Pure potassium was first isolated in 1807 in England by Humphry Davy, who derived it from caustic potash (KOH, potassium hydroxide) by the use of electrolysis of the molten salt with the newly invented voltaic pile.
pjˈʊɹ pətˈæsiəm wʌz fˈɜːst ˈaɪsəlˌeɪɾᵻd ɪn wˈʌn θˈaʊzənd ˈeɪthˈʌndɹɪd sˈɛvən ɪn ˈɪŋɡlənd baɪ hˈʌmfɹi dˈeɪvi, hˌuː dᵻɹˈaɪvd ɪt fɹʌm kˈɔːstɪk pˈɑːɾæʃ kˌeɪˌoʊˈeɪtʃ, pətˈæsiəm haɪdɹˈɑːksaɪd baɪ ðə jˈuːs ʌv ᵻlɛktɹˈɑːləsˌɪs ʌvðə mˈoʊltən sˈɔlt wɪððə nˈuːli ɪnvˈɛntᵻd voʊltˈeɪɪk pˈaɪl.