From a notebook that he kept at this time are analytical results that document the discovery of nitrous oxide and that illustrate the law of multiple proportions:
"When two elements combine and form more than one compound, the masses of one element that react with a fixed mass of the other are in the ratio of small whole numbers."
|Compound||Percent N||Percent O||Grams of N|
1.00 g of O
"In the present state of our knowledge, it would be useless to attempt to speculate on the remote cause of the electrical energy . . . ; its relation to chemical affinity is, however, sufficiently evident. May it not be identical with it, and an essential property of matter?"Davy must have known of Lavoisier's suggestion that the alkali earths were oxides of unknown metals. At first, he tried to separate the metals by electrolyzing aqueous solutions of the alkalis, but this yielded only hydrogen gas. He then tried passing current through molten compounds, and his persistence was rewarded when he was able to separate globules of pure metal by this means. His first successes came in 1807 with the separation of potassium from molten potash and of sodium from common salt.(6) He described potassium as particles which, when thrown into water, "skimmed about excitedly with a hissing sound, and soon burned with a lovely lavender light." Dr. John Davy, Humphry's brother, said that Humphry "danced around and was delirious with joy" at his discovery. These results were presented in the Bakerian lecture of November, 1807.(8)
Through electrolysis, Davy eventually discovered magnesium (Magnesia, a district in Thessaly), calcium (calx, L for lime), strontium, and barium in 1808.(10) For all these discoveries, much groundwork had of course been done by others. Thus, Scheele had distinguished baryta from lime in 1774, and Berzelius and Pontin had prepared calcium amalgam by electrolyzing lime in mercury. But Davy was able to isolate the pure metals.(6)
Davy utilized the reducing power of potassium to prepare boron, and he developed the method of separating potassium from sodium based upon the insolubility of potassium perchlorate and the solubility of sodium perchlorate in 97% alcohol.(1)
3 Cl2 + 2 NH3 ------> 6 HCl + N2He exposed the gas to white-hot carbon in an attempt to remove the oxygen as carbon dioxide. He was never able to produce oxygen or any compound known to contain oxygen, and he finally concluded that it was an element. (12) He called it "chlorine" after the Greek "chloros" meaning yellow-green, the same association with color as found in "chlorophyll".
By a similar series of experiments, Davy showed in 1810 that muriatic acid or marine acid was a compound only of hydrogen and chlorine, and contained no oxygen. For example, he found that two volumes of muriatic acid react with mercury to give calomel and one volume of hydrogen:
2 HCl + 2 Hg ------> Hg2Cl2 + H2This put an end to Lavoisier's theory that oxygen was an essential constituent of acids.
Davy first made iodine pentoxide, a colorless, odorless, crystalline substance of high density in 1815. It is a strong oxidizing agent, and with oxidizible substances sometimes detonates.(3,4)
I2O5 + 10 H+ + 10 e- ------> I2 + 5 HOH
SiO44- + 4 H+ ------> SiO2 + 2 HOH
Davy twice opposed the election of Faraday to fellowship in the Royal Society. At one point he objected to honoring Faraday for achieving the first liquefication of chlorine, claiming that he himself deserved credit for the feat. Another time, Davy said his opposition was due to his belief that William Wollaston (1766-1828) had preceded Faraday in discovering electromagnetic rotation. Perhaps Davy had simply become envious of his (successful) former assistant. Faraday did finally become a Fellow of the Royal Society in 1824.(7)
In 1802, Thomas Wedgwood in cooperation with Sir Humphry Davy published a paper entitled "An Account of a Method of Copying Paintings on Glass, and Making Profiles, by the Agency of Light upon Nitrates of Silver". The pictures made by this process were very temporary. As soon as the negatives were removed the pictures turned black.(5)
Davy was knighted in 1812. Three days after being knighted, he married a rich widow, Jan Apreece. Davy along with his wife and his assistant, Michael Faraday, toured Europe from 1813 to 1815. Upon their return to England, Davy invented his miner's safety helmet. The lamp of this safety helmet would burn safely and emit light even when there was an explosive mixture of methane and air present. Davy did not patent the lamp. This error lead to later false claims by locomotive engineer George Stephenson that it was he that invented the miner's safety helmet, not Davy.(2)
In 1825, Hans Christian Oersted first successfully isolated aluminum in a pure form. Sir Humphry Davy had previously been unsuccessful at such attempts. It was Davy who named the element "aluminum", the name used in the United States. The rest of the world uses the term "aluminium".
Among Davy's other accomplishments are the introduction of a chemical approach to agriculture and the tanning and mineralogy industries. He designed an Arc Lamp and invented a process that could be used to desalinate sea water. He also designed a method whereby copper-clad ships could be protected by having zinc plates connected to them.
In 1827, Davy became seriously ill. The illness was later attributed to his inhalation of many gases over the years. In 1829 he made his home in Rome. While in Rome, he had a heart attack and he later died on May 29, 1829 in Geneva, Switzerland.
Davy's qualitative work was excellent but this could not always be said for his quantitative work. He was quick to make decisions and easily distracted. In his life time he went after many honors and won many of them. He had great perception, was good in the laboratory, but was very erratic at times.(5)
2. David Abbot, Biographical Dictionary of Scientists - Chemists, Peter Bedrick Books, New York, NY, 1983, pp. 35-36.
3. Sidgwick, Chemical Elements and Their Compounds,
4. Jolly, Chemistry of the Nonmetals
5. Cowles, Cowles Encyclopedia of Science, Industry, and Technology, Cowles Book Company, Inc., 1969, p.439 & 584.
6. CRC Handbook, 1962
7. D.J. Boorstin, The Discovers, Random House, New York , NY, 1983, p. 165
8. Toon and Ellis, Foundations of Chemistry.
9. Brady and Holum, Fundamentals of Chemistry.
10. Atkins, General Chemistry.
11. Dampier, History of Chemistry, 4th Ed., Cambridge, UK, 1943, p. 203
12. Leicester and Klickstein, Sourcebook in Chemistry, Harvard University Press, Cambridge, MA, 1968, pp. 243-258.
13. D. Van Nostrand, Van Nostrand's Scientific Encyclopedia, D. Van Nostrand Company, Inc., 1958, p. 478.