Growth into a Scientific Discipline: The Nineteenth Century - Important Figures of Analytical Chemistry from Germany in Brief Biographies - page 71

of mineralogy, geology and mining at the School of Polytechnics Delft, where
he founded the first microchemical laboratory (1897). In 1898, he was appointed
Professor of microchemistry at Amsterdam.
With his publications Mikrochemische Methoden zur Mineral - Analyse
(Microchemical methods of the analysis of minerals) and Beiträge zur mik-
rochemischen Analyse—Methoden und Reaktionen der einzelnen Elemente
(Contributions to microchemical analysis—methods and reactions of the single
elements) as well as with several editions of the two volumes Anleitung zur mikro-
chemischen Analyse 1894 and 1895-1898, he is regarded as one of the founders of
microchemical analysis [ 198 ].
Alexander C lassen (born 13 April 1843, Aachen; died 28 January 1934, Aachen)
Classen studied from 1861 at the universities Giessen and Berlin, where he
graduated with a PhD and worked as assistant in Berlin for two years. Based in his
private laboratory in Aachen (established in 1866), he gave lectures on analytical
chemistry, became Dozent (Lecturer) in 1870 and Professor for organic and analyt-
ical chemistry (1878/1882) and was Director of the Institute of Electrochemistry of
the Königlich Rheinisch-Westphälische Polytechnische Schule (Technical College,
now Rheinisch-Westfälische Technische Hochschule/RWTH) Aachen until 1914.
In 1923, he became honorary doctor of the RWTH Aachen.
Classen is one of the founders of electrochemical analysis [ 199 ] with his stud-
ies on the influences of voltage and current density on the deposition of metals,
and he e.g., recognized the advantages of higher temperatures and of stirring, and
recommended in 1897 express methods with rotating anode [ 200 ]. His institute
became internationally known as a centre of electrochemistry.
He described the formation of sugar and alcohol from cellulose [ 201 ] and pub-
lished (together with Roscoe) a textbook on inorganic and analytical chemistry, a
handbook, selected methods, quantitative electrochemical analysis, and volumetric
analysis [ 202 - 204 ]. Classen was also editor of the last issue of Mohr's textbook on
titrimetry in 1914 [ 32 ].
Walther H empel (born 5 May 1851, Pulsnitz/Saxony; died 1 December 1916,
Dresden)
Hempel studied from 1867 at the Königlich Sächsische Polytechnische Schule
(Royal Polytechnic, now Technische Universität) Dresden, 1871/1872 at the
Friedrich-Wilhelms-Universität Berlin (at August Wilhelm von Hofmann and
Adolf von Baeyer), and 1872 in Heidelberg (Robert Bunsen), where he gradu-
ated with a PhD. In 1873, he went to Dresden ( Zentralstelle für öffentliche
Gesundheitspflege, , Center for Public Health) and became soon assistant of Schmitt
at the Chemical Laboratory of the Polytechnic, where he habilitated in 1878 and
was appointed Extraordinary Professor in 1879. In 1880, he became Professor for
Technical Chemistry, and in 1893, he became Professor for inorganic experimental
chemistry and for inorganic technical chemistry (both until 1912). He was Rector
of the Polytechnic 1902-1903.
He invented several instruments (Hempel pipette, Hempel burette, a calorimet-
ric bomb for the estimation of combustion heat, and Hempel oven for volumetry