a spot feels sharp or irregular, examine it closely in the light

Rule of thumb:

If you can clearly see or feel a crack or chip anywhere on the glass, do not use that item for experiments.

Before you use any piece of glassware, run through this quick checklist:

Check all edges

Check the body and base

Extra care for vacuum and thick-walled glass

3. When a piece must be retired

In a teaching or research lab, it is safer to retire glassware early rather than “see how long it lasts”. Retire an item immediately if you notice:

  • Any visible crack, however short, on the body, neck, joint, side arm or base
  • A chip or missing piece on any rim, ground joint or stopper
  • A star-shaped crack on the bottom or side
  • A joint that no longer seals properly because the glass is visibly worn or chipped
  • Any item that has experienced a strong impact and is now suspected to have hidden damage

For most labs, the safest policy is:

If in doubt, throw it out.

Label suspect glassware clearly (for example, with tape marked “BROKEN / DISCARD”), remove it from the cupboard so it cannot be used by mistake, and move it towards the correct waste route.

4. Special case: vacuum and thick-walled glassware

Vacuum operations and pressure differences place extra stress on glassware.

  • Under reduced pressure, the outside air pushes inwards. Cracks act as stress concentrators, making implosion more likely.
  • Thick-walled glassware such as vacuum flasks, Schlenk lines, cold traps and filter flasks is designed to handle this stress only when it is free of defects.

For vacuum-rated glassware:

  • Inspect before every use – pay special attention to the body, neck and any branches.
  • Never use a piece with visible cracks, chips or star patterns, even if they look small or “stable”.
  • Use guards where available: safety shields, blast screens, or protective cages around large vacuum vessels.
  • Do not rely on tape or plastic film to “hold it together”. These do not restore the strength of the glass.

Once a vacuum vessel has any visible defect, it should be permanently retired from vacuum service. In most labs, the safest approach is to discard it completely rather than downgrade it to non-vacuum use, to avoid confusion later.

Quick question

You are about to set up a vacuum distillation using a thick-walled 100 mL round-bottom flask. When you inspect it, you notice a short, fine crack near the shoulder of the flask that is clearly visible in the light. What should you do?

  1. A. Use the flask anyway but reduce the vacuum level.
  2. B. Wrap tape or film around the crack and then use the flask.
  3. C. Retire the flask from service and choose an undamaged vacuum flask.
Show suggested answer

Retire the flask from service and choose an undamaged vacuum flask.
Any visible crack in a vacuum-rated vessel is a serious hazard, because stress is concentrated at the defect and can lead to implosion under reduced pressure. Tape or lower vacuum do not restore the original strength of the glass. The safest option is to remove the damaged flask from use and replace it with an intact, properly rated vacuum flask.

5. How to deal with damaged or broken glass

5.1 Damaged but still in one piece

If a piece is intact but damaged:

  1. Stop using it immediately.
  2. Mark it clearly (for example, with tape or a label saying “BROKEN / DISCARD”).
  3. Place it in the designated area for broken glass, or in a container waiting to be emptied into the glass waste bin.
  4. Inform the lab supervisor if local rules require it.

Do not put damaged glass back in the cupboard “to think about later”. It will eventually be picked up by someone who assumes it is fine.

5.2 Completely broken glass

When glass breaks:

  • Warn people nearby so they do not step on fragments.
  • Wear appropriate gloves and closed shoes.
  • Use tongs, forceps, a brush and pan, or a piece of stiff cardboard to collect fragments. Avoid picking up shards with bare hands.
  • Place all pieces into the designated glass-waste container – not into normal trash bags, where they can injure cleaning staff.
  • If glass is contaminated with chemicals, follow your lab’s procedure for chemical-contaminated glass waste (for example, labelled glass waste containers or special bags).

A rigid, puncture-resistant glass waste container is standard in most labs. It protects everyone who handles waste downstream.

6. Choosing glassware for demanding heating and cooling

Thermal shock resistance depends mainly on the type of glass. For most high-quality labware, this means borosilicate 3.3 glass, which tolerates heating and cooling better than ordinary soda-lime glass.

Within the same glass type, the way glassware is made also matters:

  • Blown or flame-worked glassware tends to have more uniform wall thickness and smoother transitions between sections. This helps distribute thermal stress more evenly.
  • When such pieces are properly annealed after forming, internal residual stress is reduced, so they are less likely to crack under rapid heating or cooling.

For applications that combine high temperatures with repeated hot–cold cycling – such as reflux, distillation, or heating and then quenching – it is often safer to:

  • Use well-annealed, blown borosilicate glassware explicitly specified for those conditions,
  • Avoid heavy moulded pieces with sharp changes in thickness where thermal stress can concentrate.

This does not mean moulded glassware is unsafe; it is perfectly adequate for many routine tasks. The key is to match the design and specification of the glassware to the temperature and thermal-shock conditions of your experiment, and to continue inspecting pieces regularly over their lifetime.

Why You Must Never Eat, Drink or Mouth-Pipet in the Lab

Summary
In a lab, anything that reaches your mouth can carry invisible chemical or biological contamination. Eating and drinking in the lab, or pipetting by mouth, turns that invisible risk into a direct exposure. Modern lab safety rules ban food and drink in experimental areas, forbid mouth pipetting, and require thorough handwashing before you leave the lab or touch food. Second-hand and returned glassware also demand extra care: treat them as potentially contaminated until they are properly cleaned.

1. How chemicals reach your mouth in a lab

When people think about chemical exposure, they often focus on spills or fumes. But one of the most straightforward and dangerous routes is ingestion – chemicals entering through your mouth and digestive tract.

In a lab, this can happen in several ways:

  • Tasting or “checking by mouth”
    Historically, some chemists really did taste small amounts of substances to identify them. Today, this is recognised as unnecessary and unsafe.
  • Mouth pipetting
    Drawing liquids into a pipette by sucking with your mouth can send the liquid, aerosols or vapour directly into your mouth or throat if you misjudge the volume or lose control.
  • Contaminated hands touching food, drinks or your face
    You handle glassware, reagents, second-hand or returned items, and then:
    • eat a snack,
    • drink water or coffee,
    • touch your lips or wipe your mouth
      without washing your hands thoroughly.
  • Food and drink stored or opened in the lab
    Even if you never “taste chemicals”, food and drink left on lab benches can be contaminated by splashes, vapour, dust or dirty gloves.

The common pattern is simple: any object that lives in the lab environment can carry residues you cannot see.

2. Why labs ban food and drink completely

Most lab safety manuals include a strict rule: no eating, no drinking, no food storage in laboratories. This is not about being strict or unfriendly; it is about breaking the most direct path for ingestion.

2.1 Invisible residues are everywhere

In a lab, many surfaces can carry small amounts of chemicals:

  • The benchtop where you work
  • Glassware, even if it “looks clean”
  • Pipettes, clamps, racks and instruments
  • Your notebook, pens and keyboard if you touch them with contaminated gloves

These residues can be:

  • Organic solvents
  • Corrosive or irritant reagents
  • Heavy metals or other toxic compounds
  • Biological materials in some labs

You cannot see or smell most of these in the small amounts that matter for chronic exposure.

2.2 A real-world lesson: eating after handling glassware

In one glass factory, a worker was asked to check returned glassware that a customer had sent back. He handled the glass instruments with bare hands to inspect them, without knowing exactly what they had been used for or what residues might be present.

After the inspection, he did not wash his hands. He then picked up food and ate. Shortly afterwards, he developed signs of poisoning and later died.

We do not need the exact chemical identity to understand the chain of events:

  1. Returned or second-hand glassware may have unknown residues on the surface.
  2. Handling them with bare hands transfers residue to the skin.
  3. Eating without washing hands transfers residue from skin to mouth.

This kind of tragedy is not dramatic or exotic. It is a series of small, very ordinary decisions:

  • “I’m just touching glass, not chemicals.”
  • “I’ll eat first, wash my hands later.”

The rule “no eating or drinking in the lab, always wash hands before food” exists to break this chain.

2.3 Practical rule

Because of these risks, a safe lab policy is:

  • No food, drink, chewing gum or smoking in experimental areas.
  • No storage of food or drink in lab fridges, freezers or cabinets.
  • Eat and drink only outside the lab, after washing your hands thoroughly with soap and water.

3. Why mouth pipetting is completely banned

Mouth pipetting once was common in chemistry and biology labs. Today, it is recognised as a completely unacceptable practice.

3.1 What goes wrong when you pipet by mouth

When you suck on a pipette:

  • The liquid is very close to your mouth.
  • If you misjudge the suction or the liquid “jumps”, it can enter your mouth or throat.
  • Even if you spit it out quickly, your lips and mucous membranes have already been exposed.

In some cases, droplets or aerosols may enter your airway before you even notice.

3.2 The types of risk

The liquid you are pipetting might be:

  • A toxic organic solvent
  • A corrosive acid or base
  • A solution containing heavy metals
  • A biological sample carrying infectious agents

Historically, some laboratory-acquired infections and poisonings have been linked to mouth pipetting. This is why modern safety standards and institutional rules are unanimous: mouth pipetting is forbidden in professional labs, teaching labs and serious small labs.

3.3 Safer alternatives

Modern labs have simple tools that make mouth pipetting unnecessary:

  • Rubber pipette bulbs
  • Manual pipette controllers
  • Adjustable volume micropipettes with disposable tips

These devices:

  • Keep liquids away from your mouth
  • Give you much better control over volume
  • Are inexpensive compared to the cost of an incident

A good habit is:

If you ever see mouth pipetting in a lab, treat it as an urgent safety issue, not a matter of “style” or “speed”.

4. Second-hand and returned glassware: treat as “unknown”

Second-hand lab glassware and customer returns can be valuable resources, but they also carry invisible history.

You often do not know:

  • Exactly what was in them last time
  • Whether they were used correctly or misused as temporary containers
  • Whether residues have dried on surfaces, joints or threads

4.1 Handling second-hand or returned glassware

When you unpack or inspect second-hand or returned glass:

  • Assume that it may carry unknown contamination.
  • Whenever possible, wear appropriate gloves.
  • Avoid touching your face, phone or personal items during inspection.
  • After handling, wash your hands thoroughly before eating, drinking or leaving for a break.

This applies both in a lab that buys second-hand glassware and in a glassware factory or warehouse that handles returns.

4.2 Cleaning before use in experiments

Before using second-hand or returned glassware in experiments:

  • Put it through a thorough cleaning cycle:
    • Suitable detergent wash
    • Multiple rinses with tap water and then deionised/distilled water
    • Special cleaning procedures as required by your lab
  • If the previous use is unclear and the potential risk is high, your lab may decide to discard the item rather than reuse it.

A simple principle is:

Treat any glassware of unknown history as a potential chemical container until it has been properly cleaned.

5. Building safer everyday habits

Rules only help if they translate into daily habits. The key behaviours for reducing ingestion risk are simple but powerful:

5.1 For eating and drinking

  • Keep all food and drink out of the lab.
  • Never store food or beverages in lab refrigerators or freezers.
  • Before eating, drinking or smoking:
    • Leave the lab
    • Remove gloves and other contaminated PPE
    • Wash your hands thoroughly with soap and water

5.2 For pipetting and liquid handling

  • Never pipet by mouth, even “just water” – habits transfer across tasks.
  • Use pipette bulbs, manual controllers or micropipettes.
  • Store pipetting devices and tips in a clean area, away from direct contamination.
  • Train new lab members explicitly: “We do not mouth pipet, ever.”

5.3 For second-hand and returned glassware

  • Treat unknown glassware as contaminated until cleaned.
  • Wear gloves when inspecting or sorting.
  • Wash your hands after handling, before any break or meal.
  • Do not assume that “it’s just glass” and therefore safe.

Small actions repeated every day—no food in the lab, no mouth pipetting, washing hands—create a long-term barrier against serious incidents.

6.Checklist: before you eat, drink or leave the lab

Before you eat, drink or leave the lab, run through this quick checklist:

Have I been in contact with lab surfaces or materials?

Am I about to eat or drink?

For pipetting

7. Mini quiz: what is the real problem?

Mini quiz

Which of the following behaviours is clearly unsafe because of ingestion risk?



Show suggested answer

Inspecting returned lab glassware with bare hands in the lab and then eating a snack without washing your hands.
Returned or second-hand glassware may carry unknown chemical residues on their surfaces. Handling them with bare hands and then eating without washing transfers any contamination directly to your mouth. New glassware opened in a clean office after handwashing, and properly gloved work with sealed bottles followed by glove removal, are much lower-risk behaviours when done correctly.

8. Safety note

Information on ChemNorth is for educational purposes and for small-lab guidance. Always follow your institution’s safety rules and local regulations. If you are unsure whether a behaviour is safe, ask your instructor, lab supervisor or safety officer before proceeding.

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.