Paper, 'A cyanogen reaction of proteids' by J Gnezda Gnezda writes: 'When dry urea is heated to its melting point it gives off ammonia, and a substance called biuret (C2N3H5O2) remains behind. Biuret is decomposed by heat into ammonia and cyanuric acid (C3N3H3O3). G. Wiedemann discovered that on adding an alkaline solution of copper sulphate to cyanuric acid, a violet solution was produced. The same investigation showed that biuret gave a rose-red solution on treatment with copper sulphate and sodium hydrate.' Annotations in pencil and ink. Subject: Organic chemistry Received 19 December 1889. Read 20 February 1890. Communicated by Edward Albert Sharpey-Schafer. A version of this paper was published in volume 47 of the Proceedings of the Royal Society as 'A cyanogen reaction of proteids'. 1889