Final answer:
The exact time for shaking the fuel/water mixture in a fuel system icing inhibitor (FSII) analysis is not provided in the references, but analytical chemistry practices emphasize thorough and complete mixing of solutions.
Step-by-step explanation:
When performing a fuel system icing inhibitor (FSII) analysis, the appropriate procedure for shaking the fuel/water mixture in a separatory funnel is not exactly specified within the provided references.
However, general analytical chemistry methods suggest similar processes that can be drawn upon, such as dissolving a solute or allowing a gas to bubble through a solution for a set period of time. The thorough mixing of a solution is often achieved by swirling or inversion, while ensuring complete interaction between the reagents for effective reaction or analysis.