Improvements in the production of concentrated nitric acid from dilute solutions

摘要

320,125. Johnson, J. Y., (I. G. Farbenindustrie Akt.-Ges.). July 7, 1928. Nitric acid.-Concentrated nitric acid is prepared from dilute nitric acid by extraction with liquid nitrogen peroxide at 30-60‹ C. in a closed vessel whereby considerable pressure is attained. The upper layer of nitrogen peroxide is removed and may be distilled to obtain concentrated nitric acid or may be cooled to form two layers, the lower one containing the bulk of the nitric acid and the upper one mainly nitrogen peroxide which may be used again for extraction. Waste acids such as those obtained in nitrating cellulose or in making dyes or intermediates may be treated.