This site provides a useful applet that demonstrates countercurrent extraction. The explanation of the method is short, but good. The level is appropriate for undergraduate students. The Applet itself is well designed and provides a useful exercise for students around which homework or small-group waork could be developed. The use of color is particularly helpful. The same author has a larger collection of applets about instrumentation and other analytical concepts in the ASDL collection. It can be found by searching the ASDL library using ‘applets’ as the keyword, or going to the site: http://www.chem.uoa.gr/applets/Applet_Index2.htm
The website is available here .