Yes it is. It is not a two sentence explanation. I am also not going to just copy the stuff from a book (because A it is illegal and B I have no desire).
Just get any Industrial Chemistry book, it will explain it in great detail, more then you probably want to know.
The one I have is 16 years old and it talks about it, so just check your local libraries for any Industrial Chemistry book, since it is not a short quick answer.