Just thought I'd throw out a couple of comments here.
Simple Green is great stuff but must be rinsed off completely or it will cause corrosion.
Mineral Spirits (paint thinner) is a great solvent that's not overly toxic. After soaking a part such as a chain, you can dump the used stuff in an old gas can or similar and set aside. After a few days the black sludge will settle down to the bottom of the can so you can pour off the clean stuff on top to be used again and again.
Ed