General methods of test for pigments - Part 19: Determination of water-soluble nitrates (Salicylic acid method)
Document Number: ISO 787-19:1974 File Size: 274 kB Language: English Provider: ANSI Shipping: Available for download - Link will be provided in My ComplianceOnline section
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This document specifies a spectrophotometric method. The principle of the method consists in that the nitrate present in the extract of the sample is used to nitrate salicylic acid in sulphuric acid medium. The nitro-compound formed is of an intense yellow colour in alkaline solution and the colour is measured spectrophotometrically at a wavelength of 410 nm. ISO 787/13 specifies a method using Nessler's reagent. The two methods may not necessarily give the same result; work is being carried out to compare the two methods.
