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1.1 This test method covers the determination of chromic oxide in Wet Blue that has been partly or completely tanned with chromium compounds. In general, the samples will contain chromium content between 1 % and 5 % when calculated as chromic oxide expressed upon a dry basis otherwise referred to as moisture-free basis (mfb).
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This test method does not apply to Wet White.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. See Section 8 for specific safety hazards.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
5.1 The procedure described is specific for chromium in Wet Blue. Vanadium is the only common interfering element and is rarely present in quantity. Iron, when present from either water contamination or process chemicals, may also interfere by imparting a yellow color which could affect the endpoint of the titration. Phosphoric acid is added to complex any iron that may be present. For most commercially available wet blue, the iron content is not sufficient to cause an interference (see Table 1). Therefore, for most commercially available wet blue, the user may opt to exclude use of the phosphoric acid. Procedure Option B offers a method that uses a reduced sample size and less chemicals to obtain equivalent results (see Table 1).The precision and accuracy of the methods are usually, at least, as good as the sampling of Wet Blue itself.
5.2 The chromium content of Wet Blue is related to the degree of tannage obtained, and hence may be a matter for specification in the purchase of Wet Blue. The procedure described provides adequate accuracy for this purpose.
| SDO | ASTM: ASTM International |
| Document Number | D6656 |
| Publication Date | Dec. 1, 2024 |
| Language | en - English |
| Page Count | 5 |
| Revision Level | 24 |
| Supercedes | |
| Committee | D31.02 |
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