ISO 660-2020 pdf download

ISO 660-2020 pdf download.Animal and vegetable fats and oils – Determination of acid value and acidity. 4 Principle The sample is dissolved in a suitable solvent mixture, and the acids present are titrated with an ethanolic or methanolic solution of sodium or potassium hydroxide. The methods specified in 9.1 and 92 are reference methods. 5 Reagents WARNING — Attention Is drawn to regulations that specify the handling of hazardous substances. Technical, organizational and personal safety measures shall be followed. Use only reagents of recognized analytical grade, unless otherwise specified. 5.1 Solvent A for the solvent mixture (u), ethanol, volume fraction, q ‘ 96 %. As a replacement, propan-2-ol, volume fraction, p 99 %, may be used. 5.2 Solvent B for the solvent mixture (u), diethyl ether, peroxide-free. As a replacement, tert-butyl methyl ether, light petroleum (boiling range 40 °C to 60 °C) or toluene may be used. WARNING — Diethyl ether Is very flammable and may form explosive peroxides. Use with great caution. 5.3 Solvent mixture, mix equal volumes of solvents A (51) and 13 (52). Volume fraction of A: q = 50 ml/100 ml; volume fraction of B: q, = 50 ml/100 ml. For hard or animal fats, a solvent mixture of one volume of solvent A (e.g. 25 ml) and three volumes of tert-butyl methyl ether or toluene (e.g. 75 ml) is recommended. Neutralize, just before use, by adding potassium hydroxide solution in the presence of 0,3 ml of the coloured indicator solution per 100 ml of solvent mixture. For the titration with aqueous KOI-I, the solvent propan-2-ol may be used. 5.4 Ethanol or methanol, of minimum volume fraction, q = 95%. 5.5 Sodium hydroxide or potassium hydroxide standard volumetric solution, made up in either ethanol or methanol. Substance concentration c(NaOH) or c(KOH): 0,1 mol/l and 0,5 mol/l, respectively. The exact concentration of the sodium hydroxide solution (or potassium hydroxide solution) shall be known or checked prior to use. NOTE The ethanolic/methanolic sodium/potassium hydroxide solution can be replaced by an aqueous sodium/potassium hydroxide solution, but only if the volume of water introduced does not lead to phase separation. 5.6 Thymolphthalein (CAS number: 125-20-2) or Alkali blue 6B (CAS number: 1324-76-1) solution in ethanol, mass concentration, p = 2 g/100 ml or, failing that, Phenolphthalein (CAS number: 77-09-8) solution in ethanol, mass concentration,p = 1 g/100 ml. NOTE 1 Phenolphthalcin is classified as a carcinogenic. mutagenic or toxic for...