[dahoog]

I am a high school student but due to the complex nature of what I am asking, I thought it was more appropriate to ask these questions here

I have been currently conducting tests which involves phosphate determination in the soil. However I now have to write a 4000 word essay on these. As a part of the essay, I have to describe the chemistry involved (with references). I am having problems with the analytical part of the chemistry.  I would be extremely grateful if someone could either answer my questions and/or direct me to resources that might help me.

What is occurring when the phosphate reacts with acidified ammonium molybdate? I know this results in a alpha keggin ion however I am unsure as to how to deal with it. Can I treat it as a complex ion? This is then reduced to a beta keggin ion. What is the difference between alpha and beta keggin ions?

Any help would be greatly appreciated.