To follow on from my post a few minutes ago... OK I've found my previous post which was nearly a year ago, and the link to the information on acidity of saliva substitutes didn't work! So it looks like I changed from Biotene a year ago.
For information on acidity of saliva substitutes try this link
http://www.googlesyndicatedsearch.com/u/ukmi?q=right+product&sa=Google+Search and click on the top link which should be called 'Saliva substitutes - UKMi' this should open a word document. It has been updated in February, since I looked at last November, and guess what, Biotene is now listed as being acidic. I hope you find this helpful.
The information is provided by UK Medicines Information (UKMi)which is a UK NHS pharmacy based service.
http://www.ukmi.nhs.uk/ukmi/about/default.asp?pageRef=1