Carbohydrate and Sulfuric Acid

Images of a demonstration by Eric Muller

Concentrated sulfuric acid when stirred into sugar produces a steaming black carbon foam.


When you add concentrated sulfuric acid to sugar the result is interesting. The sulfuric acid dehydrates the carbohydrate sugar, removing the water and heating it into steam leaving behind a carbon foam.

Danger. Do not do this demonstration. Concentrated sulfuric acid is dangerous to handle. The fumes produced in this experiment are hot steam rich in sulfuric acid, do not breathe the fumes, a fume hood is needed. Notice how Eric is wearing goggles and doing the demonstration outdoors. We show you these images so that you can see the demonstration without doing it.

Eric puts on his safety goggles.

Eric pours a few hundred milliliters of granulated sugar into a beaker. He then adds enough water to dampen the sugar.

Eric adds concentrated sulfuric acid to the damp sugar mixture.

Eric stirs the acid into the sugar. At first nothing happens, then the sugar turns brown, and then black. As soon as it begins to steam...

Eric pulls back, a cylinder of black foam rises from the beaker. The steam smells of cooked sugar and is very irritating since it is rich in hot steaming acid droplets.

The cylinder continues to grow and steam.

A long black cylinder of carbon foam protrudes from the beaker.

What's Going On?

The sugar, a carbohydrate such as C6H12O8, is mixed with the sulfuric acid, H2SO4.

The sulfuric acid dehydrates the carbohydrate removing water H2O and leaving behind carbon, C. The hot steam creates bubbles in the carbon making a carbon foam. When the foam cools it is stiff. The foam should be handles while wearing gloves since it might contain sulfuric acid.


The clouds of Venus contains sulfuric-acid-rich droplets. Carbon rich lifeforms should wear protective clothing when visiting Venus. Or they might experience the dehydrating effects of interaction with sulfuric acid.


Johnny was a chemist's son,

Johnny ain't no more,

What Johnny thought was H2O,

Was H2SO4.


Do Not Do this Demonstration



Scientific Explorations with Paul Doherty

© 2004

23 June 2004