The Spectrophotometry of Nitrate Solutions in Aqueous Sulphuric Acid

Abstract

The ultraviolet spectra of solutions of potassium nitrate in aqueous sulphuric acid have been studied. Three absorptions, those due to the species NO₃^-, HNO₃, and NO₂⁺, have been found. From this study a semiquantitative picture has been developed of the distribution of the total nitrate between these three species. It was found that in the sulphuric acid concentration range 0-15% by weight, the dissolved nitrate existed as nitrate ion and that from 15-70% sulphuric acid, nitrate ion, and molecular nitric acid were present in comparable amounts. In the sulphuric acid concentration range 72-82% nitric acid accounted for the total dissolved nitrate and as the sulphuric acid concentration was increased from 82-90% nitric acid was converted to nitronium ion.