[lllhills]

I'm following these lab procedures: http://employees.oneonta.edu/knauerbr/chem226/226expts/226_expt06_pro.pdf

Step 10 says to add Petroleum Ether to a solution on a hot plate. Instead of Petroleum Ether, I'm thinking of using Cyclohexane, since it effectively serves the same purpose. Regardless, aren't Petroleum Ether and Cyclohexane extremely flammable? Why do the procedures say to add it to a hot plate, when both are very flammable? In this lab, would it be safe to add it so a solution on a hot plate, or should take the solution off the hot plate and wait for it to cool before adding it?

[chenbeier]

It says to drop the petrolether to the solution, not on the hot plate. By accident it can happen, that drops hit the iron of the plate it self, what cause fire.  You can remove the beaker from the plate and add the petrolether outside and put it back after.  Instead of a hot plate you can use also a water bath, because the temperature is below 100° C.