1. Joannes Beguinus,Tyrocinium Chymicum, commentario illustratum a Gerardo Blasio, 2nd ed. Amsterdam (1669), p. 2, with the editor's footnote: "Cum experientia practicae veritatem theoriae corroboret, unice verum Chymiatriae studiosum eo allaborandum esse censemus, ut manuali experientiae noctu diuque incumbat, quo tandem dulcissima hujus artis usura frui possit".
2. Previously Hermann Boerhaave,Sermo academicus de chemia suos errores expurgante, Leiden, 1718, p. 12 and also [Gabriel François Venel]Chymie, in: Encyclopedic ou dictionnaire raisonné des sciences, des arts et des métiers, Tome I (Paris 1751), pp. 435–436. For further reference compare also Jost Weyer,Chemiegeschichtsschreibung von Wiegleb(179o)bis Partington(1970). (Arbor Scientiazum, Reihe A, 3) Hildesheim, 1974, while the Marxist interpretation of the history of chemistry would keep to the dogmatic-systematic separation of theory and practice, as does Wilhelm Strube,Die Chemieundihre Geschichte(Forschungen zur Wirtschaftsgeschichte, 5) Berlin, 1974, andidem, Der historische Weg der Chemie, Vol. I-II, Leipzig, 1976–198/.