3 Ways to Make Sulfur Dioxide Gas

Summary

This video demonstrates three methods to generate sulfur dioxide gas, often used in chemistry for making sulfuric acid and as a reductant in metal refining. The methods include burning sulfur, decomposing sulfuric acid with sulfur, and acidifying sodium metabisulfite. Each approach has varying cost, complexity, and safety considerations. The video explains setups for safely capturing and using sulfur dioxide, with tips for different scales of reaction. While the metabisulfite method is the most expensive, it offers instant, convenient gas production. The video concludes with a thank you to Patreon supporters.

Takeaways

• ⚠️ Warning: This experiment generates toxic sulfur dioxide gas, requiring work outside or in a fume hood and the use of gloves when handling hydrochloric and sulfuric acids.
• 🔬 Sulfur dioxide is generally unwanted due to its toxicity, contribution to acid rain, and damage to catalytic converters, but is useful in making sulfuric acid and as a gaseous reductant.
• 🔥 The cheapest method to produce sulfur dioxide is by burning sulfur, which requires building a gas capture setup using a metal funnel, copper tubing, and a vacuum pump.
• 🏞️ Elemental sulfur is easy to obtain for gardening uses and pest control.
• 📡 The gas capture setup cools the hot sulfur dioxide and directs it into a reaction flask using a vacuum pump.
• 🔧 The vacuum pump must be placed outside or in a fume hood to avoid exposure to sulfur dioxide.
• 🧪 The sulfuric acid decomposition method involves reacting concentrated sulfuric acid with elemental sulfur in a distillation setup, but it is slow, risky, and not efficient for making sulfur dioxide.
• ⚗️ The sodium metabisulfite acidification method uses water, sodium metabisulfite, and hydrochloric acid to generate sulfur dioxide instantly, making it convenient but more expensive.
• 💰 While the metabisulfite method is costly, it is straightforward and doesn't require complex equipment or heating.
• 📽️ The video thanks supporters on Patreon for enabling the production of science videos and encourages viewers to support the channel.

Q & A

What are the three methods discussed for generating sulfur dioxide (SO2)?

The three methods discussed for generating sulfur dioxide are burning sulfur, sulfuric acid decomposition, and sodium metabisulfite acidification.

Why is sulfur dioxide considered an unwanted substance in many cases?

Sulfur dioxide is considered unwanted because it's toxic, contributes to acid rain, damages catalytic converters in cars, and is generally harmful to the environment and health.

What is the cheapest method of generating sulfur dioxide, and what are the main steps involved?

The cheapest method is burning sulfur. The steps involve packing sulfur into a candle form, igniting it, and using a gas capture setup to cool and direct the sulfur dioxide for use in reactions.

What is the purpose of the copper tubing in the sulfur burning method?

The copper tubing is used to cool the hot sulfur dioxide gas that is produced during the burning of sulfur before directing it to the reaction flask.

What is the main safety concern when using the sulfuric acid decomposition method?

The main safety concern is dealing with boiling hot sulfuric acid, which can be dangerous, especially for amateur chemists, due to the risk of burns and exposure to toxic fumes.

Why is the sulfuric acid decomposition method considered inefficient for generating sulfur dioxide to make sulfuric acid?

This method is inefficient because it consumes both sulfuric acid and sulfur, making it a less cost-effective option if the goal is to produce sulfur dioxide for further sulfuric acid production.

What is a potential problem with the sulfuric acid decomposition method related to sulfur vaporization?

At high temperatures, small amounts of sulfur can vaporize and condense onto the inner walls of the distillation apparatus, potentially clogging it over time.

What makes the sodium metabisulfite acidification method more convenient than the other two methods?

The sodium metabisulfite acidification method is more convenient because it produces sulfur dioxide instantly on demand, without the need for heating or complex setups like coolers or vacuum pumps.

What are the main disadvantages of the sodium metabisulfite acidification method?

The main disadvantage is its cost, as it requires relatively expensive reagents, specifically sodium metabisulfite and hydrochloric acid.

Why might some amateur chemists prefer using sodium metabisulfite over sulfuric acid?

Some amateurs might prefer sodium metabisulfite because it is readily available online, often easier to obtain than sulfuric acid, and involves a simpler and safer setup for generating sulfur dioxide.

Outlines

00:00

⚠️ Handling Sulfur Dioxide: Introduction and Method 1 - Burning Sulfur

This paragraph serves as a warning about the toxicity of sulfur dioxide gas and the hazards of using hydrochloric and sulfuric acids in the experiment. The video focuses on demonstrating three methods of producing sulfur dioxide, often used in amateur chemistry for making sulfuric acid and as a reductant. The first method involves burning sulfur, the cheapest and simplest technique, though it requires setting up a gas capture system to direct the produced sulfur dioxide. The setup includes a metal funnel, copper tubing to cool the gas, and a vacuum apparatus to pull the gas into a reaction flask. The paragraph also warns about the dangers of sulfur dioxide exposure from improper setup and emphasizes the importance of using proper ventilation. This method is useful for large-scale sulfur dioxide generation, but can be labor-intensive.

05:05

⚗️ Method 2 - Sulfuric Acid Decomposition for Sulfur Dioxide

This paragraph covers the second method: generating sulfur dioxide by heating concentrated sulfuric acid with elemental sulfur. A sealed distillation setup is used to collect and cool the gas, though the process risks clogging the apparatus due to sulfur vapor condensing inside. This reaction is a comproportionation, meaning sulfur and sulfuric acid react to produce sulfur dioxide and water. While this method yields relatively pure sulfur dioxide, it's considered inefficient and risky for amateurs due to the hazards of handling boiling sulfuric acid. The main advantage is that the gas is produced without the presence of air, making it useful for certain reactions.

💰 Method 3 - Sodium Metabisulfite Acidification for Convenient Sulfur Dioxide Production

The final method described uses sodium metabisulfite and hydrochloric acid to instantly generate sulfur dioxide. This method is more expensive but highly convenient, as it requires no heating or complex equipment, and the sulfur dioxide is produced on demand. The reaction between the acid and metabisulfite produces sulfur dioxide and salt, with the generation rate controlled by the drip rate of hydrochloric acid. The method is highly accessible, with sodium metabisulfite being readily available as a disinfectant and preservative. It's favored for its simplicity and ease of use, despite the higher reagent cost.

Keywords

💡Sulfur Dioxide

Sulfur dioxide is a toxic gas generated in the video through three methods: burning sulfur, sulfuric acid decomposition, and sodium metabisulfite acidification. It is an unwanted byproduct in many cases due to its harmful effects, such as causing acid rain, but in amateur chemistry, it is often used to create sulfuric acid or as a gaseous reductant. The video focuses on its production methods and usage in chemical reactions.

💡Burning Sulfur

This is the first and most economical method to produce sulfur dioxide in the video. The process involves burning elemental sulfur, which is easily available for gardening and pest control. The sulfur combusts with oxygen to produce sulfur dioxide, but the video explains the need for a gas capture setup to utilize the gas effectively in chemical reactions.

💡Sulfuric Acid Decomposition

Sulfuric acid decomposition is the second method shown in the video to produce sulfur dioxide. In this method, elemental sulfur is reacted with concentrated sulfuric acid in a distillation setup. While this produces a relatively pure form of sulfur dioxide without excess air, it is considered inefficient and potentially dangerous due to the boiling sulfuric acid and vaporized sulfur.

💡Sodium Metabisulfite

Sodium metabisulfite is the chemical used in the third and most convenient method to generate sulfur dioxide. When reacted with hydrochloric acid, it instantly produces sulfur dioxide and salt. This method is praised for its ease and quick results, though it is more expensive than the others. Sodium metabisulfite is also widely available for food preservation and disinfection.

💡Aspirator Vacuum Pump

An aspirator vacuum pump is recommended in the video for pulling sulfur dioxide gas through the reaction setup during the burning sulfur method. This pump creates a vacuum that helps transport the gas into the reaction flask. However, the video warns about potential contamination of the pump with sulfur dioxide, which could cause harmful exposure.

💡Comproportionation

Comproportionation is the chemical reaction highlighted in the sulfuric acid decomposition method, where sulfur and sulfuric acid react to produce sulfur dioxide and water. It is the reverse of disproportionation reactions, where a single substance is both oxidized and reduced. The video notes that this process is less efficient for sulfur dioxide generation compared to burning sulfur.

💡Vacuum Adapter

The vacuum adapter is a critical component in the gas capture setup used in the burning sulfur method. It helps channel the sulfur dioxide into the reaction by pulling the gas under vacuum pressure. The video demonstrates how the vacuum adapter functions, emphasizing its importance in making the sulfur dioxide usable without a sealed combustion chamber.

💡Hydrochloric Acid

Hydrochloric acid is used in the sodium metabisulfite acidification method to generate sulfur dioxide. By reacting with sodium metabisulfite, the hydrochloric acid triggers a chemical reaction that produces sulfur dioxide gas. This method is highly efficient and convenient, making it popular among amateur chemists despite the higher cost.

💡Distillation Setup

A distillation setup is used in the sulfuric acid decomposition method to cool and collect the sulfur dioxide gas. The setup includes components like a flask, condenser, and gas line. The video warns that improper temperature control can lead to vaporized sulfur clogging the apparatus, making this method more complex and less appealing.

💡Gas Capture Setup

The gas capture setup is required for the burning sulfur method to collect and utilize sulfur dioxide. It consists of a funnel, copper tubing to cool the gas, and plastic tubing connected to a reaction flask. The video explains the importance of this setup in controlling the flow and temperature of the sulfur dioxide for safe use in chemical reactions.

Highlights

Warning: This experiment generates toxic sulfur dioxide gas. Work outside or in a fume hood.

Sulfur dioxide is toxic, contributes to acid rain, and can damage catalytic converters in cars.

Sulfur dioxide is used as a precursor for sulfuric acid production and as a gaseous reductant.

Burning sulfur is the cheapest method to produce sulfur dioxide but requires a gas capture setup.

A crude sulfur candle can be made by packing sulfur into a toilet paper roll and setting it on fire.

Copper tubing is used to cool sulfur dioxide gas, with a vacuum pulling it into the reaction flask.

Vacuum pumps must be placed outside or in a fume hood to avoid exposure to toxic gases.

The sulfuric acid decomposition method produces sulfur dioxide through a comproportionation reaction with sulfur.

This method is less efficient than burning sulfur and involves the risk of handling boiling sulfuric acid.

For cost-sensitive work, such as metal refining, the sulfuric acid decomposition method may be preferred.

The sodium metabisulfite acidification method is the most expensive but also the most convenient for producing sulfur dioxide.

The sodium metabisulfite method generates sulfur dioxide instantly and at room temperature without the need for a vacuum pump or heating.

Sodium metabisulfite is widely available as a disinfectant and preservative, making it accessible for amateur chemists.

The drip rate of hydrochloric acid controls the sulfur dioxide generation rate in the sodium metabisulfite method.

This video compiles three methods to make sulfur dioxide, demonstrating options based on cost, convenience, and purity requirements.

Transcripts

Warning: This experiment generates toxic sulfur dioxide gas.

Work outside or in a fume hood.

This experiment also uses hydrochloric and sulfuric acids.

Wear gloves when handling them.

Greetings fellow nerds.

In this video we're going to show three ways to make sulfur dioxide.

By itself, sulfur dioxide is rather unwanted since it's toxic, makes acid rain, damages the catalytic converters in cars and is overall not a pleasant substance.

It's mostly used by the amateur chemist as a precursor to making sulfuric acid and occasionally as a gaseous reductant.

It finds some use among metal refiners as a cleaner way to reduce or drop precious metals than sodium metabisulfite.

I've demonstrated multiple ways to make it over the years as part of other videos

but I thought I would assemble them into a compilation video so the processes are easier to search for on youtube.

So let's get started.

The first and by far the cheapest method is to simply burn sulfur.

I have it packed into a toilet paper roll to make a crude sulfur candle and all we have to do is set it on fire.

Granted, it does need to be molten for the flame to be self sustaining but that isn't too hard to do.

Elemental sulfur is actually rather easy to get for gardening uses and pest control.

The flame is very dim, but it is there and can be seen if you turn out the lights.

The reaction is very simple, it's just combusting with oxygen to make sulfur dioxide.

Anyway, burning sulfur is cheap, but by itself it's useless since you still need to direct the sulfur dioxide produced.

So we need to build a gas capture setup.

We start with a metal funnel over the burning sulfur and to that we connect a long coil of copper tubing using some aluminum duct tape.

I know this looks pretty stupid but the copper tubing is to cool the hot sulfur dioxide gas that just came off the candle.

You actually don’t need this much metal tubing, I found the gas sufficiently cool after just 2 meters of tubing, or about 6 feet.

I was just too lazy to cut my tubing down.

Anyway, it's then connected using easier to bend plastic tubing to the reaction flask where we have whatever chemicals we want to react with.

Now the gas won't push itself into the apparatus, so instead we pull it using a vacuum by connecting the reaction flask to a vacuum adapter.

Here's a closeup of the adapter, as we pull a vacuum through the adapter gas is pulled through the top of the adapter and into our reaction through that inner tube.

The same tube that connects to our cooling apparatus.

This allows us to use sulfur dioxide without having to build a sealed combustion chamber.

We've already shown how to make a fairly cheap aspirator vacuum pump in a previous video for use with this setup.

If your reaction is safe toward the metals of the aspirator pump, you can also use the aspiration pump itself as the reaction vessel and simply add your chemicals to the pump water.

But I personally don't recommend this as contaminating your aspirator pump apparatus with chemicals is messy and more headache than its worth during cleanup.

A special note if you're using this setup, you'll need to put your vacuum pump outside or in a fumehood as a small amount of sulfur dioxide will get pulled into the pump and exit out the exhaust.

So do not have it in the main workspace of your lab or you'll get gassed with sulfur dioxide

Anyway, that's how we make and utilize sulfur dioxide from burning sulfur.

It's the cheapest source of sulfur dioxide but it is somewhat involved since we have to make this gas capture setup to use it.

But if you're using very large amounts of sulfur dioxide for large scale reactions, this might be the best and most economical method for you.

The next method i want to demonstrate is the sulfuric acid decomposition method.

In this method we get concentrated sulfuric acid and add elemental sulfur to it.

Then we build around it a sealed distillation setup with the gas line serving as our output of sulfur dioxide.

This line is lead into our reaction.

To use the generator we turn on the heating high enough to gently boil the sulfuric acid but not hard enough to distill it.

At this temperature the sulfur and sulfuric acid react to produce sulfur dioxide and water.

This reaction is actually called comproportionation, which is the exact opposite of disproportionation.

As you can see it consumes sulfuric acid and sulfur so if your objective is to make sulfur dioxide to in turn make sulfuric acid, this reaction is probably not the most efficient.

The reason why we built the whole distillation apparatus around it is to cool the hot sulfur dioxide as it comes out.

Additionally the reaction will generate small amounts of water that boil out.

A big problem though is that at these temperatures small amounts of sulfur will vaporize and condense onto the inner walls of the distillation apparatus clogging it up over time.

You can minimize this by using a large flask and trying to adjust the temperature just right that it's just enough to boil but low enough to keep most of the sulfur from vaporizing into the condenser.

Overall i find this method more trouble than it's worth.

It's rather slow and concentrated sulfuric acid is too valuable for the amateur to waste on making sulfur dioxide when the burning method can be used.

On a safety note, dealing with boiling hot sulfuric acid has its own dangers that most amateurs just shouldn't risk.

But this method does have the advantage that the sulfur dioxide is rather pure and doesn't have large amounts of air with it.

For some reactions, having air may be a problem.

In terms of cost, this is cheaper than the metabisulfite method i'll show later and for cost sensitive work like precious metal refining this might be important.

Additionally, not needing a vacuum pump may be desirable for some.

You just need a hotplate capable of boiling sulfuric acid, it doesn't need to stir.

So that leaves the final and most expensive method, sodium metabisulfite acidification.

To make the generator we start with some water and for this example we'll start with 100mL.

To this we add 95g of sodium metabisulfite.

On top of this we setup a gas adapter and a pressure equalized dripping funnel.

To the funnel we add 120mL of 10 Molar or 30% hydrochloric acid and seal it.

You can multiply the ratio to whatever you need for your application.

To use the generator we just open the valve and drip in the hydrochloric acid.

The acid reacts with the sodium metabisulfite to generate sulfur dioxide and salt.

We can then lead the sulfur dioxide into whatever reaction we want.

And the drip rate loosely controls the generation rate.

This method is rather expensive in terms of reagents but it's tremendously convenient since the sulfur dioxide is produced instantly on demand

and you don't have to wait for the generator to heat up like the sulfuric acid decomposition method.

The setup is very straightforward and the gas is already room temperature and reasonably pure.

We don't need unwieldy coolers, high temperatures, or complicated vacuum pumps.

Sodium metabisulfite might seem exotic, but its readily available online and there isn't much restriction on it.

For some amateurs its easier to obtain than sulfuric acid.

It's used a lot as a disinfectant and preservative in food preservation and storage.

You've seen me use this method pretty much exclusively for all the times I've needed sulfur dioxide and while it is expensive the convenience is worth it for most cases.

So that was three ways to make sulfur dioxide gas.

Thanks for watching.

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