1. Pogg. Ann., 12, 253–56 (1828). In 1812 John Davy obtained urea, but was unaware of it, by the action of ammonia and phosgene (Phil. Trans., Pt. 1, 145–46; 1812); he gives no details as to the source of the carbon monoxide used in the preparation of the phosgene.
2. Ann. Chim., 37, 330–34 (1828).
3. Quart. J. Sci., Pt. 1 (April–June), 491–92 (1828).
4. The process is described in the almost contemporary text-book of Edward Turner, the flrst professor of chemistry in University College, London: "Ferrocyanate of potash" is "made on a large scale in the arts by igniting dried blood or other animal matters, such as hoofs and horns, with potash and iron. By the mutual reaction of these substances at a high temperature, ferrocyanuret of potassium, consisting of one equivalent of the radical of ferro-cyanic acid … and two equivalents of potassium, is generated. Such at least is inferred to be the product; for on digesting the residue in water, a solution of ferrocyanate of potash is obtained. … When heated to 212° F., or even below that temperature, each equivalent of the salt parts with three equivalents of water, leaving one equivalent of ferrocyanuret of potassium. … On heating the dry compound to full redness in close vessels, decomposition takes place, nitrogen gas is disengaged, and cyanuret of potassium mixed with carburet of iron remains in the retort." ("Elements of Chemistry, etc.", 3rd edn., 658; London, 1831).
5. Wallach, O., "Briefwechsel zwischen J. Berzelius und F. WÖhler, etc.", i, 206 (Leipzig, 2 vols., 1901).