hydrolyzed formaldehyde. The approp

hydrolyzed formaldehyde. The appropriate test should be chosen based on that distinction. 13.2 A simple cloth support for insertion in the mason jars can be constructed as follows:A piece of aluminum wire screening 15.2 x14.0 cm (6.0 x 5.5 in.) is bent around a length of wood 3.8 cm (1.5 in.) square and fastenedtogether to form a rectangular, open-ended cage. One side is cut at the corners about half-way up the side and the cut section folded in-ward and fastened. This folded piece forms the bottom of the wire basket while the other three sides form the support legs. Fasteningcan be accomplished场twisting short lengths of wire through or around the appropriate part.The wire screening should not be a source of formaldehyde. Test before using. 13.3 The ratio of reagent to sample soludons can be adjusted, within limits, to suit the individual absorbance range and optical pathlength of the sampling tubes or cuvettes of the particular photometric instrument being used.For example, although 5 mL reagent to 5 mL sample solution has been found convenient for several types of instruments, other 1:1 ratios,such as a ratio of 2 mL reagent to 2 mL sample may be more suitable for others. The same ratio should be used with the standards as withthe sample. The use of spectrophotometer tubes directly for color developments avoids the transfer step, test tubes to spectrophotome-ter cells, and may save considerable time when many determinations are to be made.Repipettes or similar devices can be used for reagent dispensing, and disposable tip automatic pipettes can be used for the sample solupons. 13.4 The procedure in Section 10 has been set up to cover the range from about 0 dug/g on the weight of the fabric to about 500 dug/g. In fabrics containing releasable formaldehyde in the range from 500 dug/g on the weight of the fabric to about 3500 dug/g, it is recommended that a ratio of 10-mL Nash reagent to 1 mL sample be used. If this is done, it is necessary to prepare an additional calibration chart with 10:1 ratios of standard solutions to Nash reagent by diluting 5.0, 10.0, 15.0 and 20.0 wg/mL, respectively, of the approximately 1500 dug/mL standardized stock solution of formalde场de to the mark with deionized water in 500-mL volumetric flasks. Formalde场de solutions containing approximately 15, 30, 45 and 60 dug/ mL respectively will be obtained (see 8.3). 13.5 The chromotropic acid colorimetric method can be used as an alternate to the Nash reagent for the determination of the formalde-场de content of the sample jars after oven incubation. It should be noted that the Precision and Bias Statement was not developed usingthe chromotropic acid method. A suitable procedure is given in J. Frederick Walker, Formaide场de, 3rd Edition, Reinhold PublishingCo., N丫1964,酬70. When using this method, a change may be necessary in the size of both the aliquots taken from the sample jars(see 10.2) and the standard formaldehyde solutions used in preparing the calibration curve(see 8.3). CAUTION: Since concentrated sulfuric acid is used with the chromotropic acid method, adequate care should be exercised to protect operating personnel and spectrophotometric eqmpment. 13.6 Incubation conditions of 65士10C (149士40F) for 4 h can be used as an alternate to the incubation conditions of 49士10C (120