The following elements, twenty-eight in number, were known before 1800: ELEMENTS KNOWN BEFORE 1800. 1. Copper Known to Ancients. 2. Gold ” ” ” 3. Iron ” ” ” 4. Lead ” ” ” 5. Silver ” ” ” 6. Tin ” ” ” 7. Carbon ” ” ” (But three forms not identified until 1786–1800.) 8. Mercury Known to Ancients. 9. Antimony Fifteenth Century. 10. Bismuth ” ” 11. Zinc ” ” 12. Phosphorus 1669 13. Arsenic (Isolated) 1697 ” (Studied) 1733 14. Cobalt 1733 15. Platinum 1735–1748 16. Nickel 1751 17. Hydrogen 1766 18. Nitrogen 1772 19. Oxygen 1774 20. Manganese (Studied in compounds, isolated at unknown date) 1774 21. Barium 1774 22. Tungsten 1781–1785 23. Molybdenum 1782 24. Tellurium 1782–1798 25. Strontium 1790 26. Yttrium 1794 27. Chromium 1797 28. Beryllium 1798 Four additional elements were known to exist before that date, but they had not been isolated and identified. These are:— ELEMENTS KNOWN BUT NOT ISOLATED OR EXAMINED BEFORE 1800. Chlorine {Compound known 1774 {Isolated and studied 1810 Titanium {Known in compounds 1791 {Isolated 1824 Uranium {Known in compounds 1789 {Isolated 1824 Zirconium {Known in compounds 1789 {Isolated 1824 The following elements, forty-nine in number, have been discovered since 1800:— ELEMENTS DISCOVERED SINCE 1800. 1. Niobium 1801 2. Vanadium 1801 3. Tantalum. Studied about 1802–1803 (Not yet isolated.) 4. Cerium 1803 5. Iridium 1803 6. Osmium 1803 7. Palladium 1803 8. Rhodium 1803 9. Potassium 1807 10. Sodium 1807 11. Calcium 1808 12. Boron 1808 13. Silicon 1810 14. Iodine 1812 15. Cadmium 1817