Thank you for your response. My apologies, I should have made that more clear. The density of the fluid that the acid is being added to is 1.08 due to salt content. The density of the acid depends on the concentration (we usually get 20 or 15%). When the acid is added, the density of the fluid increases to 1.14.
Basically, we have a coriolis meter measuring the density of the incoming fluid, acid of an unverified concentration is added, and another coriolis meter measures the density again. I want to be able to use the measurements from the two coriolis meters to calculate the final acid concentration.
My first approach was to take 1.14 - 1.08 = .06 and use a curve fit from this lookup table http://www.starch.dk/isi/tables/hcl.htm
to interpolate the concentration. This method gives "reasonable" results but my gut tells me I'm missing something.