Council Directive of 26 February 1973 on the approximation of the laws of the Member States relating to the quantitative analysis of ternary fibre mixtures (73/44/EEC) (repealed)

ANNEX I QUANTITATIVE ANALYSIS OF TERNARY FIBRE MIXTURES

GENERAL

Introduction

Methods for the quantitative analysis of fibre mixtures are based on two processes, the manual separation and the chemical separation of fibre types.

The method of manual separation should be used whenever possible since it generally gives more accurate results than the chemical method. It can be used for all textiles whose component fibres do not form an intimate mixture, as for example in the case of yarns composed of several elements each of which is made up of only one type of fibre or fabrics in which the warp is of a different type of fibre from the weft; or knitted fabrics capable of being unravelled made up of yarns of different types.

In general, the methods of quantitative chemical analysis are based on the selective solution of the individual components. There are four possible variants of this method:

1.

Using two different test specimens, a component (a) is dissolved from the first test specimen, and another component (b) from the second test specimen. The insoluble residues of each specimen are weighed and the percentage of each of the two soluble components is calculated from the respective losses in mass. The percentage of the third component (c) is calculated by difference.

2.

Using two different test specimens, a component (a) is dissolved from the first test specimen and two components (a and b) from the second test specimen. The insoluble residue of the first test specimen is weighed and the percentage of the component (a) is calculated from the loss in mass. The insoluble residue of the second test specimen is weighed; it corresponds to component (c). The percentage of the third component (b) is calculated by difference.

3.

Using two different test specimens, two components (a and b) are dissolved from the first test specimen and two components (b and c) from the second test specimen. The insoluble residues correspond to the two components (c) and (a) respectively. The percentage of the third component (b) is calculated by difference.

4.

Using only one test specimen, after removal of one of the components, the insoluble residue formed by the two other fibres is weighed and the percentage of the soluble component is calculated from the loss in mass. One of the two fibres of the residue is dissolved, the insoluble component is weighed and the percentage of the second soluble component is calculated from the loss in mass.

Where a choice is possible, it is advisable to use one of the first three variants.

Where chemical analysis is used, the expert responsible for the analysis must take care to select methods employing solvents which dissolve only the correct fibre(s), leaving the other fibre(s) intact.

By way of example, a table is given in Annex III which contains a certain number of ternary mixtures, together with methods for analysing binary mixtures which can, in principle, be used for analysing these ternary mixtures.

In order to reduce the possibility of error to a minimum, it is recommended that, whenever possible, chemical analysis using at least two of the four abovementioned variants should be made.

Mixtures of fibres used during processing and, to a lesser extent, in finished textiles may contain non-fibrous matter, such as fats, waxes or dressings, or water-soluble matter, either occurring naturally or added to facilitate processing. Non-fibrous matter must be removed before analysis. For this reason a method of pre-treatment for removing oils, fats, waxes and water-soluble matter is also given.

In addition, textiles may contain resins or other matter added to confer special properties. Such matter, including dyestuffs in exceptional cases, may interfere with the action of the reagent on the soluble components and/or it may be partially or completely removed by the reagents. This type of added matter may thus cause errors and should be removed before the sample is analysed. If it is impossible to remove such added matter the methods for quantitative chemical analysis given in Annex III attached are no longer applicable.

Dye in dyed fibres is considered to be an integral part of the fibre and is not removed.

Analyses are conducted on the basis of dry mass and a procedure is given for determining dry mass.

The result is obtained by applying to the dry mass of each fibre the recovery rates listed in Annex II to the Directive on the approximation of the laws of the Member States relating to textile names.

Before proceeding with any analysis, all the fibres present in the mixture must be identified. In some chemical methods, the insoluble component of a mixture may be partially dissolved in the reagent used to dissolve the soluble component(s). Wherever possible, reagents have been chosen that have little or no effect on the insoluble fibres. If a loss in mass is known to occur during the analysis, the result should be corrected; correction factors are given for this purpose. These factors have been determined in several laboratories by treating, with the appropriate reagent as specified in the method of analysis, fibres cleaned by the pre-treatment. These correction factors apply only to undergraded fibres and different correction factors may be necessary if the fibres have been degraded before or during processing. If the fourth variant, in which a textile fibre is subjected to the successive action of two different solvents, must be used, correction factors must be applied for possible losses in mass undergone by the fibre in the two treatments. At least two determinations should be made, both in the case of manual separation and in the case of chemical separation.

I. GENERAL INFORMATION ON METHODS FOR THE QUANTITATIVE CHEMICAL ANALYSIS OF TERNARY FIBRE MIXTURES

Information common to the methods given for the quantitative chemical analysis of ternary fibre mixtures.

I.1. Scope and field of application

The field of application of each method for analysing binary fibre mixtures specifies to which fibres the method is applicable. (See Annex II, Directive relating to certain methods for the quantitative analysis of binary fibre mixtures).

I.2. Principle

After the identification of the components of a mixture, the non-fibrous material is removed by suitable pre-treatment and then one or more of the four variants of the process of selective solution described in the introduction is applied. Except where this presents technical difficulties, it is preferable to dissolve the major fibre component so as to obtain the minor fibre component as final residue.

I.3. Apparatus and Reagents

I.3.1. Apparatus

I.3.1.1. Filter crucibles and weighing bottles large enough to contain such crucibles, or any other apparatus giving identical results.

I.3.1.2. Vacuum flask.

I.3.1.3. Desiccator containing self-indicating silica gel.

I.3.1.4. Ventilated oven for drying specimens at 105 ± 3 ^oC.

I.3.1.5. Analytical balance, accurate to 0-0002 g.

I.3.1.6. Soxhlet extractor or other apparatus giving identical results.

I.3.2. Reagents

I.3.2.1. Light petroleum, redistilled, boiling range 40 to 60 ^oC.

I.3.2.2. Other reagents are specified in the appropriate parts of the text of the method. All reagents used should be chemically pure.

I.3.2.3. Distilled or deionized water.

I.4. Conditioning and testing atmosphere

Because dry masses are determined, it is unnecessary to condition the specimens or to conduct analyses in a conditioned atmosphere.

I.5. Laboratory test sample

Take a laboratory test sample that is representative of the laboratory bulk sample and sufficient to provide all the specimens, each of at least 1 g, that are required.

I.6. Pre-treatment of the laboratory test sample

Where a substance not to be taken into account in the percentage calculations (See Article 12 (2) (d) of the Directive relating to textile names) is present, it should first be removed by a suitable method that does not affect any of the component fibres.

For this purpose, non-fibrous matter which can be extracted with light petroleum and water is removed by treating the air-dry test sample in a Soxhlet extract selector with light petroleum for one hour at a minimum rate of 6 cycles per hour. Allow the light petroleum to evaporate from the sample which is then directly extracted with water by soaking for one hour at room temperature followed by soaking at 65 ± 5 ^oC for a further one hour, agitating the liquid from time to time, specimen/water ratio 1: 100. Remove the excess water from the sample by squeezing, suction, or centrifuging and then allow the sample to become air-dry.

Where non-fibrous matter cannot be extracted with light petroleum and water, it should be removed by substituting for the water method described above a suitable method that does not substantially alter any of the fibre constituents. However for some unbleached natural vegetable fibres (eg jute, coir) it is to be noted that normal pre-treatment with light petroleum and water does not remove all the natural non-fibrous substances; nevertheless additional pre-treatment is not applied unless the sample contains finishes insoluble in both light petroleum and water.

Analytical reports should include full details of the methods of pre-treatment used.

I.7. Test procedure

I.7.1. General instructions

I.7.1.1. Drying

Conduct all drying operations for not less than 4 hours and not more than 16 hours at 105 ± 3 ^oC in a ventilated oven with the oven door closed throughout. If the drying period is less than 14 hours, the specimen must be checkweighed to determine whether its mass is constant. The mass may be considered as constant if, after a further drying period of 60 minutes, its variation is less than 005 %.

Avoid handling crucibles and weighing bottles, specimens or residues with bare hands during the drying, cooling and weighing operations.

Dry specimens in a weighing bottle with its cover beside it. After drying, stopper the weighing bottle before removing it from the oven, and transfer it quickly to the desiccator.

Dry the filter crucible in a weighing bottle with its cover beside it in the oven. After drying, close the weighing bottle and transfer it quickly to the desiccator.

Where apparatus other than a filter crucible is used, drying operations should be conducted in the oven so as to determine the dry mass of the fibres without loss.

I.7.1.2. Cooling

Conduct all cooling operations in the desiccator, placed beside the balance, until the cooling of the weighing bottles is complete, and in any case for not less than 2 hours.

I.7.1.3. Weighing

After cooling, complete the weighing of the weighing bottle within 2 minutes of its removal from the desiccator; weigh to an accuracy of 00002 g.

I.7.2. Procedure

Take from the pre-treated laboratory test sample a test specimen of at least 1 g (in mass). Cut yarn or cloth into lengths of about 10 mm, dissected as much as possible. Dry the specimen(s) in (a) weighing bottle(s) cool it (them) in the desiccator and weigh it (them). Transfer the specimen(s) to the glass vessel(s) specified in the appropriate section of the Community method, reweigh the weighing bottle(s) immediately and obtain the dry mass(es) of the specimen(s) by difference; complete the test as specified in the appropriate section of the applicable method. Examine the residue(s) microscopically to check that the treatment has in fact completely removed the soluble fibre(s).

I.8. Calculation and expression of results

Express the mass of each component as a percentage of the total mass of fibre in the mixture. Calculate the results on the basis of clean dry mass, adjusted by (a) the conventional recovery rates and (b) the correction factors necessary to take account of loss of non-fibrous matter during pre-treatment and analysis.

I.8.1. Calculation of percentages of mass of clean dry fibres disregarding loss of fibre mass during pre-treatment.

I.8.1.1. — VARIANT 1 —

Formulae to be applied where a component of the mixture is removed from one specimen and another component from a second specimen:

P₃% = 100 — (P₁% + P₂%);

P₁%

is the percentage of the first clean dry component (component in the first specimen dissolved in the first reagent);

P₂%

is the percentage of the second clean dry component (component in the second specimen dissolved in the second reagent);

P₃%

is the percentage of the third clean dry component (component undissolved in both specimens);

m₁

is the dry mass of the first specimen after pre-treatment;

m₂

is the dry mass of the second specimen after pre-treatment;

r₁

is the dry mass of the residue after removal of the first component from the first specimen in the first reagent;

r₂

is the dry mass of the residue after removal of the second component from the second specimen in the second reagent;

d₁

is the correction factor for loss in mass in the first reagent, of the second component undissolved in the first specimen(1);

d₂

is the correction factor for loss in mass in the first reagent of the third component undissolved in the first specimen(1);

d₃

is the correction factor for loss in mass in the second reagent, of the first component undissolved in the second specimen(1);

d₄

is the correction factor for loss in mass in the second reagent, of the third component undissolved in the second specimen(1).

I.8.1.2. — VARIANT 2 —

Formulae to be applied where a component (a) is removed from the first test specimen, leaving as residue the other two components (b + c), and two components (a + b) are removed from the second test specimen, leaving as residue the third component (c):

P₁% = 100 — (P₂% + P₃%)

P₁%

is the percentage of the first clean dry component (component of the first specimen soluble in the first reagent);

P₂%

is the percentage of the second clean dry component (component soluble, at the same time as the first component of the second specimen, in the second reagent);

P₃%

is the percentage of the third clean dry component (component insoluble in both specimens);

m₁

is the dry mass of the first specimen after pre-treatment; m₂ is the dry mass of the second specimen after pre-treatment;

r₁

is the dry mass of the residue after removal of the first component from the first specimen in the first reagent;

r₂

is the dry mass of the residue after removal of the first and second components from the second specimen in the second reagent;

d₁

is the correction factor for loss in mass in the first reagent, of the second component undissolved in the first specimen(2);

d₂

is the correction factor for loss in mass in the first reagent, of the third component undissolved in the first specimen(2);

d₄

is the correction factor for loss in mass in the second reagent, of the third component undissolved in the second specimen(2).

I.8.1.3. — VARIANT 3 —

Formulae to be applied where two components (a + b) are removed from a specimen, leaving as residue the third component (c), then two components (b + c) are removed from another specimen, leaving as residue the first component (a):

P₁

% is the percentage of the first clean dry component (component dissolved by the reagent);

P₂

% is the percentage of the second clean dry component (component dissolved by the reagent);

P₃

% is the percentage of the third clean dry component (component dissolved in the second specimen by the reagent);

m₁

is the dry mass of the first specimen after pre-treatment; m₂ is the dry mass of the second specimen after pre-treatment;

r₁

is the dry mass of the residue after removal of the first and second components from the first specimen with the first reagent;

r₂

is the dry mass of the residue after removal of the second and third components from the second specimen with the second reagent;

d₂

is the correction factor for loss in mass with the first reagent of the third component undissolved in the first specimen(2);

d₃

is the correction factor for loss in mass with the second reagent of the first component undissolved in the second specimen(3).

I.8.1.4. — VARIANT 4 —

Formulae to be applied where two components are successively removed from the mixture using the same specimen:

P₁% = 100 — (P₂% + P₃%)

P₁%

is the percentage of the first clean dry component (first soluble component);

P₂%

is the percentage of the second clean dry component (second soluble component);

P₃%

is the percentage of the third clean dry component (insoluble component);

m

is the dry mass of the specimen after pre-treatment;

r₁

is the dry mass of the residue after elimination of the first component by the first reagent;

r₂

is the dry mass of the residue after elimination of the first and second components by the first and second reagents;

d₁

is the correction factor for loss in mass of the second component in the first reagent(3);

d₂

is the correction factor for loss in mass of the third component in the first reagent(3);

d₃

is the correction factor for loss in mass of the third component in the first and second reagents(4).

I.8.2. Calculation of the percentage of each component with adjustment by conventional recovery rates and, where appropriate, correction factors for losses in mass during pre-treatment operations:

Given:

then

P₁A%

is the percentage of the first clean dry component, including moisture content and loss in mass during pre-treatment;

P₂A%

is the percentage of the second clean dry component, including moisture content and loss in mass during pre-treatment;

P₃A%

is the percentage of the third clean dry component, including moisture content and loss in mass during pre-treatment;

P₁

is the percentage of the first clean dry component obtained by one of the formulae given in I.8.1;

P₂

is the percentage of the second clean dry component obtained by one of the formulae given in I.8.1;

P₃

is the percentage of the third clean dry component obtained by one of the formulae given in I.8.1;

a₁

is the conventional recovery rate of the first component;

a₂

is the conventional recovery rate of the second component;

a₃

is the conventional recovery rate of the third component;

b₁

is the percentage of loss in mass of the first component during pre-treatment;

b₂

is the percentage of loss in mass of the second component during pre-treatment;

b₃

is the percentage of loss in mass of the third component during pre-treatment.

Where a special pre-treatment is used the values b₁, b₂ and b₃ should be determined, if possible, by submitting each of the pure fibre constituents to the pre-treatment applied in the analysis. Pure fibres are those free from all non-fibrous material except those which they normally contain (either naturally or because of the manufacturing process), in the state (unbleached, bleached) in which they are found in the material to be analysed.

Where no clean separate constituent fibres used in the manufacture of the material to be analysed are available, average values of b₁, b₂ and b₃ as obtained from tests performed on clean fibres similar to those in the mixture under examination, must be used.

If normal pre-treatment by extraction with light petroleum and water is applied, correction factors b₁, b₂ and b₃ may generally be ignored, except in the case of unbleached cotton, unbleached flax and unbleached hemp where the loss due to pre-treatment is usually accepted as 4 % and in the case of polypropylene as 1 %.

In the case of other fibres, losses due to pre-treatment are usually disregarded in calculations.

I.8.3. Note

Calculation examples are given in Annex II to this Directive.

II. METHOD OF QUANTITATIVE ANALYSIS BY MANUAL SEPARATION OF TERNARY FIBRE MIXTURES

II.1. Scope

This method is applicable to textile fibres of all types provided they do not form an intimate mixture and that it is possible to separate them by hand.

II.2. Principle

After identification of the textile components, the non-fibrous matter is removed by a suitable pre-treatment and then the fibres are separated by hand, dried and weighed in order to calculate the proportion of each fibre in the mixture.

II.3. Apparatus

II.3.1. Weighing bottles or other apparatus giving identical results.

II.3.2. Desiccator containing self-indicating silica gel.

II.3.3. Ventilated oven for drying specimens at 105 ± 3 ^oC.

II.3.4. Analytical balance accurate to 0.0002 g.

II.3.5. Soxhlet extractor, or other apparatus giving identical results.

II.3.6. Needle.

II.3.7. Twist tester or similar apparatus.

II.4. Reagents

II.4.1. Light petroleum, redistilled, boiling range 40^o—60 ^oC.

II.4.2. Distilled or deionized water.

II.5. Conditioning and testing atmosphere.

See I.4.

II.6. Laboratory test sample

See I.5.

II.7. Pre-treatment of laboratory test samples

See I.6.

II.8. Procedure

II.8.1. Analysis of yarn

Take from the pre-treated laboratory test sample a specimen of mass not less than 1 g. For a very fine yarn, the analysis may be made on a minimum length of 30 m, whatever its mass.

Cut the yarn into pieces of a suitable length and separate the fibre types by means of a needle and, if necessary, a twist tester. The fibre types so obtained are placed in pre-weighed weighing bottles and dried at 105 ± 3 ^oC to constant mass, as described in I.7.1 and I.7.2.

II.8.2. Analysis of cloth

Take from the pre-treated laboratory test sample a specimen of mass not less than 1 g, not including a selvedge with edges carefully trimmed to avoid fraying and running parallel with weft or warp yarns, or in the case of knitted fabrics in the line of the wales and courses. Separate the different types of fibres and collect them in pre-weighed weighing bottles and proceed as described in II.8.1.

II.9. Calculation and expression of results

Express the mass of each component fibre as a percentage of the total mass of the fibres in the mixture. Calculate the results on the basis of clean dry mass, adjusted by (a) the conventional recovery rates and (b) the correction factors necessary to take account of losses in mass during pre-treatment operations.

II.9.1. Calculation of percentage masses of clean dry fibre, disregarding loss in fibre mass during pre-treatment:

P₃% = 100 — (P₁% + P₂%);

P₁%

is the percentage of the first clean dry component;

P₂%

is the percentage of the second clean dry component;

P₃%

is the percentage of the third clean dry component;

m₁

is the clean dry mass of the first component;

m₂

is the clean dry mass of the second component;

m₃

is the clean dry mass of the third component.

II.9.2. For calculation of the percentage of each component with adjustment by conventional recovery rates and, where appropriate, by correction factors for losses in mass during pre-treatment: see I.8.2.

III. METHOD OF QUANTITATIVE ANALYSIS OF TERNARY FIBRE MIXTURES BY A COMBINATION OF MANUAL SEPARATION AND CHEMICAL SEPARATION

Wherever possible, manual separation should be used, taking account of the proportions of components separated before proceeding to any chemical treatment of each of the separate components.

IV. PRECISION OF THE METHODS

The precision indicated in each method of analysis of binary mixtures relates to the reproducibility (see Annex II of the Directive relating to certain methods for the quantitative analysis of binary textile fibre mixtures).

Reproducibility refers to the reliability, ie the closeness of agreement between experimental values obtained by operators in different laboratories or at different times using the same method and obtaining individual results on specimens of an identical homogeneous mixture.

Reproducibility is expressed by confidence limits of the results for a confidence level of 95%.

By this is meant that the difference between two results in a series of analyses made in different laboratories would, given a normal and correct application of the method to an identical and homogeneous mixture, be exceeded only in 5 cases out of 100.

To determine the precision of the analysis of a ternary mixture the values indicated in the methods for the analysis of binary mixtures which have been used to analyse the ternary mixture are applied in the usual way.

Given that in the four variants of the quantitative chemical analysis of ternary mixtures, provision is made for two dissolutions (using two separate specimens for the first three variants and a single specimen for the fourth variant) and, assuming that E₁ and E₂ denote the precision of the two methods for analysing binary mixtures, the precision of the results for each component is shown in the following table:

VariantsComponent fibre	1	2 and 3	4
a	E1	E1	E1
b	E2	E1 + E2	E1 + E2
c	E1 + E2	E2	E1 + E2

If the fourth variant is used, the degree of precision may be found to be lower than that calculated by the method indicated above, owing to possible action of the first reagent on the residue consisting of components b and c, which would be difficult to evaluate.

V. TEST REPORT

V.1. Indicate the variant(s) used to carry out the analysis, the methods, reagents and correction factors.

V.2. Give details of any special pre-treatments (See I.6).

V.3. Give the individual results and the arithmetic mean, each to the 1st decimal place.

V.4. Wherever possible, state the precision of the method for each component, calculated according to the table in section IV.

(1)

The values of d are indicated in the corresponding sections of the Directives relating to the various methods of analysing binary mixtures.

(2)

The values of d are indicated in the corresponding sections of the Directives relating to the various methods of analysing binary mixtures.

(3)

The values of d are indicated in the corresponding sections of the Directives relating to the various methods of analysing binary mixtures.

(4)

Wherever possible d₃ should be determined in advance by experimental methods.