BS ISO 19662:2018 pdf free.Milk – Determination of fat content-Acido-butyrometric (Gerber method). The amyl alcohol shall be composed of at least 98 % in volume of primary alcohols 3-methylbutan- 1-ol (boiling point 131,4 °C) and 2-methylbutan-1-ol (boiling point 128,0 °C), the only permissible impurities being 2-methylpropane-1-ol’) and butan-1-ol. The ratio of the two isomers shall be 91 % ± 2% of 3-methylbutan-1-ol to 9% ± 2% of 2-methylbutan-1-ol in the volume of primary alcohols as defined above. It shall be exempt from all compounds which may have an influence on the result given by the acidobutyrometric method, such as secondary amyl alcohols, 2-methylbutan-2-o12), furfural, petroleum and benzene derivatives. Only traces of water can be tolerated. 5.2.2 Physical appearance Clear and colourless. 5.2.3 Density p20= 0,813 g/ml ± 0,005 g/ml at 20°C. 5.2.4 Furfural and other organic impurities The absence of impurities is revealed if the colour of a volume to volume mixture of amyl alcohol and sulphuric acid remains yellow or light brown. 5.2.5 Distillation range When distilled at a pressure of 1 013 mbar (760 mm of Hg), a volume fraction of not less than 98% shall distil below 132°C and a volume fraction of not more than 5%…