purple of Cassius

…He first studied in Vienna, then organic chemistry at the University of Munich, and after working as an assistant to physicist AA Kundt in Berlin and a private lecturer at the Technical University of Graz, he joined the Schott glass company in Jena, and later became a professor at the University of Göttingen (1907-27). At the glass company, he researched colored and opaque glass, and invented the famous Jenaer Glas (trade name). During this time, he became interested in colloids due to the similarity between red gold colloidal solutions and ruby-colored glass, and studied gold colloidal solutions, showing that the "purple of Cassius," which had long been used to color glass surfaces, was a mixture of fine gold particles and stannic acid (1898). He invented a device for observing colloidal solutions under a microscope by shining light on them from the side (1900), and improved it with HFW Siedentopf to invent the ultramicroscope (1903), which made it clear that colloidal solutions were heterogeneous suspensions in which the theory of molecular motion was valid. …

*Some of the terminology that mentions "purple of Cassius" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…最初ウィーンに学び，ミュンヘン大学で有機化学を学び，ベルリンで物理学者クントA.A.Kundtの助手，グラーツの工業大学私講師を経て，イェーナのショットSchott･ガラス会社に入ったのち，ゲッティンゲン大学教授(1907‐27)。ガラス会社で色ガラスや不透明ガラスを研究し，有名なエナガラスJenaer Glas(商品名)を発明したが，その間に金の赤色コロイド溶液とルビー色ガラスの類似からコロイドに興味をもち，金のコロイド溶液を研究し，ガラス表面を着色するために古くから用いられた〈カシウス紫purple of Cassius〉が細かい金の粒子とスズ酸の混合物であることを示した(1898)。コロイド溶液の側面から光をあて顕微鏡で見る装置をくふうし(1900)，ジーデントップH.F.W.Siedentopfとともにそれを改良し限外顕微鏡を発明(1903)，コロイド溶液が分子運動論の成立する不均一系懸濁液であることが明確になった。…

※「purple of Cassius」について言及している用語解説の一部を掲載しています。

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