Preparation of Sulphuric Acid free from Nitric Acid

Abstract

FOR the analysis of the nitrate content of sea water, and for certain tests on alkaloids, it is necessary to have sulphuric acid free from all but the most minute amounts of nitric acid. After testing a number of British and foreign samples of pure sulphuric acid, Harvey¹ reported that he had found the ‘nitrogen free’ sulphuric acid specially supplied by the British Drug Houses, Ltd., to be satisfactory, though the ‘analytical reagent’ acid was not so. Even in the purest acid the reduced strychnine reagent of Denigès demonstrated the presence of nitric acid, which was estimated by extrapolation after adding known amounts of nitrate, reckoned as milligrams of nitrate nitrogen per cubic metre of sea water.