[takeABow]

Introduction
Hi, I am working on updating my school's Liquid-Liquid-Extraction Experiment (for Unit Operations Lab).  The old process used several carcinogenic and/or toxic chemicals.  I have been tasked with designing the new process using as much of the new equipment as I can.  However, when I was brought on to the project the replacement chemicals did not extract as nicely as we would have hoped (that is to say - not at all).  I am good at experimental design and data analysis, but I don't know of a nice extraction process that will fit the bill for what I need.  Any help would be appreciated!

What I have
I have an extractor with two inputs, one of which is hooked to the building's water supply - water must be one of the materials involved in the extraction.
I have a 55 gallon drum of 200T mineral oil, which would be convenient to extract from or to since we wouldn't need to buy more.  I am not bound to it however.

What I Need
(A), dissolved in (B), will extract most/all into (C).
Either B or C must be water. 

Everything must be:
Safe for students (nothing hazardous)
Environmentally Friendly

Preferably whatever A is would have some color to it so the students can see the extraction occur.

Any suggestions?

[jusy1]

I don't know if you still need an opinion but what do you think about using methyl yellow for example?

It has a solubility in water of 13.6 mg/L and a log P (o/w) = 4.58

[takeABow]

It would be perfect, but Methyl Yellow's status as a carcinogen probably rules it out.

I do appreciate the suggestion!

Food safety regulations put its content limit at 1.6 PPM, which is a bit too small for what I'm looking for.

[jeffrey.struss]

Are you planning on having the students eat the stuff that comes out of the extraction? Otherwise the food safety limit is rather useless as it is the safety limit based on oral consumption and has little relevance to cutaneous or other methods of exposure.

Additionally, it is hard as heck to find chemicals that don't have SOME sort of warning.

EDIT: What about bromocresol green? it is sparingly soluble in water but soluble in benzene, which would indicate some non-polar solubility. Though it is listed as highly soluble in ether. It is listed as not being carcinogous nor anticipated as being carcinogous.

[takeABow]

I will have to test bromocresol green.  Sounds like it might do the trick.  I'll have to order some right away and see what goes.

I am still open to more suggestions, however. 

Thanks for the ideas!

[jusy1]

I think you can also consider annatto, used as a food coloring agent.

It contains norbixin (water soluble) and bixin (fat soluble).