Subject: What would be a good mixture for showing fractional distillation?

I am trying to find a good mixture (materials and proportions)for teaching 
my students how to fractionally distill two liquids. I want them to have 
this knowledge and skill before they begin an Identification of Unknown 
Substances unit. I have used ethyl alcohol and water in varying 
proportions with little success, and the department chair is starting to 
get grumpy with the volume of resources I am using.
Any help would be greatly appreciated.
Thank you.

Re: What would be a good mixture for showing fractional distillation?