# Help me recall this chemistry demonstration

**URL:** <https://boards.straightdope.com/t/help-me-recall-this-chemistry-demonstration/675669>\
**Category:** In My Humble Opinion\
**Created:** [December 6, 2013, 2:10pm UTC](https://boards.straightdope.com/t/help-me-recall-this-chemistry-demonstration/675669 "2013-12-06T14:10:53Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![Patty\_O\_Furniture](https://avatars.discourse-cdn.com/v4/letter/p/96bed5/32.png) [@Patty\_O\_Furniture](https://boards.straightdope.com/u/Patty_O_Furniture)\
**Post date:** [December 6, 2013, 2:10pm UTC](https://boards.straightdope.com/t/help-me-recall-this-chemistry-demonstration/675669/1 "2013-12-06T14:10:53Z")

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Calling all chemical-science-type people,

I remember watching a demo in 8th grade chemistry wherein the teacher poured some liquid into a beaker that was about a quarter full of ordinary white sugar. Within seconds, an enormous black stalk grew out of the sugar/liquid mixture. It got so tall the teacher had to hold it with tongs to keep it from toppling over. I think it eventually reached a height of about a half meter.

What was the liquid, and what was the experiment meant to demonstrate?

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**Author:** ![Shark](https://avatars.discourse-cdn.com/v4/letter/s/73ab20/32.png) [@Shark](https://boards.straightdope.com/u/Shark)\
**Post date:** [December 6, 2013, 3:04pm UTC](https://boards.straightdope.com/t/help-me-recall-this-chemistry-demonstration/675669/2 "2013-12-06T15:04:16Z")

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Concentrated sulfuric acid. It is an exothermic dehydration reaction

> **[Perform the Sulfuric Acid and Sugar Chemistry Demonstration](https://www.thoughtco.com/sulfuric-acid-and-sugar-demonstration-604245)**
>
> Ordinary table sugar and sulfuric acid react to produce a growing black column. This demonstration is an exothermic reaction and dehydration reaction.

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**Author:** ![Canadjun](https://avatars.discourse-cdn.com/v4/letter/c/76d3ee/32.png) [@Canadjun](https://boards.straightdope.com/u/Canadjun)\
**Post date:** [December 6, 2013, 4:37pm UTC](https://boards.straightdope.com/t/help-me-recall-this-chemistry-demonstration/675669/3 "2013-12-06T16:37:48Z")

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Don’t EVER try it in a plastic container! Says one who liked to steal chemicals from his high school chem lab and play with them at home several decades ago. :eek:

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**Author:** ![Patty\_O\_Furniture](https://avatars.discourse-cdn.com/v4/letter/p/96bed5/32.png) [@Patty\_O\_Furniture](https://boards.straightdope.com/u/Patty_O_Furniture)\
**Post date:** [December 7, 2013, 12:28pm UTC](https://boards.straightdope.com/t/help-me-recall-this-chemistry-demonstration/675669/4 "2013-12-07T12:28:36Z")

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Yes that’s it! What’s the purpose if adding a little water first? I do t remember that part.

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**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\
**Post date:** [December 7, 2013, 2:03pm UTC](https://boards.straightdope.com/t/help-me-recall-this-chemistry-demonstration/675669/5 "2013-12-07T14:03:56Z")

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> [@Patty\_O\_Furniture](#):
>
> Yes that’s it! What’s the purpose if adding a little water first? I do t remember that part.

I don’t recall that, but maybe pre-dissolving the sugar helps kick it off faster. Liquid-liquid reaction instead of liquid-solid.

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**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\
**Post date:** [December 7, 2013, 2:15pm UTC](https://boards.straightdope.com/t/help-me-recall-this-chemistry-demonstration/675669/6 "2013-12-07T14:15:40Z")

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I should have mentioned that some stuff isn’t all that soluble in concentrated sulfuric acid.

And, adding a little water will heat things up quickly.

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**Author:** ![Bill\_Door](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)\
**Post date:** [December 7, 2013, 4:20pm UTC](https://boards.straightdope.com/t/help-me-recall-this-chemistry-demonstration/675669/7 "2013-12-07T16:20:51Z")

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> [@Ruken](#):
>
> I should have mentioned that some stuff isn’t all that soluble in concentrated sulfuric acid.
> 
> And, adding a little water will heat things up quickly.

But add acid to water, not the other way around. You don’t want to get splashed with hot sulfuric acid.

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**Author:** ![Billy-o](https://avatars.discourse-cdn.com/v4/letter/b/e8c25b/32.png) [@Billy-o](https://boards.straightdope.com/u/Billy-o)\
**Post date:** [December 7, 2013, 4:29pm UTC](https://boards.straightdope.com/t/help-me-recall-this-chemistry-demonstration/675669/8 "2013-12-07T16:29:54Z")

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Just a cautionary note: be aware that the reaction gives off some acrid-smelling fumes, so do this in a well-ventilated place (or better yet, a fume hood). And have fun! 🙂