Practical 5

Practical: Amalyse PH test

Part 1:Place one dropof iodine solution into each well of the spotting tile get three test tube in the first one 2cm cubed of starch solution 2cm cubed of amylase solution and 2cm cubed of PH5 buffer solution (Ph buffer solutions are used to control the Ph)

Part 2:Place all three test tubes in a water bath at 30 degrees celcuis.Leave them for 10minutes to allow the solutions to reach the correct tempreture.Now combine the three solution into one test tube and mix with a stirring rod.Return the test tube to the water bath and start the stop watch

Part 3:After 30 seconds use the stirring rod to transfer one drop of the solution on to the well of the spotting tile which contain iodine the iodine should turn blue black showing that starch is present 

Part 4:We now take a sample every thirty second and we continue until the iodine remains orange.When the iodine remains orange starch is no longer present.(the reaction has completed) Record time for this in results.

Part 5:We now repeat the whole experiment several times again using different Ph buffers for example Ph 6,7,and 8 .

Problems of the experiment :

We are only taking samples every 30 seconds this means we only have an approximate time for the reaction to complete  we can solve this by taking the sample every 10 seconds.

We are also looking for a time when the iodine does not go blue-black this is not always obvious the colour change tends to be gradual so the black blue is sometimes slightly mixed with the orange and is hard to see so it can be hard to see when the reaction is finished.to address this problem you can ask several peopleto observe the spotting tile to decide when the reactionhas completed.