This is actually illegal in the UK!! I think I've heard of similar
mixtures before, but the liquid soap is often suggested over here as a
"green" insecticide. Typically in the form of Washing-Up Liquid (Fairy
and the such). A recent law in the UK says that you cannot use a
chemical for a use not listed on the bottle,etc. Obviously, this can be
a useful thing - stopping people doing some quite harmful things, but it
does mean that you cannot use Fairy Liquid for anything except washing
dishes!!!
I believe the phrase "The Law is an Ass" is relevant
Richard Marsden