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Determining Completion of Excess Salt Removal from Clays: Method Comparisons
Author(s) -
Mekonnen Eyasu J.,
Nater Edward A.,
Laird David A.
Publication year - 1993
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1993.03615995005700030039x
Subject(s) - bentonite , salt (chemistry) , sonication , chemistry , mixing (physics) , conductivity , mineralogy , analytical chemistry (journal) , extraction (chemistry) , nuclear chemistry , chromatography , geology , organic chemistry , paleontology , physics , quantum mechanics
Abstract Three methods of determining the extent of excess salt removal during alcohol washing of clays were compared. Clays (<2 µm) separated from Wyoming bentonite, halloysite, and a Fargo soil (fine, montmorillonitic, frigid Vertic Haplaquoll) were saturated with 0.5 M CaCl 2 or 1.0 M KCl. Excess salts were removed by eight consecutive washes with 95% ethanol. Vortex and ultrasonication mixing methods were also compared. After centrifugation, the supernatants were analyzed for excess salt by (i) the AgNO 3 ‐Cl test, and by measuring (ii) electrical conductivity, and (iii) elemental concentrations. Elemental concentration and conductivity measurements indicated that substantial amounts of excess Ca and K (approximately 5 to 10% of CEC) remained in the clays when the AgNO 3 ‐Cl test was first negative. Ultrasonication reduced the number of washings required to remove excess salt from clays when compared with vortex mixing. The results demonstrate that electrical conductivity is a rapid and reliable method of determining completion of excess salt removal.