Bentonite

Bentonite BP
Ph Eur 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.

TESTS
Alkalinity: To 2 g add 100 ml of carbon dioxide-free water and shake for 5 min. To 5 ml of this suspension add 0.1 ml of thymolphthalein solution. The liquid becomes bluish. Add 0.1 ml of 0.1 M hydrochloric acid . The liquid is decolourised within 5 min.
Coarse particles: Maximum 0.5 per cent.
To 20 g add 1000 ml of water and mix for 15 min using a high-speed mixer capable of operating at not less than 5000 r/min. Transfer the suspension to a wet sieve (75), tared after drying at 100-105C. Wash with 3 quantities, each of 500 ml, of water, ensuring that any agglomerates have been dispersed. Dry the sieve at 100-105C and weigh. The particles on the sieve weigh a maximum of 0.1 g.
Sedimentation volume: To 6.0 g add 200 ml of water and mix for 20 min using a high-speed mixer capable of operating at 10000 r/min. Transfer 100 ml of this suspension to a graduated cylinder. Allow to stand for 24 h. The volume of the clear supernatant liquid is not greater than 2 ml.
Swelling power with water: Add 2.0 g in 20 portions to 100 ml of a 10 g/l solution of sodium laurilsulfate in a 100 ml graduated cylinder about 30 mm in diameter. Allow 2 min between additions for each portion to settle. Allow to stand for 2 h. The apparent volume of the sediment is not less than 22 ml.
Heavy metals: Maximum 50 ppm.
Loss on drying: Maximum 15 per cent, determined on 1.000 g by drying in an oven at 105C.
Microbial contamination: Total viable aerobic count not more than 103 micro-organisms per gram, determined by plate-count.

Bentonite USP NF
Bentonite [1302-78-9].
Bentonite is a native, colloidal, hydrated aluminum silicate.

Identification: Add 2 g in small portions to 100 mL of water, with intense agitation. Allow to stand for 12 hours to ensure complete hydration. Place 2 mL of the mixture so obtained on a suitable glass slide, and allow to air-dry at room temperature to produce an oriented film. Place the slide in a vacuum desiccator over a free surface of ethylene glycol. Evacuate the desiccator, and close the stopcock so that the ethylene glycol saturates the desiccator chamber. Allow to stand for 12 hours. Record the Xray diffraction pattern, and calculate the d values: the largest peak corresponds to a d value between 15.0 and 17.2 angstrom units. Prepare a random powder specimen of Bentonite, record the X-ray diffraction pattern, and determine the d values in the region between 1.48 and 1.54 angstrom units: the peak is between 1.492 and 1.504 angstrom units.
Microbial limits: It meets the requirements of the test for absence of Escherichia coli.
pH: Disperse 4.0 g in 200 mL of water, mixing vigorously to facilitate wetting. The pH of this suspension is between 9.5 and 10.5.
Loss on drying: Dry it at 105C for 2 hours: it loses between 5.0% and 8.0% of its weight.
Arsenic: limit is 5 ppm.
Lead: (0.004%).
Gel formation: Mix 6 g with 300 mg of magnesium oxide. Add the mixture, in several divided portions, to 200 mL of water contained in a blender of approximately 500-mL capacity. Blend thoroughly for 5 minutes at high speed, transfer 100 mL of the mixture to a 100-mL graduated cylinder, and allow to remain undisturbed for 24 hours: not more than 2 mL of supernatant appears on the surface.
Swelling power: To 100 mL of water contained in a glass-stoppered cylinder of 100-mL capacity add 2 g in portions, dropping it upon the surface of the water and allowing each portion to settle before adding the next. The mass at the bottom gradually swells until it occupies an apparent volume of not less than 24 mL at the end of a 2-hour period.
Fineness of powder: Sprinkle 2 g upon 20 mL of water contained in a mortar. Allow to swell, disperse evenly with a pestle, and dilute with water to 100 mL. Pour the suspension through a No. 200 standard sieve, and wash the sieve thoroughly with water. No grit is felt when the fingers are rubbed over the wire mesh of the sieve.

Certifications :
We manufacture Bulk Drugs / API, Excipients, Pharmaceuticals (IP/BP/USP/NF/Ph. Eur, JP/ CP), Speciality Chemicals(Pure/AR/ACS), Mineral Fortifiers, Food Chemical Codex (FCC) and Flavour chemicals. Our manufacturing facility is cGMP, GLP, ISO 9001, ISO 14001, ISO 22000, ISO/IEC 17025, FSSC 22000, FSSAI, Kosher, HALAL, EXCiPACT, WC, COPP, WHO-GMP and WC certified. We are also REACH registered for export to European countries.