1801. Potassium discovered by Sir Humphry Davy.
1802. Examples of Heliotypes, by Wedgwood and Davy, exhibited at the Royal Institution, and process published.
1803. Palladium discovered in platinum by Dr. Wollaston.
1808. Strontium obtained from carbonate of strontia by Sir Humphry Davy.
1812. Iodine discovered by M. D. Curtois, of Paris.
— Nitrate of silver and albumen employed by D. Fischer.
1813. Ditto investigated by M. Clement.
1814. Joseph Nicéphore de Niépce commenced experiments with the hope of securing the pictures as seen in the camera-obscura.
— Iodide of silver made by Sir H. Davy.
1819. Sir John Herschel published the fact that hyposulphite of soda dissolved chloride and other salts of silver.