5.1 Qualitative and quantitative fiber identification is actively pursued by committee RA24 (Fiber Identification) of AATCC and presented in AATCC Test Methods 20 and 20A. Since precision and bias development is also part of the AATCC test methods, both AATCC and ASTM D13 have agreed that new development will take place in RA24. However, because there is valuable information still present in the ASTM standards, D13.51 has agreed Test MethodsD276 and D629 will be maintained as active standards by ASTM.

5.2 Test Methods D629 for the determination of quantitative analysis of textiles may be used for acceptance testing of commercial shipments but caution is advised since information on between-laboratory precision is lacking. Comparative tests as directed in 5.2.1 or in Standard Tables D1909 may be advisable.

5.2.1 In case of a dispute arising from differences in reported test results using Test Methods D629 for acceptance testing of commercial shipments, the purchaser and the supplier should conduct comparative tests to determine if there is a statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. As a minimum, the two parties should take a group of test specimens which are as homogeneous as possible and which are from a lot of material of the type in question. The test specimen should then be randomly assigned in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using Student's t-test and an acceptable probability level chosen by the two parties before the testing began. If a bias is found, either its cause must be found and corrected or the purchaser and supplier must agree to interpret future test results in the light of the known bias.

5.3 The effects of the various reagents used in the chemical methods on the residual fibers in a blend depend upon the history of the fibers and, unless otherwise stated, are generally too small or too uncertain to warrant the application of correction factors.

5.4 Fiber composition is generally expressed either on the oven-dry mass of the original sample or the oven-dry mass of the clean fiber after the removal of nonfibrous materials. If nonfibrous materials are not first removed from the textile before the fiber analysis is carried out, or if the treatments described in Section 8 are incapable of removing them, any such materials present will increase the percentage of the fiber constituent with which they are removed during the analysis, assuming they are soluble in the solvent used.

5.5 The analytical methods are intended primarily for the separation of binary mixtures of fibers. These procedures may also be used for the analysis of mixtures containing more than two types of fibers by selecting the best combination of methods to use (Table 1). Since a sequence of solvents on a given fiber may produce different results than the expected results from a single solvent, it is advisable to determine the results of such sequential effects when testing multiple fiber blends. It is sometimes more convenient to separate mechanically the yarns in a textile which are of similar types, and then use the appropriate chemical method to analyze each of the components. Table 2 shows the solubilities of the various fibers in different chemical reagents.

(A) Key to Methods and Reagents:

Method No. 1-80 % acetone(cold)

Method No. 2- N-Butyrolactone

Method No. 3-90 % formic acid

Method No. 4-59.5 % sulfuric acid

Method No. 5-70 % sulfuric acid

Method No. 6-Sodium hypochlorite solution

Method No. 7-Curpammonia solution

Method No. 8-Hot xylene

Method No. 9-90 % formic acid

Method No. 10-N,N-dimethylacetamide

(B) Each analytical method is identified by a number and where possible, two methods of analysis are provided for each binary mixture of fibers. The number or numbers inside parentheses refers to the method that dissolves the fiber shown at the top of the diagram. The number or numbers outside the parentheses indicates the method that dissolves the fiber listed at the left side of the diagram. Where two methods are listed for a specific binary mixture, the non-superscript method number represents the method of choice. (A) Key to Symbols:

S  =  Soluble

PS  =  Partially Soluble

SS  =  Slightly Soluble (a correction factor may be applied)

I  =  Insoluble

(B) Reworked wools are soluble in 70 % H₂SO₄ depending upon their previous history.