J.R. Marier

Determination of cyanate, and a study of its accumulation in aqueous solutions of urea☆

Abstract Cyanate accumulation in aqueous solutions of urea was measured by means of a spectrophotometric method of improved sensitivity. At 25°C, cyanate accumulation initially occurred at a rate of ca. 0.07 mmole of NCO/liter/day/mole of urea, but the rate of accumulation decreased progressively (especially at higher urea concentrations) and a maximum cyanate level was reached in about 60 days. At a given urea concentration, the maximum cyanate level at 25° was ca. 60% of that obtainable at 38° (7 days), and ca. 23% of that obtained at 85° (50 min). The presence of traces of ammonia in some lots of reagent-grade urea is believed to stimulate initial cyanate accumulation. Cyanate accumulation was prevented by storage of neutral solutions of urea (prepared at temperatures not exceeding 25°) at 5°, or by buffering the urea solutions at pH 4.7.