Evaporation of toxic chemicals in a hot water bath

Good afternoon,

In our school, a Y12 student is doing an experiment with three replicates of four different chemicals and water. The goal is to recover a layer of oil that forms when these chemicals come into contact with the oranges.

The chemicals are: ethanol 96%, petroleum spirit, propanol and butanal.

She has previously poured 100 ml of each chemical into a conical flask and mixed it with smashed oranges. She then left them in a water bath at 40ºC for two hours. All chemicals but ethanol have been handled under a fume cupboard.

In the following step, she needs the aqueous solution of each conical flask to evaporate. Since this process is very slow at room temperature, she plans to transfer with a pipette the aqueous solution into a new bottle she will place into a water bath at 95ºC. The bottles will be left at that temperature with the lids off for several hours to ensure evaporation.

My question is: is it safe to leave the baths on at 95ºC for several ours with the lids off? Should we put the baths inside the fume cupboard, then move it to a safe place where there's no people around, and keep them there for several hours? (that is, inside the school premises but outside the building where they give lessons).

Any feedback is highly appreciated.

Thank you.
I think a normal water bath set a 95 C for a while will soon run dry so you will need some of those spheres that minimise evaporation.
Yes, that's true... either we put a lot of water or we keep refilling the bath... I've thought about the oven, but I don't think that's a good idea, either.
Here's what's left:


W1 W2 and W3 correspond to water mixed with oranges. It didn't evaporate because the temperature of the baths was around 65ºC...
We left the bottles with the lids off in the baths for about 7 hours. There's barely any liquid left in the ones that had the chemicals (butanal, propanol, petroleum spirit, cyclohexane and ethanol).