ISO 939:2021 pdf download – Spices and condiments — Determination of moisture content.
6 Apparatus Distillation apparatus (a suitable form of apparatus is described in Annex A and shown in Figure A.1), comprising the following components fitted together by means of ground glass joints. 6.1 Flask, short-necked, of capacity at least 500 ml. 6.2? Reflux? condenser. 6.3 Receiver, with a graduated tube, interposed between the flask and the condenser. 6.4 Analytical balance. 7 Sampling Sample the material by the method specified in ISO 948. 8 Procedure 8.1 Preparation of apparatus Clean the entire apparatus with a laboratory-grade detergent to minimize the adherence of water droplets to the sides of the condenser and the receiver. Rinse thoroughly with water and dry completely before use. 8.2 Preparation of test sample Prepare the test sample by the method specified in ISO 2825. 8.3 Test portion Weigh, to the nearest 0,01 g, about 40 g of the test sample (see 8.2), such that the quantity of water collected will not exceed 4,5 ml.
8.4 Determination Transfer quantitatively the test portion (see 8.3) to the distillation flask (6.1), add sufficient toluene (5.1) (about 75 ml in all) to cover the sample completely and swirl to mix. Assemble the apparatus and fill the receiver (6.3) with the toluene by pouring it through the condenser (6.2) until it begins to overflow into the distillation flask. If necessary, insert a loose cotton plug in the top of the condenser or attach to it a small calcium chloride tube to prevent condensation of atmospheric moisture within the condenser tube. In order to control refluxing, wrap the flask and tube leading to the receiver with glass fibres, stone wool or ceramic fibres. Heat the flask so that the distillation rate is about 100 drops per minute. When the greater part of the water has distilled over, increase the distillation rate to about 200 drops per minute and continue until no more water is collected. Purge the reflux condenser occasionally during the distillation with 5 ml portions of the toluene to wash down any moisture adhering to the walls of the condenser. The water in the receiver may be made to separate from the toluene by occasionally moving a spiral copper wire up and down in the condenser and receiver, thus causing the water to settle at the bottom of the receiver. Reflux until the water level in the receiver remains unchanged for 30 min and then shut off the source of heat. Flush the condenser with toluene as required, making use of the spiral copper wire to discharge any moisture droplets. Immerse the receiver in water at room temperature for at least 45 min or until the toluene layer is clear. Then read the volume of water.