Testing if photosynthesis had taken place in the leaf

On 28 July2010, we had an experiment in the lab about finding out if photosynthesys had taken place in the leaf. First, we have to boil the leaf for 1-2 mins to break the cell structure. Then, we stirred the leaf in a test tube of alcohol to remove chlorophyll. After that, we put the leaf on a white tile and dropped iodine on it. The result was supposed to be the iodine turning blue, but my experiment failed and my iodine was still brown. What we could conclude was that photosynthesis had taken place in the leaf.