ISO 3073:1975 pdf download – Wool- Determination of acid content

03-05-2022 comment

ISO 3073:1975 pdf download – Wool- Determination of acid content
This International Standard specifies a method for determining the acid content of a wool sample, expressed as a percentage by mass. This method is applicable to undyed wool in any form, for example loose fibre, sliver, yarn or fabric. It is also applicable to dyed wool when the amount of dye cxtracted during the test does not interfere with the determination of the end-point of the titration.
Immersion of a known amount of the wool in a dilute solution of pyridine which ex tracts the acid from the wool, Determination of the amount of acid extracted, by titration with standard sodium hydroxide solution.
ISO 1130, Textile fibres – Sorme methods of sampling for testing.
4.1 Pyridine, 5 g/1 solution.
Dissolve 5 g of pyridine (analytical grade) in 1 I of distilled water.
4.2 Sodium hydroxide, 0,1 N solution. .
Standardize this solution by titration with standard potassium hydrogen phthalate solution.
4.3 Phenolphthalein, 5 g/l ethanolic solution.
Dissolve 0,5g of phenolphthalein in 95 % (V/V) ethanol and dilute to 100 ml with the same ethanol.
5.1 Glass-stoppered conical flasks, 250 ml capacity.
Take a sample representative of the bulk and of mass not less than 10g1). It is assumed that the sample is commercially free from oil and fatty matter. Useful information on sampling is given in ISO 1130.
7.1 Take at least two test specimens representative of the sample, each of mass 2±0.001 g, and one specimen of mass 1±0,001 g.
7.2 Place the 1 g test specimen in a weighing bottle (5.5) and dry in the ventilated oven (5.8) at 105±3 °C. Stopper the bottle, cool in the desiccator (5.7) and determine the mass of the bottle and contents. Continue heating until constant mass2) has been attained. Remove the contents of the bottle and determine the dry mass of the specimen by determining the mass of the empty bottle. NOTE – Ensure that each specimen is treated in such a way that all have the same moisture content.
7.3 Place the other two test specimens in separate glass-stoppered conical flasks (5.1) and add 1 00 ml of pyridine Solution (4.1) to each. Stopper each flask and Shake on the mechanical shaker (5.9) for 1 h. Alternatively, allow each flask to stand overnight after initial shaking to ensure wetting of the specimen. Decant the liquid from each flask into separate glass beakers (5.1 0), filtering through plugs of glass wool (5.1 1 ) to retain fibrous material. From each beaker, pipette 50 ml of the filtered liquid into separate conical flasks (5.2), add 3 drops of phenolphthalein Solution (4.3) to each flask and titrate each extract with the sodium hydroxide Solution (4.2) until a f aint pink colour persists after a gentle shaking by hand. A potentiometric end-point determination is allowed.

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