There is a thread here in the library
that lists several PDFs from a site called "The Beverage People" They created a pdf on Brine
Making. This paper talks about pH of a heavy brine. I tend to follow their recommendation and make sure my brine is about pH 4.7.
I have lots of Citric, Malic, and Tartaric acid laying around for winemaking, so I add a small pinch of one of these till my pH lowers to 4.7. I do not like to use the whey. They whey is a living thing in my mind, and as such, the whey is getting more acidic over time. (This may not be true, or even important, but i cannot bring myself to use the whey.)
Sometimes I have lowered too much, then I have to add water, and then more salt.
Bottom line is that my Brine has a Specific Gravity of about ~1.150 and a pH of 4.7