ISO 1833-18-2020 pdf download.Textiles一Quantitative chemical analysis – Part 18: Mixtures of silk with wool or other animal hair (method using sulfuric acid).
5.1 Sulfuric acid, with a mass fraction of 75 %.
While cooling, carefully add 700 ml of concentrated sulfuric acid (p = 1,84 g/ml at 20 °C) to 350 ml of water. After cooling this solution to room temperature, dilute it to 11 with water. The concentration is not critical within the range of a mass fraction of 73 % to 77% sulfuric acid.
5.2 Sulfuric acid, dilute solution.
Slowly add 100 ml of concentrated sulfuric acid (p = 1,84 g/ml at 20°C) to 1 900 ml of water.
5.3 Ammonia, dilute solution.
Dilute 200 ml of concentrated ammonia solution (p = 0,88 g/ml at 20°C) to II with water.
6 Apparatus
Use the apparatus described in ISO 1833-1 together with that given in &1.
6.1 Conical flasks, of minimum capacity 200 ml, glass stoppered.
7 Test procedure
Follow the general procedure described in ISO 1833-1, and then proceed as follows.
Add 100 ml of the sulfuric acid (5.1) per gram of specimen to the specimen contained in a glassstoppered conical flask. Insert the stopper, shake vigorously (preferably in a mechanical shaker) and allow to stand for 30 mm at room temperature.
Shake again and allow to stand for 30 mm.
Shake a last time and filter the contents of the flask through the weighed filter crucible. Wash any remaining fibres from the flask with a little sulfuric acid (5.1).
Drain the crucible using suction and wash the residue on the crucible successively with 50 ml of the dilute sulfuric acid solution (&Z), 50 ml of water and 50 ml of the dilute ammonia solution (5.3). Each time, allow the fibres to remain in contact with the liquid for at least 10 mm before applying suction.
Rinse with water, leaving the fibres in contact with the water for about 30 mm.
Finally, drain the crucible using suction, dry the crucible and residue, then cool and weigh them.
8 Calculation and expression of results
Calculate the results as described in the general instructions of ISO 1833-1.
The value of d is 0,985.
9 Precision
On a homogeneous mixture of textile materials, the confidence limits of results obtained by this method are not greater than ±1 percentage point for a confidence level of 95 %.ISO 1833-18 pdf download.