BS EN ISO 4048:2018 pdf – Leather – Chemical tests – Determination of matter soluble in dichloromethane and free fatty acid content.
1 Scope This document specifies a method for the determination of the substances in leather which are soluble in dichloromethane. This method is applicable to all types of leather. Not all fatty and similar substances can be extracted from leather with organic solvents; they may be in part soluble and partly bound to the leather. On the other hand, the solvent can dissolve non-fatty substances, for example sulfur and impregnants, both of which cause difficulty in the determination of the acid value and saponification value of the fat. This document includes two techniques for extraction of the fatty substances: 1) extraction using the Soxhlet apparatus; and 2) extraction using a pressurized extraction system. As the extraction is frequently done in conjunction with determination of the free fatty acid content of the leather, a suitable procedure for determination of the free fatty acids extracted by this method is included. The apparatus and technique described in this method are also suitable for the extraction by solvents other than dichloromethane (although the temperature conditions may need to be varied for high pressure extraction). 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 2418, Leather — Chemical, physical and mechanical and fastness tests — Sampling location ISO 4044, Leather — Chemical tests — Preparation of chemical test samples ISO 4684, Leather — Chemical tests — Determination of volatile matter
3? Terms? and? definitions For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https://www.iso.org/obp — IEC Electropedia: available at http://www.electropedia.org/ 3.1 extractable substances fats and other soluble matter which can be extracted from leather with dichloromethane 3.2 free fatty acid content fatty acid content of the extractable substances (3.1) as determined by this method and expressed as oleic acid
4 Principle The prepared leather is extracted with dichloromethane. The solvent is evaporated from the extract, which is then dried at 102 °C. Subsequent analysis can then be performed on the resulting extract to determine the free fatty acid content of the leather. 5 Reagents During analysis, use only reagents of a recognized analytical grade. 5.1 Determination of substances soluble in dichloromethane. 5.1.1 Dichloromethane, CAS No. 75-09-2. NOTE Dichloromethane which has been used for this analysis can be recovered and reused after distillation. WARNING — Dichloromethane has toxic properties and should be used with caution. The supplier’s handling instructions should be followed. 5.2 Determination of free fatty acid content of the leather. 5.2.1 Mixed solvent, a mixture of equal volumes of diethyl ether and 95 % (volume fraction) ethanol, neutralized with 0,1 mol/l sodium hydroxide (phenolphthalein is used as the indicator). If, for any reason, other solvents are used, the solvent or solvents used shall be stated in the test report. 5.2.2 Sodium hydroxide, 0,1 mol/l standard solution. 5.2.3 Phenolphthalein indicator solution, 10 g/l prepared in 95 % (volume fraction) ethanol. In determinations on dark coloured solutions, observation of the end point of the titration may be facilitated either by the substitution of thymolphthalein or alkali blue 6B for phenolphthalein. Alternatively, 1 ml of a 0,1 % solution of methylene blue can be added to each 100 ml of the phenolphthalein solution before titration. Phenolphthalein should be used as the preferred option if possible.
6 Apparatus 6.1 Soxhlet extraction apparatus, including an extraction flask of suitable capacity and a condenser, or pressurized extraction system, including extraction flask of suitable capacity, or any other validated equipment giving equivalent results to Soxhlet can be used. 6.2 Filter paper thimbles, of suitable sizes, or suitable glass? filter? bells. 6.3 Oven, capable of being maintained at (102 ± 2) °C. 6.4 Analytical balance, capable of weighing to an accuracy of 0,1 mg. 6.5 Desiccator, suitable for cooling the extraction vessels. 6.6 Glass wool or cotton wad, or something equivalent. If a cotton wad is used, this shall be pre-extracted in dichloromethane (5.1.1).