ISO 2916:1975 pdf download – Wool – Determination of alkali content

03-05-2022 comment

ISO 2916:1975 pdf download – Wool – Determination of alkali content
1 SCOPE AND FIELD OF APPLICATION
This International Standard specifies a method for the determination of the alkali content of wool. The method is applicable to undyed wool in any form; for example, loose fibres, card sliver, tops, yarn or fabric. It can be used with dyed wool if the amount of dye extracted in the course of the test does not affect the determination of the end-point of the titration.
2 PRINCIPLE
Extraction of the alkali from a weighed quantity of wool by immersion in dilute boric acid solution. Determination of the amount of alkali extracted, by titration with a standard volumetric solution of hydrochloric acid.
5 SAMPLING AND PREPA RATION OF TEST SPECIMENS
Take a representative sample of mass not less than 10 g from the material to be tested. If the dichloromethane extract of the sample is greater than 1 %, degrease with dichloromethane as follows : Extract the sample with dichloromethane for 1 h in a Soxhlet apparatus, at the minimum rate of 6 cycles per hour. Evaporate the dichloromethane from the cleaned sample and remove all vegetable matter and foreign substances from the wool. If the sample is yarn or cloth, dissect into short lengths of yarn (approximately 1 cm) and leave to attain equilibrium with the laboratory atmosphere. Felted materials that cannot be dissected into yarn must first be cut up into small pieces.
Stopper the bottle, allow it to cool in the desiccator (4.8), remove and determine its mass. Repeat these drying and mass determination operations until constant mass has been attained. 1) . Remove the test specimen, determine the mass of the weighing bottle and hence determine the dry mass of the test specimen. Calculate by proportion the dry mass of the other test specimens.
6.2 Determination of alkali content
Place each of the other test specimens in a conical flask (4.1) and add by pipette (4.4) 100 ml of boric acid solution (3.1). Stopper the flasks and either shake for 2 h on the mechanical shaker (4.10) or allow to stand overnight after first shaking by hand to wet out the wool. Decant the liquid from the wool and filter through the sinteredglass crucible (4.6) in order to remove fibre fragments. Transfer by pipette <4.4) 50 ml of the filtered liquid to an Erlenmeyer flask (4.2) and titrate with the N/20 hydrochloric acid solution (3.2), using 3 drops of methyi red and 3 drops of methylene blue solutions (3.3) as indicator.
An interlaboratory trial was carried out by a Working Group using three wools of different alkali contents. Nine laboratories participated. The statistical evaluation of the resulting 3X 9 X 2 values (each laboratory carried out a double test on each wool) produced the values summarized in the following table.

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