I went off of a maximum assumption for calculating the ΔHΘ of a strong acid base reaction, which would be -57.1 Jmol-1K-1, and found a pKa under standard conditions of 5.67 for Diethylhydroxylamine (DEHA). Using the Van't Hoff equation, where T1 and K1 would be our standard conditions, T2 would be the temperature we wish to know the pH value of.

I then made an excel with headers as follows :

T2 (°C) _ T2 (°K) _ 1/T2 _ (1/T1-(1/T2) _ K2/K1 _ K2 _ ln(K2) _ pH

pH was then calculated via pOH (steps below) and use the formula to cover a range of temperatures from 10-150.

Then I made a table of a range of concentrations of DEHA under standard conditions.

After having a method for doing temperature ranges and concentration ranges I combined the two.

Knowing the Ka value at specific temperatures,

[OH-]^2 = [DEHA] * Ka

sqrt[OH-]^2=[OH]

pOH=-log10([OH])

pH = 14-pOH

Ended up with a massive table, going to be running an experiment with a boiler and some probes to test my theoretical values in the coming week.

Probably not the greatest explanation of how I got there. Basically effort and caffeine...

I'll check with my boss and see if I can post my excel or if it is company property.