the condenser known as the liebig type, a most basic circulating fluid-cooled design, was invented by several investigators working independently; however, the earliest laboratory condenser was invented in 1771 by the swedish-german chemist christian weigel (1748–1831). weigel’s condenser consisted of two coaxial tin tubes, which were joined at their lower ends and open at their upper ends. cold water entered, via an inlet, the lower end of this jacket and spilled out of the jacket’s open upper end. a glass tube carrying vapors from a distillation flask passed through the inner tin tube, not in contact with the cooling water. weigel subsequently replaced the inner tin tube with a glass tube, and he devised a clamp to hold the condenser. in 1791, the german chemist johann friedrich august göttling (1753–1809), who was a former student of weigel, sealed both ends of weigel's condenser. the german chemist justus liebig (1803–1873) eliminated the inner wall of weigel’s condenser, placing, in direct contact with the jacket’s cooling water, the glass tube carrying vapors from the distillation flask. he also replaced, with glass, the outer metal wall of weigel’s condenser. and he used rubber hoses, instead of metal tubes, to convey water to and from the condenser.