This standard is applicable to the determination of water-soluble matter, water-soluble inorganic matter, and water-soluble organic matter in various types of leather. The determination of water-soluble content depends on the degree of leather grinding, extraction temperature, extraction time, and the ratio of leather to water. To obtain comparable results, strict adherence to experimental conditions is necessary. In any case, any ammonium salt exists in solution as a water-soluble organic substance in the form of ammonium sulfate. Definition 1.1 Water soluble substance: The substance extracted from leather with water under the conditions specified in this standard. These substances are mainly organic tannins, non tannins, and mineral salts. 1.2 Water soluble inorganic matter: The sulfate ash content of the water soluble substance prepared by this method

1.3 Water soluble organic matter: The difference between total water soluble matter and inorganic water soluble matter. The prepared sample is extracted with water under specified conditions, the extract is evaporated, dried at a temperature of 102 ± 2 ℃, and its water-soluble content is measured. Then, the residue is subjected to sulfation and ashing at a temperature of 800 ℃, and water-soluble inorganic substances are measured. The difference in measurement results between the two refers to water-soluble organic matter. The reagents used must be analytically pure. The water used is distilled water or at least of the same purity as distilled water A sulfuric acid solution of approximately 2N

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