ClearOFF BentoniteS™ Natural Sodium Bentonite Clay Powder - Montmorillonite, Hydrated Aluminosilicate (1600g)

Description

1600g of BentoniteS (sodium bentonite powder). Bentonites are hydrated aluminosilicate minerals, comprised chiefly of montmorillonite. Structurally they consist of alumina sheets sandwiched between tetrahedral SiO4 units. Water is usually present between the triple layers. A simplified formula for montmorillonite is: (OH)2Al2Si4O10 or Al2O3.4SiO2.H2O In reality, a proportion of the Al3+ are replaced by Mg2+ and Fe3+ (the plates are therefore positively charged at their edges and negatively charged at their surfaces). Wherever a Mg2+ occurs, the charge imbalance is compensated for by the presence of exchangeable cations – predominantly sodium or calcium, though minor amounts of several other metals will also be present. As a result, bentonites typically exhibit a cation exchange capacity (CEC) of 70 – 100 meq/gram. When bentonite is mixed with water, the water molecules will enter between the clay plates, forcing them apart. While the plates are dispersed, the bentonite slurry becomes quite fluid. However, on standing the particles become oriented with the negative surfaces of the plates being attracted to the positive edges. Viscosity increases and a gel is formed – a reversible effect known as thixotropy. A typical empirical formula for bentonite is: (Al, Fe0.67 Mg0.33) Si4O10(OH)2Na,Ca0.33