Conductivity variation on Caustic (NaOH) Dilution System

I am reading the drawing for an automatic caustic dilution system where 50% NaOH is diluted down to 20%. 


I was expecting to see a density sensor on the outlet to provide feedback to the dilution pumps for ratio-ing. i.e. To keep the density at 20% and prevent it from moving to say 19% or 21% by adjusting the amount of water. 


However, the vendor seems to have used a conductity sensor on the outlet instead. I am skeptical whether the conductivity of NaOH will vary a lot between 19% to 21%. Isn't it already fully ionized?


Thoughts? Will this work?


