Acidification of urea solution.

Question

What does "acidification of urea solution by using Nitric acid to pH 1" mean?

Answer 1

Urea normally has an alkaline pH, i.e. a pH >7.  Acidification using nitric acid means that you add nitric acid (HNO₃) until the pH reaches the desired pH.  In this case, that would mean to add HNO₃ until the pH was a value of 1.