there are a few chemical toilets on the market a name and model would help.
I am assuming it is a Thetford so go to the Thetford website.
www.thetford-europe.com click on service follow through toilets cassette toiles and find the repair instruction PDF it covers all models. Down load the pdf and look for your model it might be that floating ball is from your cassette. When downloaded copy it to a cd if you take a laptop on hols then you have repair information on sites so to speak
Good luck. If you can't find anything on that then contact Thetford via their online form.
Bob UK
September 2014