To simulate the action of gastric $\ce{HCl}$, we have titrated 100 ml of a meal with 0.1 N $\ce{HCl}$. To plot the data, use (R-code)
vol = read.table("http://menne-biomed.de/uni/volph.txt",sep="\t",header=TRUE)
plot(vol$vol,vol$pH,pch=16,type="l",main="Titration of 100 ml meal with 0.1 N HCl")
I am trying to determine, for example, how much 1N $\ce{HCl}$ I need to add to get a pH of 1.5; if I understand correctly, I have to fit the Hasselbalch equation.
Being a statistics guy, the numerics is no problem, I just do not understand how to get the terms in that equation together with my data.