a colloidal, hydrated aluminum silicate that swells 12 times its dry size when added to water. tsca definition 2008: a colloidal clay. consists primarily of montmorillonite. Used in foods as a colourant, pigment and stabiliser Also known as potash bentonite or K-bentonite, potassium bentonite is a potassium rich illitic clay formed from alteration of volcanic ash.; Bentonite is an absorbent aluminium phyllosilicate, generally impure clay consisting mostly of montmorillonite. There are a few types of bentonites and their names depend on the dominant elements, such as K, Na, Ca, and Al. As noted in several places in the geologic literature, there are some nomenclatorial problems with the classification of bentonite clays. Bentonite usually forms from weathering of volcanic ash, most often in the presence of water. However, the term bentonite, as well as a similar clay called tonstein, have been used for clay beds of uncertain origin. For industrial purposes, two main classes of bentonite exist: sodium and calcium bentonite. In stratigraphy and tephrochronology, completely devitrified (weathered volcanic glass) ash-fall beds are commonly referred to as K-bentonites when the dominant clay species is illite. Other common clay species, and sometimes dominant, are montmorillinite and kaolinite. Kaolinite dominated clays are commonly referred to as tonsteins and are typically associated with coal.; Bentoquatam protects the skin like a shield against poison ivy, poison oak, and poison sumac by physically blocking skin contact with their resin. The best protection against getting these conditions is to avoid contact with these plants. This medicine does not dry oozing and weeping caused by the rash of poison ivy, poison oak, or poison sumac.; Calcium bentonite is a useful adsorbent of ions in solution. as well as fats and oils, being a main active ingredient of Fuller's Earth, probably one of the earliest industrial cleaning agents. Calcium bentonite may be converted to sodium bentonite (termed sodium beneficiation or sodium activation) to exhibit many of sodium bentonite's properties by a process known as "ion exchange" (patented in 1935 by Germans U Hofmann and K Endell). Commonly this means adding 5-10% of a soluble sodium salt such as sodium carbonate to wet bentonite, mixing well, and allowing time for the ion exchange to take place and water to remove the exchanged calcium. Some properties, such as viscosity and fluid loss of suspensions, of sodium beneficiated calcium bentonite (or sodium activated bentonite) may not be fully equivalent to natural sodium bentonite. For example, residual calcium carbonates (formed if exchanged cations are insufficiently removed) may result in inferior performance of the bentonite in geosynthetic liners; Much of bentonite's usefulness in the drilling and geotechnical engineering industry comes from its unique rheological properties. Relatively small quantities of bentonite suspended in water form a viscous, shear thinning material. Most often, bentonite suspensions are also thixotropic, although rare cases of rheopectic behavior have also been reported. At high enough concentrations (~60 grams of bentonite per litre of suspension), bentonite suspensions begin to take on the characteristics of a gel (a fluid with a minimum yield strength required to make it move). For these reasons it is a common component of drilling mud used to curtail drilling fluid invasion by its propensity for aiding in the formation of mud cake.; Pascalite is a commercial name for the calcium bentonite clay.
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