Clays and Clay Minerals

, Volume 19, Issue 6, pp 383–390 | Cite as

Mechanisms of Formation of Colored Clay-Organic Complexes. A Review

  • B. K. G. Theng


The interactions of clay minerals with organic compounds which give rise to the formation of colored complexes, are discussed. The color reactions of clays can be ascribed to a charge transfer between the mineral and the adsorbed species. The active sites on the clay are aluminums exposed at crystal edges and/or transition metal cations in the higher valency state at planar surfaces both of which can act as electron acceptors. The pH of the system, the nature of the solvent and that of the exchangeable cation, influence the rate of color development and the final intensity and quality of the color produced. Steric factors also play a part in reactions involving bulky organics. Some practical applications based on color reactions of clays with electron-donating organic substances are described.


Les interactions des minéraux argileux avec les composés organiques qui donnent naissance à la formation de complexes colorés sont discutées. Les réactions colorées avec les argiles peuvent être attribuées à un transfert de charge entre le minéral et l’espèce adsorbée. Les sites actifs de l’argile sont les atomes d’aluminium exposés sur les bords des cristaux, et/ou, les cations métalliques de transition dans un état de valence élevée sur les surfaces basales, chacun d’eux pouvant agir comme accepteur d’électrons. Le pH du système, la nature du solvant et celle du cation échangeable, influencent la vitesse du développement de la coloration, et l’intensité et la qualité finales de la teinte produite. Des facteurs stériques jouent également un rôle dans les réactions se produisant avec les composés organiques encombrants. Un certain nombre d’applications pratiques fondées sur les réactions colorées des argiles avec les composés organiques donneurs d’électrons sont décrites.


Die gegenseitige Einwirkung von Tonmineralen und organischen Verbindungen, die zur Bildung farbiger Komplexe führen kann, wird erörtert. Die Farbreaktionen der Tone kann einem Ladungsübergang zwischen Mineral und adsorbiertem Stoff zugeschrieben werden. Die Aktivstellen am Ton sind exponiertes Aluminium an den Kristallkanten und/oder Übergangsmetallkationen in der höheren Valenzstufe an ebenen Flächen, welche beide als Elektronenakzeptoren wirksam sein können. Das pH des Systems, die Art des Lösungsmittels und die des austauschfähigen Kations beeinflussen die Geschwindigkeit der Farbentwicklung und die schliessliche Stärke und Qualität der erzeugten Farbe. Sterische Faktoren spielen gleichfalls eine Rolle bei Reaktionen mit umfangreicheren organischen Stoffen. Es werden einige praktische Anwendungen auf Grund von Farbreaktionen von Tonen mit elektronenabgebenden organischen Stoffen angeführt.


Обсуждается характер взаимодействия глинистых минералов с органическими соединениями, которое приводит к образованию окрашенных комплексов. Цветная реакция глин может быть приписана перемещению заряда между минералом и адсорбированным веществом. Активными центрами на поверхности глины являются атомы алюминия, выходящие на грани кристаллов и/или катионы переходных металлов в высоко валентном состоянии на плоских поверхностях; оба типа центров могут вести себя как акцепторы электронов. На скорость появления окраски, ее конечную интенсивность и характер влияют рН системы, природа растворителя и обменных катионов. Стерические факторы также играют роль при реакциях с объемными органическими молекулами. Описаны некоторые примеры практического применения методики, основанного на цветных реакциях глин с злектронно-донорными органическими соединениями.


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Copyright information

© The Clay Minerals Society 1971

Authors and Affiliations

  • B. K. G. Theng
    • 1
  1. 1.Soil Bureau, D.S.I.R.Lower HuttNew Zealand

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