Test Method D 2462 for testing for moisture in wool is considered satisfactory for acceptance testing of commercial shipments since current estimates of between-laboratory precision are acceptable.
In case of a dispute arising from differences in reported test results when using Test Method D 2462 for acceptance testing of commercial shipments, the purchaser and the supplier should conduct comparative testing to determine if there is a statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of the bias. As a minimum, the two parties should take a group of test specimens that are as homogenous as possible and that are from a lot of the type material in question. The test specimens should be assigned in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using Student''s t-Test for unpaired data and an acceptance probability level chosen by the two parties before the test is begun. If a bias is found, either its cause must be found and corrected or the purchaser and the supplier must agree to interpret future test results in light of the known bias.
This test method is the preferred method for all suitable samples of wool where it is important to obtain a result free from the possible biases, introduced by the conditions discussed in 5.3 and 5.4.
This test method is free from the interferences caused by different conditions of ambient atmosphere such as might affect the results of oven-drying. A slight amount of residual moisture may be retained in a specimen subjected to oven-drying because of the relative humidity of the ambient air; however, the amount of moisture retained may be estimated from published data.
This test method is free from the interference caused by nonaqueous volatile material. Such material, when present, is erroneously measured as moisture by oven-drying methods, the extent of the error depending upon the amount and characteristics of any added oils or finishes.
This test method is relatively cumbersome, time consuming, and costly compared to oven-drying, and is not recommended for routine process control, in-plant evaluations, or for other purposes where a high degree of accuracy is not necessary. The cost of operation can be reduced somewhat by redistilling the used toluene, which is then suitable for reuse without further treatment.
Unlike an oven-drying method, any moisture gained or lost by a specimen after its mass has been determined will appear as a direct error in the final result. Since one of the principal uses of the method is to determine the average moisture present in large lots of wool or wool products exposed to variable atmospheric conditions, numerous laboratory samples and test specimens are common. To avoid errors of the type mentioned above, this procedure includes provisions for stabilizing the sample(s) in the laboratory atmosphere so that, during the time necessary for selecting, weighing, and transferring the specimens to flasks, gain or loss of moisture which cannot be accounted for will be minimized. A further advantage of the stabilizing process is realized in cases where the interest is solely in the average moisture content of the sample, and the actual moisture content within the sample is highly variable. By stabilizing the sample before selecting the specimens, equal precision can be achieved with fewer specimens.
1.1 This test method covers the determination of the amount of moisture present in grease wool, scoured wool, carded wool, garnetted wool, wool top and intermediate wool products, and rovings, by distillation with toluene.
1.2 Equations are given for calculating the amount of water present as moisture content (as-received basis) and moisture regain (dry fiber) basis. The term that corresponds to the basis used in the calculati......
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