Laser Raman spectroscopy was used to study the nu //1 (A//1) band of aqueous potassium nitrate solution. The purpose was to establish the relationship between solution structure, nucleation and growth. Two bands were determined that exist at 1049 cm** minus **1 (the free nitrate ion) and 1050. 5 cm** minus **1 (a more ordered species). The band at 1050. 5 cm** minus **1 increased in magnitude as concentration was increased into the supersaturation region. Solutions containing 200 ppm Cr**3** plus were also studied and this impurity was found to suppress the formation of the species at 1050. 5 cm** minus **1.