DIN EN ISO 17489:2014-03

The traditional method for analysing the tanning component in a tanning agent uses chromium (III) tanned hide powder and measures the proportion of tanning agent that is adsorbed onto the hide powder. The non-adsorbable fraction, consisting largely of inorganic salts, remains in the tanning solution. By determining the dry content of the initial tanning solution and the non-adsorbable fraction, the adsorbable fraction can be easily calculated - this is the tanning component in the tanning agent. The traditional hide powder method is a recognised method to determine the tanning strength of tanning agents. However, for reproducible test results this method requires considerable expertise from the operator in the preparation and packing of hide powder filter cartridges. In addition, the time for the filtration can be very long. The co-polymers of vinylimidazole and vinylpyrrolidone are used for removing polyphenolic compounds and metals from wine. This polymer-based powder offers a simple and practical alternative to hide powder for the routine testing of synthetic tanning agents, such as in a manufacturing facility. The reproducibility and precision of repeat testing is better for the polymer-based powder. As the two methods use different adsorbing substrates, the value for the adsorbable fraction will be different from one another. This International Standard specifies a simple and practical method of determining the adsorbable fraction of synthetic tanning agents using a polymer-based product. It is particularly suitable for measuring the batch-to-batch consistency of synthetic tanning agents. ISO 14088 uses hide powder for determination of the tanning component in tanning agents. This traditional method is, however time-consuming and is not suitable when the results are needed in a short period of time. An acidified synthetic tanning agent solution and an insoluble copolymer product are mixed at room temperature. The insoluble copolymer absorbs polyphenols from the tanning agent. The dry content of the solution before and after mixing with the absorbing copolymer are measured. The difference is the adsorbable fraction, called the tan content. This document (EN ISO 17489:2013) has been prepared by Technical Committee CEN/TC 289 "Leather", the secretariat of which is held by UNI (Italy) in collaboration with the International Union of Leather Technologists and Chemists Societies (IULTCS). The responsible German committee is Working Committee NA 062-05-52 AA "Chemische Prüfverfahren für Leder" ("Chemical test methods of leather") at the Materials Testing Standards Committee (NMP) at DIN.