Extractor question

Cathy,

The extractor is nifty! My question is: what is the solution used to extract the elements from the soil? Is it mostly water? Water is a universal solvent but some interesting compounds might not want to "let go" of the soil. Is there something in the water, maybe a surfactant like detergent, so that things that do not dissolve easily in water are also extracted?

I think that home-built, purpose-made equipment is very cool. Thanks for showing it to us,

Gerty