Ten elements were discovered in antiquity; seventeen more were discovered pre- 1789, then fourteen years later four of the six Platinum Group Metals: Rhodium, Palladium, Iridium Osmium. By the end of the 19th century, forty-seven more were discovered, the remainder plus those synthesised coming in the 20th century.
‘Sir Humphrey Davy abominated gravy, he lived in the odium of having discovered sodium’, a clever Clerihew about Davy the self-taught chemist and pioneer of electro-chemistry, born Today in Penzance, Cornwall in 1778.(1)
Davy used Electrolysis, adding water to cleave chemical bonds with the aid an electric current to separate elements from their compounds. This Used a Voltaic Pile ‘sandwich’ of a damp cardboard disk between two metal disks that generated a weak charge to decompose the alkalis.(2)
His Electrolytic apparatus was simple-a Direct Current battery-connected to metallic electrodes dipped into a liquid containing the compounds Davy wanted to decompose.
In 1807 using this method he isolated the metal Potassium from Caustic Potash, now known as Potassium Hydroxide (KOH), the first to be isolated by electrolysis. Potassium is highly reactive in water, generating sufficient heat to ignite the Hydrogen emitted in the reaction.(3)
He then produced Sodium by electrolysis through molten Sodium Hydroxide (NaOH), caustic soda called Lye (not a plant salt), showing the two elements and salts to be different.(4)
In 1808 Davy isolated Alkaline Earth Metals from several minerals. He extracted Barium baryte, from probably Barium Oxide (BaO); from Lime, Calcium Oxide (CaO) or Quicklime he prepared Calcium. To isolate Strontium he used Strontite, Strontium Oxide (StO), and isolated Magnesium from Magnesia or Magnesium oxide (MgO).
At first he tried to dissolve various compounds in water but this was Electrolysed into Hydrogen and Oxygen leaving the material intact. So he melted the minerals which he alloyed with Mercury before passing a current.
The molten compound bubbled producing small clumps of a silvery metal on one electrode and liberating gaseous Oxygen on the other, the electrodes were inert so didn’t react with the electrolyte.
As well as Boron, Davy also discovered Aluminium Oxide (alumina), initially calling it Alumium then Aluminum, four years later, which the Americans followed, but the British disliked it as not following the ‘ium’ pattern of other elements, and so changed it.
Davy was instrumental in his use of electrolysis to separate compounds into elements, also found a way of reducing corrosion on copper-bottomed ships showing that chemical attraction may be exacted or modified or destroyed by a change in the electrical state of materials.
In Market Jew Street, Penzance there is a full-length marble statue to Sir Humphry Davy (1778-1829) sculpted by T. & W. Wills.
(1) Biography for Beginners (1905). E.C. Bentley’s, First Clerihew.
(2) On 2nd October 1798 Davy joined the Pneumatic Institution established for investigating the medical powers of ‘factitious air gases’ and after indifferent schooling and apprenticeship with an apothecary-surgeon at the Pneumatic Centre, Bristol. discovered nitrous oxide (N2O), laughing gas.
(3) Potassium was isolated from potash and is vital to agriculture as a fertilizer, comprising 93% of consumption owing to its quick depletion in intensive farming. Potassium also produces softer soaps.
(4) Sodium compounds are used in glass, metal, paper petroleum, pyrotechnics, soap, textiles, hard soaps and detergents.
Weeks, Mary Elvira (1933) XII The Discovery of the Elements Easton PA Journal of Chemical Education.