Important Figures in Analytical Chemistry from Germany: From the Middle Ages to the Nineteenth Century - Important Figures of Analytical Chemistry from Germany in Brief Biographies - page 25

Fig. 2.9 Portrait of Johann
Heinrich Lambert
(ca. 1728-1777)
Lambert's topic, Photometria [ 95 ], that deals with optical measurements was
published in 1760. In it, he stated:
If a light beam with an intensity I passes through a layer [in his experiments, of glass]
of width l , its intensity will decrease to I 1/n of its original intensity while if it passes
through a further similar layer its intensity will decrease to I 1/n 1/n of its original
value. For m layers the intensity of the exiting light will be I ′ = I/n m .
He also noted:
The amount of captured light is the greater, the greater the number of particles within a
given volume and the larger the surface area of a given particle.
Later, in 1852, Beer pointed out that the Lambert law also applied to solutions and
defined the absorption coefficient [ 96 ].
The Beer-Lambert law could equally be described as the Bouguer-Bernard
law. Bouguer's research predated but was unknown to Lambert, his Essai [ 97 ] was
published in 1729. Bernard also defined the absorption coefficient, a few months
after Beer [ 98 ].
The Demise of Phlogiston and the Rise of Stoichiometry
and Quantitation
Carl Wilhelm S cheele (born 19 December 1742, Stralsund; died 21 May 1786,
Köping, Sweden) is normally listed as a Swedish chemist but is included herein
because Stralsund is in Western Pomerania, then a Province of Prussia, although