after reading various posts, I was still confused about the actual acidity of ReaLemon and ReaLime. Below is their response to my querry:
Thank you for contacting us about ReaLemon. Your comments and inquiries are appreciated because they provide valuable feedback about our brands.
Here is some information about the acidity of Realemon and Realime:
ReaLemon Acidity (as citric acid) 49-51 g/L
Cadbury Schweppes has been making great brands that people love for more than 200 years. We are proud of our family of beverage and confectionery products and are committed to providing a wide range of choices for all individuals.
(a subsequent exchange prompted the info that the acidity for ReaLime is the same)
I'm no scientist, but I intrepret the Brix to mean acidity and between 6.5 and 8% -- which seems a rather wide range.