Udagawa Yōan

nihongo|Udagawa Yōan|宇田川 榕菴|extra = 1798 – 1846 was a 19th-century Japanese scholar of Western Studies, or "Rangaku". In 1840, he published his nihongo|"Introduction to Chemistry"|舎密開宗|Seimi Kaisō, a compilation of various scientific books in Dutch, which describes a wide range of scientific knowledge from the West. Most of the Dutch original material appears to be derived from William Henry's 1799 "Elements of Experimental Chemistry". In particular, the book contains a very detailed description of the electric battery invented by Volta forty years earlier in 1800. The battery itself was constructed by Utagawa in 1831, and used in various experiments, including medical ones, based on a belief that electricity could help cure illnesses.

Utagawa's "Science of Chemistry" also reports for the first time in details the findings and theories of Lavoisier in Japan. Accordingly Utagawa also made numerous scientific experiments, and created new scientific terms, which are still in current use in modern scientific Japanese; e.g. nihongo|“oxidation”|酸化|sanka, nihongo|“reduction”|還元|kangen, nihongo|“saturation”|飽和|hōwa, and nihongo|“element”|元素|genso.