ISO 2916:1975 pdf download.Wool - Determination of alkali content
1 SCOPE AND FIELD OF APPL ICATION
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 extr acted 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.
3.1 Boric acid solution.
Dissolve 10 g of boric acid (analytical reagent grade) in 1 I of distilled water.
3.2 Hydrochloric acid, N/20 solution.
Standardize this solution by titration with freshly standardized sodium hydroxide solution.
3.3 MethyI red - Methylene blue indicator :
a) A 1 g/1 solution of methyI red in absolute ethanol.
b) 4ml of a 10 g/l aqueous solution of methylene blue mixed with 96 mi of ethanol with warming.
5 SAMPLING AND PREPARATION 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 1h 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.
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 sintered-glass 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.
Carry out a titration on each extract and obtain the mean volume of N/20 hydrochloric acid solution used in the two titrations.ISO 2916 pdf download.