Australia's Science Forum

We have had a disaster this morning. Having used buckets of sugar and tons of sulphuric acid we now have dozens of beakers contaminated and not one of them worked. (I am exaggerating) However we haven't been able to get this to work. We have wet the sugar used the proportions suggested in CSIS everything I and our chem teacher can think of.
Any idea gratefully accepted!

We had trouble getting ours to work, with some old acid that had been around quite a while, so I bought some new acid and it works a treat. Not sure if it was just old, or contaminated in some way........it was a bit brown

We couldn't get ours to work either.
I'm assuming it was the very old conc. acid.

Interesting. Ours is very old too. I haven't bought any in the 10 years I have been here. Of course I need it today! Anyway I have done it again with proportions I found on line and it worked!

lol don't laugh I actually had a teacher last year for a end of term prac., ask for a bucket, 2lt conc. HCL and 2-4kg sugar. All I could say was you are kidding NOOOOOOOOOOOO The reply was I'll do it on the oval NOOOOOOOOOOOOOOOOO

So what proportions did you use, Rae? I might give it another go.

Last year, I wanted to use up some old stock and that didn't work with the sugar. Then we filled a 150ml beaker about 3/4 of the way up with sugar and poured about 50ml of new conc acid to it. It took a little while to start working and then it shot up. I still have it on show since I don't know what to do with it.

I ended up doing 70g sugar and 70ml of sulphuric acid. I gave it a stir and it went black and I thought it wasn't going to work again. So I went in search of different sugar and when I came back it had worked.

Sulfuric acid goes off in time
Sometimes it does take a while to get a reaction then suddenly its WOW !!
Time and patience

I do this demonstration outside the labs on a grassed area that has a flat patch of dirt. I use a large metal tray with a layer of sand on it. I place a 400ml beaker almost half filled with sugar on this bed of sand on the metal tray and then pour conc.sulfuric acid over the sugar till there is about a 1cm layer of acid on top. Just stand back and watch. Make sure kids are well away from smoke produced (just in case there is an asthmatic child in class). Have just recently done this for two classes. The acid I used was pretty old (really old) but clear, syrupy and stored in a brown glass bottle. Took about five minutes or so for the reaction to complete. The burnt column was about twelve inches high (30cms). Don't forget the large tongs for handling purposes in case it falls over. I have never stirred the two ingredients together. It is much more interesting just to observe how the acid turns the sugar first yellow, then brown and then black with smoke coming off, and then like magic to start rising into the air out of the beaker. Afterwards, I put the entire setup into the fume cupboard and the following day I extract what I can from the beaker and wrap securely in newspaper with sticky tape and put into the garbage bin.
If your acid is brown, is it stored in black plastic? I have some stored in a black plastic container and it has changed colour and has flecks of black through it from the plastic container. The acid still works though.

My acid was stored in clear glass and had been here for a long time. I thought it would be perfect for the sugar experiment, to use it up out of the way, but it was not to be. Just made a black sticky mess that was a problem to clean up.

The chem teacher ended up warming up the beaker and then adding hot water to the top of the sugar in the beaker. The reaction was almost instant!

I use a gas jar and stand a large glass rod in to make it easier to clean the muck out when finished

Ours hasn't given very good results in past years either.

This year we ordered some fresh acid and it worked beautifully.

The teacher also tried it with castor sugar, and then pure icing sugar, getting a better reaction each time.

It was one of those great occasions when the class on the other side of the fume cupboard, plus other teachers, all crowded around to see the fun!

best option to clean up said beaker after amazing sugar and acid reaction?? I am currently soaking hoping this will help but the teacher did the prac while I was away and it was pretty crisp when I go back

Wrap it up in newspaper and bin it!!

Does anyone still do this? Had a request from a grade 9 teacher to do this as a demo.

I've had teachers do this as a demo for Year 12 in recent times, but never for any junior groups. I know they do it here, but not sure who for - only been here two weeks. Make sure it is done in a fume cupboard and leave it there overnight with the fan running before handling.

Yes, we still do it here but only as a demo in the fume hood. It is a high risk prac, so our head teacher decides on a case by case basis whether he will approve the class teacher to conduct it or not.

It's demo ONLY and we use small amounts. Done outside and clean up with lots of water and bi carb soda before wrapping up in newspaper and bin it.
Some teachers try to do big but it's not best with the fumes.