用咩化學方法可以分出oil is saturated or unsaturated?

experiment1,oil/fat were add to bromine water,,then.....all of the oils including animal fat change bromine to colourless......why???
if the oil or fat have its own colour(egg yolk),then the change of bromine water cannot be be observe.Can the experiment be done by using chlorine instesd of bromine?
experiment2,係oil/fat added to acidify KMnO4,however,oil didn't dissolve in KMnO4...how can i improvide,or just delete this experiment?
why alcohol turn KMnO4from purple to brown?