BS 3584:1989 pdf free download.Method for Determination of solubility of wool in area-bisulphite solution.
1 Scope
BS 3584 describes a method for determination of the solubility of wool in urea-bisuiphite solution. This procedure is applicable to wool textiles in any form. i.e. loose fibre, silver, roving, yarn or fabric, but is not applicable if the specimen has been dyed with any metallized dye.
NOTE The titles of the publications referred to in BS 3584 are listed on the inside back cover.
2 Principle
A test specimen is immersed in a solution containing urea and disodium disuiphite (also known as sodium meta-bisuiphite) of known concentration and specified composition, under specified conditions of time, temperature and volume. The loss in mass is determined as the difference between the dry masses of the test specimen before and after treatment.
3 Reagents
NOTE All reagents should be of analytical reagent quality.
3.1 Urea-bisuiphite solution, freshly prepared on day of use, containing 50 g of urea, 3 g of disodium disulphite and 2 mL of 5 molIL sodium hydroxide per 100 mL.
Dissolve the urea in boiling water, add the disodium disulphite, cool, add 2 mL sodium hydroxide solution and make-up to volume. Check the pH value using a glass electrode pH meter and adjust to 7.0 ± 0.1 if necessary.
3.2 Urea solution, containing 25 g urea per 100 mL. Dissolve 250 g urea in 1 000 mL of water.
3.3 Water, complying with grade 3 of BS 3978.
3.4 Petroleum spirit, boiling range 40 00 to 60 °C.
4 Apparatus
41 Soxhiet extraction apparatus complying with
BS 2071.
4.2 Water bath, or other means for controlling the temperature of the flask and contents
at 65 ± 0,50 °C.
4.3 C’onical flasks, 250 mL capacity, fitted with stoppers.
4.4 Sintered -glass filter crucibles, :io mL capacity, of porosity P 160 in accordance with BS 1752.
NOTE If possible, these crucibles should have ground glass stoppers
4.5 Filter-flask, filter-pump and adaptor
4.6 Ventilated oven, for drying specimens at 105 ± 30 °C.
4.7 Stoppered weighing bottles
4.8 Balance, accurate to ± 0.0002 g
4.9 Desiccator.
5 Test specimens
Take a sample representative of the bulk and not less than 10 g sufficient to provide wool for the following test specimens:
a) one test specimen weighing approximately 1 g for determining the dry mass (see 6.2);
b) two test specimens each weighing approximately 1 g for determining the solubility in urea-bisuiphite (see 6.3).
NOTE 1 If it is suspected that the sample contains acid (see 6.4) two further test specimens each weighing approximately 2 g may be taken from the sample for determining acid content by the method described in BS 6981.
NOTE 2 Useful information on sampling is given in BS 2545. NOTE 3 The precision of results may be quite high given a very uniform sample, but, for example, in testing dyed loose wool the variations within the batch could be ± 2 % or more and fresh test specimens may be needed.
6 Procedure
6.1 Preparation of sample
Extract the sample in the Soxhiet extraction apparatus (4.1) using petroleum spirit (3.4) for 1 h at a minimum rate of six cycles per hour. Allow the petroleum spirit to evaporate and then remove all vegetable and other obvious foreign matter. Disintegrate the sample into short lengths of approximately 10 mm and allow them to come to equilibrium with the laboratory atmosphere.
6.2 Determination of dry mass
Place the 1 g test specimen (see clause 5) in a weighing bottle (4.7) and dry it in the ventilated oven (4.6) at 105 ± 3 °C. Stopper the bottle, cool it in the desiccator (4.9) and weigh it. Repeat these drying, cooling and weighing operations until the results of two consecutive weighings do not differ from each other by more than 0.0005 g, i.e. the mass is virtually constant.
Remove the test specimen. weigh the weighing bottle and hence calculate the dry mass of the test specimen.
6.3 Determination of solubility in urea-bisuiphite
Measure 100 mL portions of the urea-bisuiphite solution (3.1) into separate flasks (4.3), stopper loosely, and fix the flasks in the water-bath (4.2) by any suitable means so that the level of the water outside the flasks is at least 50 mm higher than the level of the solution inside.
NOTE This procedure is essential for precise control of temperature.
When the temperature of the urea-bisuiphite solution reaches 65 ± 0.5 °C, introduce separate test specimens of known mass (see clause 5) into the flasks, replace the stoppers and gently shake the flasks to ensure complete wetting of the test specimens. Shake the flasks gently again after 15, 30 and 45 mm, the time of shaking not to exceed 5 s on each occasion.
After 1 h transfer the contents of each flask to separate sintered-glass filter crucibles (4.4) of known mass and drain the crucibles by suction. Wash any fibrous material remaining in each flask into the crucibles with urea solution (10 mL each time) (3.2). Wash each residue in each crucible six times with water (3.3). Allow the liquid to stand in contact with the residue for about 15 s before draining completely after each wash, and release the suction.
Dry the crucibles and contents at 105 ± 3°C for not less than 3 h and not more than 16 h, cool them in the desiccator and weigh them.
Repeat these drying, cooling and weighing operations until the results of two consecutive weighings do not differ from each other by more than 0.0005 g, i.e. the mass is virtually constant.
6.4 Determination of acid content Determine the pH value of the aqueous extract by the cold water method described in BS 3266. If an aqueous extract of the material has a pH value less than 4.0, determine the acid content by the method described in BS 6981.
7 Expression of results
7.1 Samples not containing acid
The solubility of urea-bisuiphite. S. calculated as the loss in mass of the test specimen and expressed as a percentage of its calculated dry mass, is given by the equation:
m1 is the dry mass of the test specimen determined as described in 6.2 (in g);
m is the dry mass of the residue determined as described in 6.3 (in g).
7.2 Samples containing acid
The corrected solubility in urea-bisuiphite, S’, calculated as the loss in mass of the test specimen expressed as a percentage of its calculated dry, acid-free mass is given by the equation:
where
S is the uncorrected solubility in
urea-bisuiphite (calculated as
described in 7.1):
s is the percentage of acid determined as described in BS 6981.
Express the results to one decimal place.
8 Test report
The test report shall include the following information:
a) the number and date of this British Standard,
i.e. BS 3584:1989;
b) a description or reference of the sample tested;
c) the individual results and their mean, as
expressed in clause 7;
d) any departure from the method described,
e.g. owing to insufficient material being
available.