How to Make Iodine From Sulfuric Acid and an Alkali Metal Iodide




Introduction: How to Make Iodine From Sulfuric Acid and an Alkali Metal Iodide

About: NurdRage is a dedicate group of science nerds trying to further amateur science with direct how-to instructions in video format. We saw what was already online and we thought "we could do better".....

How to make elemental iodine from sulfuric acid and sodium or potassium iodide.

Warning: Reaction must be done outside or in a fumehood due to production of toxic gases including hydrogen sulfide. Concentrated sulfuric acid is extremely corrosive and dangerous and should be handled in glass containers at all times. Always wear gloves when working with it and thoroughly wash any spills with water. Wear eye protection at all times.

The Iodine vapor that is formed throughout most steps of this instructable is toxic and will also stain EVERYTHING it comes in contact with. You can see from the video that the work-area became an absolute mess. So do not do this indoors.

First, get your sodium or potassium iodide and completely dissolve it in a minimum of water. Then place it into an ice bath to keep it cold.

Second, add concentrated sulfuric acid directly to the solution and constantly stir. As you add it will produce iodine. At this point, it will start producing toxic gases including hydrogen iodide, sulfur dioxide, hydrogen sulfide and vaporized sulfuric acid. You have to perform this reaction outside or in a fumehood.

At first the mixture will become pasty and eventually liquefy.

Once it's liquefied, pour it directly into cold water (the ice bath itself is useful for this) and stir it up. Then let it settle for ten minutes or so.

The iodine will settle to the bottom so pour off the water and acid.

The iodine will still be contaminated with acid so you'll need to add water and pour off several times to get out most of the acid.

Filter it and now you have a solid plug of iodine.

It's usable as-is for most purposes but you can purify by placing it in a beaker with a ice-filled round bottom flask on top. Then heat the beaker. The iodine will vaporize and deposit on the flask.

A cool reaction is to take some iodine and pour magnesium powder over it. It will react to form a purple cloud of iodine vapor. If it doesn't react quickly enough, just add a drop of water.

While the iodine vapor is cool, it's also toxic and this reaction should be performed outside.

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    22 Discussions

    Is there a way to make potassium iodide without using iodine? Could I make it with potassium hydroxide?

    I dont think hydrogen sulfide is created in this reaction
    NaI + NaIO + H2SO4 = I2 + {-}2HI + Na2S + H2O

    3 replies

    It is, after all, what do you get when you react sodium sulfide with sulfuric acid?

    Ahh indeed then H2S will be produced, but if equation balanced and correct proportions used then shouldn`t be any nasty smelling S gases.
    But again I guess amateur chemists can do mistakes in stoichiometry

    No, if the correction proportions are used the reaction wouldn't behave that way. The moment a tiny portion of Na2S is created it would react with the sulfuric acid and generate H2S. This would then produce Na2SO4 and stop further reaction since you'd consumed the sulfuric acid faster than what your ideal reaction asserts.

    The chemicals don't just hang around and wait for everything to complete. If multiple competing reactions can happen then they will happen. They don't stop and behave nicely just because you use the correct proportions. This is why H2S is always a danger.

    Nurdrage isn't Hydrogen sulfide extremely toxic, the lethal dose in 1L of air is 800 mg?! How to you neutralize it?

    I am thinking of making eventually iodo vanilla extract. I will buy potassium iodide, ethyl acetate, and others like 500 ml of lugar iodine. This youtube video shows how to make it.

    Hey Nurdrage have you ever used Povidone iodine extraction. I am thinking of doing this in my lab. All I need is boiling chips and Iam all ready. I have extracted iodine from tinture of iodine with 25% HCl, 35% H202 and tinture of iodine!

    You can avoid the hydorgen sulphide (made by the reduction of sulpheric acid by the hydrogen of hydrogen iodide) by the use of manganese dioxide.

    1 reply

    don't have to, check out my other iodine video where i make it from hydrochloric acid and hydrogen peroxide.

    did you know most stores like walmarts sells iodine tablets in the camping section!!! anyway nice vid ill give you a 5.00 rating

    1 reply