Bentonite, Form : Powder

Bentonite BP Ph Eur Grade Specifications
CAS 1302-78-9

DEFINITION
Natural clay containing a high proportion of montmorillonite, a native hydrated aluminium silicate in which some aluminium and silicon atoms may be replaced by other atoms such as magnesium and iron.

CHARACTERS
Appearance: Very fine, homogeneous, greyish-white powder with a more or less yellowish or pinkish tint.
Solubility: Practically insoluble in water and in aqueous solutions. It swells with a little water forming a malleable mass.

IDENTIFICATION
A. To 0.5 g in a metal crucible add 1 g of potassium nitrate and 3 g of sodium carbonate and heat until the mixture melts. Allow to cool. To this residue add 20 ml of boiling water, mix and filter. Wash the insoluble residue with 50 ml of water. To this residue add 1 ml of hydrochloric acid and 5 ml of water. Filter. To the filtrate add 1 ml of strong sodium hydroxide solution and filter. To this filtrate add 3 ml of ammonium chloride solution. A gelatinous white precipitate is formed.
B. Swelling power with water (see Tests).
C. 0.25 g gives the reaction of silicates.