{"id":52040,"date":"2025-09-13T04:40:30","date_gmt":"2025-09-12T19:40:30","guid":{"rendered":"https:\/\/phys-edu.net\/wp\/?p=52040"},"modified":"2026-05-15T05:04:48","modified_gmt":"2026-05-14T20:04:48","slug":"the-perilous-promise-of-iron-and-sulfur-13-crucial-safety-steps-for-a-middle-school-science-experiment","status":"publish","type":"post","link":"https:\/\/phys-edu.net\/wp\/?p=52040&lang=en","title":{"rendered":"Warning: Safety First! 13 Essential Keys to Mastering the “Iron & Sulfur” Experiment (Preventing Hydrogen Sulfide Risk)"},"content":{"rendered":"

I\u2019m Kuwako Ken, the Science Trainer. Every day is an experiment.<\/strong><\/p>\n

\u3010This article is also available as a radio episode!<\/a>\u3011<\/p>\n

If you\u2019ve ever visited a hot spring town, you probably know that strange smell drifting through the air. Kind of like rotten eggs\u2026 yet somehow oddly comforting. That smell comes from hydrogen sulfide<\/b>. Since I grew up in Gunma Prefecture, famous for its hot springs, the scent actually feels nostalgic to me.<\/p>\n

One of the classic middle school science experiments in Japan involves mixing iron and sulfur and heating them together. It\u2019s not only a beautiful demonstration of chemical reactions, but also a rare chance for students to experience chemistry with all five senses. They see the glowing reaction, smell the gas produced, and truly feel that matter is changing into something completely new.<\/p>\n

\"\"<\/p>\n

Unfortunately, in recent years, accidents related to this experiment have been reported across Japan. Just searching \u201chydrogen sulfide accident\u201d brings up alarming stories. Sometimes a student ignores instructions and pours in far too much hydrochloric acid. That single mistake can escalate into a major safety issue, and in some cases even puts the future of hands-on science classes at risk.<\/p>\n

\uff1cExamples of reported accidents\uff1e
\n\u30fbPossible hydrogen sulfide exposure at a junior high school in Edogawa, Tokyo \u2014 five students became ill<\/a>\uff08Asahi Shimbun\uff09\uff082026\/05\/15\uff09
\n\u30fbIs the hydrogen sulfide experiment still necessary? Repeated emergency transports raise concerns<\/a>\uff08Mainichi Shimbun\uff09\uff082025\/6\/19\uff09<\/p>\n

https:\/\/youtu.be\/QwMtCDEYjjs?si=wWNO55szEuiigQEE<\/p>\n

Even so, I still believe this experiment is worth doing.<\/p>\n

The moment iron and sulfur react and begin glowing red is unforgettable. Students remember it for years.<\/p>\n

\"\"<\/p>\n

And the experience of learning \u201cthis smell means danger\u201d could someday protect their lives at a hot spring, construction site, or other real-world setting. That\u2019s exactly why the experiment must be carried out carefully, correctly, and safely<\/b>.<\/p>\n

This experiment is meaningful and educational for both students and science teachers. But if safety cannot be guaranteed, it should not be done.<\/strong><\/span><\/p>\n

In this article, I\u2019ll share the 13 safety checkpoints<\/b> that I review every year before teaching this lesson. At the end, I\u2019ve also included the actual safety instruction slides<\/a> I use in class. Feel free to use them however you like.<\/p>\n

Before every lesson, I personally run the experiment multiple times in advance. Thankfully, I\u2019ve avoided major accidents so far, but I always approach this experiment with a healthy sense of caution.<\/p>\n

\u203b I often receive messages asking, \u201cCan I use these photos or slides in my own classes?\u201d Absolutely. Everything posted here is free to use.<\/b> I hope it helps make science lessons safer, more effective, and more exciting.<\/p>\n

Experiment Procedure<\/h2>\n

Advance preparation and ventilation \uff1cSafety starts before class even begins\uff1e<\/h3>\n

Before the lesson, let the school nurse and homeroom teacher know that you\u2019ll be conducting this experiment. If anything unexpected happens, quick coordination becomes much easier. Students should also be reminded ahead of time to bring lab coats and safety goggles.<\/p>\n

And don\u2019t forget the ventilation fan.<\/p>\n

On experiment day, teachers are usually overwhelmed with setup and student management. You remember to open the windows\u2026 but forget to turn on the fan. It happens surprisingly often. That\u2019s why it\u2019s best to make turning on the ventilation system part of your pre-class routine.<\/p>\n

Checkpoint 0: Inform the school nurse and homeroom teacher beforehand.<\/b><\/span><\/p>\n

Checkpoint 1: Turn on the ventilation fan before class starts so you won\u2019t forget later.<\/b><\/span><\/p>\n

\"\"<\/p>\n

The ventilation switch in our science room<\/p>\n

Step 1: Thoroughly mix iron filings and sulfur\uff087.0 g iron, 4.0 g sulfur\uff09<\/h3>\n

To finish the experiment within a standard 50-minute class, it\u2019s best for the teacher to prepare the measurements ahead of time.<\/p>\n

If there\u2019s too much sulfur, sulfur vapor is more likely to form, so accurate measurement directly affects safety.<\/p>\n

The particle size of the iron filings also matters. Coarse 60-mesh iron sometimes reacts poorly. Use 100 mesh or finer<\/b>. In this experiment, I used 300-mesh iron powder.<\/p>\n

Why does this matter? Smaller particles mean more surface area where iron and sulfur can touch, making the reaction smoother and more stable.<\/p>\n

\"\"<\/p>\n

Checkpoint 2: Use iron powder that is at least 100 mesh!<\/b><\/span><\/p>\n

Rakuten: 300-mesh iron powder<\/a><\/p>\n

\"\"<\/p>\n

Place the iron and sulfur in a mortar and mix thoroughly.<\/p>\n

It\u2019s convenient to keep separate mortars for iron sulfide experiments<\/b> and copper oxide experiments<\/b>. That way, you can reuse them for the next class without washing in between.<\/p>\n

\"\"<\/p>\n

Keep mixing until the entire powder turns gray. If yellow sulfur clumps remain, the reaction becomes uneven, and excess sulfur may vaporize.<\/p>\n

A completely gray mixture is your visual cue that it\u2019s ready.<\/p>\n

Checkpoint 3: Mix thoroughly. Poor mixing can produce sulfur vapor.<\/b><\/span><\/p>\n

Reference: Sulfur melts at 112\u00b0C and boils at 446\u00b0C. A gas burner flame reaches around 1500\u00b0C.<\/b><\/p>\n

\"\"<\/p>\n

This is an example of poor mixing.<\/b> Yellow sulfur clumps are still visible. Keep mixing until everything becomes gray.<\/strong><\/span><\/p>\n

Step 2: Make two aluminum foil containers and fill them with the mixture<\/h3>\n

\"\"<\/p>\n

Prepare aluminum foil pieces about 5 cm \u00d7 10 cm ahead of time.<\/p>\n

Tape together two AAA batteries to use as a mold. Wrap the foil tightly around them while pressing firmly against the desk. Seal one end, remove the batteries, and you\u2019ve got a sturdy aluminum container. Make two of them.<\/p>\n

\"\"<\/p>\n

Roll it up gently by hand.<\/p>\n

\"\"<\/p>\n

Transfer the mixed sample onto weighing paper, then use a funnel to pour it into the aluminum tube.<\/p>\n

After filling, lightly tap the tube against the desk to remove trapped air and improve contact between the particles.<\/p>\n

Warn students not to tap too hard, or the foil may tear.<\/b><\/p>\n

Also, funnels can simply be reused for the next class without washing.<\/b><\/p>\n

\"\" \"\"<\/p>\n

Step 3: Heat the sample in a test tube \uff1cThe glowing red reaction \u2014 the highlight of the experiment!\uff1e<\/h3>\n

Label the two samples \u201ca\u201d and \u201cb.\u201d Leave sample b untouched as a control.<\/p>\n

Place sample a into a test tube, plug the opening with cotton<\/b>, and heat the upper part of the aluminum container<\/b>.<\/p>\n

There\u2019s an important reason for heating from the top.<\/p>\n

If you heat the bottom directly, the combined heat from the burner and the chemical reaction can crack the test tube, causing the contents to fall out suddenly.<\/p>\n

Starting the reaction from the top keeps the tube cleaner and allowed me to reuse the same test tubes across four classes.<\/p>\n

\"\"<\/p>\n

Checkpoint 4: Plug the tube with cotton to reduce the release of toxic sulfur vapor.<\/b><\/span><\/p>\n

\"\"<\/p>\n

Checkpoint 5: Heat the top of the foil container, not the bottom.<\/b><\/span><\/p>\n

\"\"<\/p>\n

Checkpoint 6: Attach the test tube holder near the top of the tube. Never hold the squeezing part while heating, or it may accidentally open.<\/b><\/span><\/p>\n