ISO 3073:1975 pdf download.Wool - Determination of acid content
1 SCOPE AND FIELD OF APPLICATION
ISO 3073:1975 pdf download specifics a method for determining the acid content of a wool sample, expressed as a percentagP 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 extracted during the test does not interfere with the determination of the end-point ot the titration.
2 PRINCIPLE
Immersion of a known amount of the wool in a dilute solution of pyridine which extracts the acid from the wool. Determination of the amount of acid extracted, by titration with standard sodium hydroxide solution.
3 REFERENCE
Iso 1130, Textile uibre — Soi,,e ,netlivds of soinpling for testing.
4 REAGENTS
4.1 Pyridine, 5 g/l 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 gIl ethanolic solution.
Dissolve 0,5 g ot phenolphthalein in Yb % (VIV) ethanol and dilute to 100 ml with the same ethanol.
5 APPARATUS
5.1 GIass-stoppered conical flasks, 250 ml capacity.
6 SAMPLING
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 PROCEDURE
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一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 100 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 (5.10), filtering through plugs of glass wool (5.11) 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 faint pink colour persists after a gentle shaking by hand.ISO 3073 pdf download.