Alkane and bromine water. Test tubes showing the initial (left) and final (right) appearance of a mixture of an alkane and bromine water, showing how the solubility of bromine (orange, a halogen) varies. The alkane used here is hexane, which as a hydrocarbon is immiscible with water and forms the upper layer in the two test tubes. At left, the hexane layer has just been added to the bromine water and the bromine is immediately starting to dissolve in the hexane layer. After shaking and being allowed to stand, the two layers separate again (right), but the bromine is now dissolved in the hexane rather than the water.