Action and use: Antidiarrhoeal.
DEFINITION
Light Kaolin is a native hydrated aluminium silicate, freed from most of its impurities by elutriation and dried. It contains a suitable dispersing agent.
CHARACTERISTICS
A light, white powder free from gritty particles; odourless or almost odourless; unctuous. Practically insoluble in water and in mineral acids.
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 the residue add 20 ml of boiling water, mix and filter. Wash the residue with 50 ml of water, add to the residue 1 ml of hydrochloric acid and 5 ml of water, mix and filter. To the filtrate add 1 ml of strong sodium hydroxide solution, filter and add to the filtrate 3 ml of ammonium chloride solution. A gelatinous white precipitate is produced.
B. 0.25 g yields the reaction characteristic of silicates.
C. Triturate 2 g with 2 ml of water. The resulting mixture flows.
TESTS
Coarse particles: Transfer 5 g to a stoppered cylinder (about 16 cm × 35 mm), add 60 ml of a 1% w/v solution of sodium pyrophosphate, shake thoroughly and allow to stand for 5 minutes. Using a pipette, withdraw 50 ml from a point about 5 cm below the surface of the liquid. To the remaining liquid add 50 ml of water, shake, allow to stand for 5 minutes and withdraw 50 ml in the same manner as before. Repeat the operation until a total of 400 ml of suspension has been withdrawn under the prescribed conditions. Transfer the remainder to an evaporating dish and evaporate to dryness on a water bath. The residue, after drying at 105C, weighs not more than 25 mg.
Fine particles: Disperse 5 g in 250 ml of water by shaking vigorously for 2 minutes in a stoppered flask, pour immediately into a glass cylinder 5 cm in diameter and transfer 20 ml to a glass dish using a pipette. Evaporate to dryness and dry to constant weight at 105C. Allow the remainder of the suspension to stand for 4 hours at 20C and withdraw a second 20 ml portion using a pipette with its tip exactly 5 cm below the surface and without disturbing the sediment. Transfer the second portion to a glass dish, evaporate to dryness and dry to constant weight at 105C. The weight of the residue from the second portion is not less than 70% of the weight of the residue from the first portion.
Arsenic: 0.50 g dispersed in 25 ml of water complies with the limit test for arsenic, (2 ppm).
Heavy metals: To pass the test
Chloride: Boil 1.0 g with 80 ml of water and 20 ml of 2M nitric acid under a reflux condenser for 5 minutes, cool and filter. 15 ml of the filtrate complies with the limit test for chlorides, (330 ppm).
Loss on drying: When dried to constant weight at 105C, loses not more than 1.5% of its weight. Use 1 g.
Loss on ignition: When ignited at 600C, loses not more than 15.0% of its weight. Use 1 g.
Soluble matter: Boil 2 g with 100 ml of 0.2M hydrochloric acid under a reflux condenser for 5 minutes, cool, filter and evaporate 50 ml of the filtrate to dryness. The residue, after ignition at about 600C for 30 minutes, weighs not more than 10 mg.
Ph Eur
DEFINITION
Purified, natural, hydrated aluminium silicate of variable composition.
CHARACTERS
Appearance: Fine, white or greyish-white, unctuous powder.
Solubility: Practically insoluble in water and in organic solvents.
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 the residue add 20 ml of boiling water, mix and filter. Wash the residue with 50 ml of water. To the 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 the filtrate add 3 ml of ammonium chloride solution. A gelatinous white precipitate is formed.
B. 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 greater than 5 ml.
C. 0.25 g gives the reaction of silicates.
TESTS
Solution S: To 4 g add a mixture of 6 ml of acetic acid and 34 ml of distilled water, shake for 1 min and filter.
Acidity or alkalinity: To 1.0 g add 20 ml of carbon dioxide-free water, shake for 2 min and filter. To 10 ml of the filtrate add 0.1 ml of PhPh solution. The solution is colourless. Not more than 0.25 ml of 0.01 M sodium hydroxide is required to change the colour of the indicator to pink.
Organic impurities: Heat 0.3 g to redness in a calcination tube. The residue is only slightly more coloured than the original substance.
Adsorption power: To 1.0 g in a ground-glass-stoppered test-tube add 10.0 ml of a 3.7 g/l solution of methylene blue and shake for 2 min. Allow to settle. Centrifuge and dilute the solution 1 to 100 with water. The solution is not more intensely coloured than a 0.03 g/l solution of methylene blue.
Swelling power: Triturate 2 g with 2 ml of water. The mixture does not flow.
Substances soluble in mineral acids: Maximum 1 per cent.
Chlorides: Maximum 250 ppm.
Sulphates: Maximum 0.1 per cent.
Calcium: Maximum 250 ppm.
Heavy metals: Maximum 50 ppm.
Microbial contamination: Total viable aerobic count (2.6.12) not more than 1000 micro-organisms per gram, determined by plate-count.
LABELLING
The label states, where applicable, that the substance is suitable for internal use.
Action and use: Antidiarrhoeal.
DEFINITION
Light Kaolin (Natural) is a native hydrated aluminium silicate, freed from most of its impurities by elutriation and dried. It does not contain a dispersing agent.
CHARACTERISTICS
A light, white powder free from gritty particles; odourless or almost odourless; unctuous. Practically insoluble in water and in mineral acids.
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 the residue add 20 ml of boiling water, mix and filter. Wash the residue with 50 ml of water, add to the residue 1 ml of hydrochloric acid and 5 ml of water, mix and filter. To the filtrate add 1 ml of strong sodium hydroxide solution, filter and add to the filtrate 3 ml of ammonium chloride solution. A gelatinous white precipitate is produced.
B. 0.25 g yields the reaction characteristic of silicates.
C. Triturate 2 g with 2 ml of water. The resulting mixture does not flow.
TESTS
Coarse particles; Arsenic; Heavy metals; Chloride; Loss on drying; Loss on ignition; Soluble matter: Complies with the requirements stated under Light Kaolin.
Fine particles: Disperse 5 g in 250 ml of water containing 50 mg of sodium pyrophosphate by shaking vigorously for 2 minutes in a stoppered flask, pour immediately into a glass cylinder 5 cm in diameter and transfer 20 ml to a glass dish using a pipette. Evaporate to dryness and dry to constant weight at 105C. Allow the remainder of the suspension to stand for 4 hours at 20C and withdraw a second 20 ml portion using a pipette with its tip exactly 5 cm below the surface and without disturbing the sediment. Transfer the second portion to a glass dish, evaporate to dryness and dry to constant weight at 105C. The weight of the residue from the second portion is not less than 70% of the weight of the residue from the first portion.
Kaolin is a native hydrated aluminum silicate, powdered and freed from gritty particles by elutriation.
Identification: Mix 1 g with 10 mL of water and 5 mL of sulfuric acid in a porcelain dish. Evaporate the mixture until the excess water is removed, and continue heating the residue until dense, white fumes of sulfur trioxide appear. Cool, cautiously add 20 mL of water, boil for a few minutes, and filter: there remains on the filter a gray residue (impure silica). The filtrate responds to the tests for Aluminum.
Microbial limits: It meets the requirements of the test for absence of Escherichia coli.
Loss on ignition: Ignite between 550 and 600C: it loses not more than 15.0% of its weight.
Acid-soluble substances: Digest 1.0 g with 20 mL of 3 N hydrochloric acid for 15 minutes, and filter: 10 mL of the filtrate, evaporated to dryness and ignited, leaves not more than 10 mg of residue (2.0%).
Carbonate: Mix 1.0 g with 10 mL of water and 5 mL of sulfuric acid: no effervescence occurs.
Iron: Triturate 2.0 g in a mortar with 10 mL of water, and add 0.50 g of sodium salicylate: the mixture does not acquire more than a slight reddish tint.
Lead: To 1.0 g contained in a centrifuge tube add 10 mL of 1 N nitric acid, and digest for 1 hour in a boiling water bath. Centrifuge until the solids are completely separated, and pour the supernatant into a 100-mL volumetric flask. Add 5 mL of 1 N nitric acid to the Kaolin, mix, and digest for 15 minutes in a boiling water bath. Centrifuge, and add the supernatant to the previous extract in the volumetric flask. Dilute with water to volume. A 50-mL portion of this solution contains not more than 5 microgm of lead (corresponding to not more than 0.001% of Pb) when tested as directed in the test for Lead 251, using 3 mL of Ammonium Citrate Solution, 1 mL of Potassium Cyanide Solution, and 500 microL of Hydroxylamine Hydrochloride Solution.
We also offer Light Kaolin IP
Kaolin FCC Food Grade
China Clay
CAS: [1332-58-7]
DESCRIPTION
Kaolin occurs as a fine, white to yellow-white or gray powder that becomes darker when moistened. It is a purified clay consisting mainly of alumina, silica, and water. It is insoluble in water, in alcohol, in dilute acids, and in alkali solutions.
Function: Anti-caking agent.
