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Interaction Between Montmorillonite and Benzidine in Aqueous Solutions IV. The Color Reaction in the Frozen State
Author(s) -
Lahav N.,
Anderson D. M.
Publication year - 1973
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.197300049
Subject(s) - benzidine , chemistry , bentonite , aqueous solution , reflectivity , mineralogy , chemical engineering , organic chemistry , optics , physics , engineering
Abstract Changes in the color of Na, Ca, and Cu‐bentonite‐benzidine pastes were observed for color changes upon freezing at −5°C, −15°C, and −21°C. At −5°C no color change could be detected. At −15°C and −21°C, when the benzidine/bentonite ratio (W/W) was in the range of approximately 0.0003 to 0.003, the pastes' colors changed from blue or pale blue to green or bluish green. Reflectance measurements of Na‐bentonite‐benzedine paste at −150°C were carried out in a specially designed cell. These measurements show that in addition to the color change, the reflectivity of the frozen paste became higher upon freezing to −150°C, presumably because of the formation of ice crystals. The explanation of the color changes is based on the assumption that the (blue) monovalent and the (yellow) divalent cations coexist in the frozen paste at different zones on the bentonite surface.