Iodine Index

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					                                                 Håvard Meling 3IBA 2000

                                                   Iodine Index
Aim: plan an experiment to determine the saturation level, or their iodine number, of three different lipids. Less
iodine number more saturated. We should get numerical data, not just observations. This lab should only be
evaluated on planning B.

Hypothesis: Addition of I2 to an unsaturated molecule will cause the double bonds to break from to form
single-bonded carbon atoms. Since saturated and unsaturated fats are colourless and iodine is coloured, the
reaction mixture of an unsaturated fat and iodine will turn from a red-violet to a clear solution as the iodine is
used up in the addition reaction. If fat contains no double bond it will not react with iodine. Thus the solution
will not clear. The definition of the Iodine index is the NR of grams of iodine being reacted with 100 grams of


                                    Heating of

                                                                           Using a buret to
                                                                           see how much
                                                                           iodine being used:                    Buret
  Weighting of
     lipid:                Beaker with

                                                                     Beaker with

                                                                                                                     Beaker with
                                                                      Tripod                                         lipid

                    Digital Scale
                                                                                                                     A magnetic
                                                                        Ring stand                                   stirrer is
                                                                                                                     placed under
                                                                                                                     the beaker
                                                                                                                     and a magnet
                                                            Burner                                                   in the bottom
                                                                                                                     of the beaker.

1.    Digital Scale
2.    6 beakers
3.    Thermometer
4.    Magnetic stirrer
5.    3 magnets
6.    Tripod
7.    Burner
8.    Buret
9.    Safety goggles
10.   Matches
11.   Funnel (to prevent spills)
12.   Knife (to cut up butter)
13.   Buret/test tube clamp

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                                              Håvard Meling 3IBA 2000

1.   Three different fats or oils
      Olive Oil
      Cod-liver oil
      Butter (Tine Smør)
2.   Iodine solution (1g/mL iodine)

1.   First we have to weigh exactly a chosen NR of grams of Lipid. We use a digital scale for this purpose. It
     would be wise to have the same amount of each of the three lipids. We will try to keep all factors the same
     for the different lipids. In our experiment we used 50 g of each lipid. This might be a little to much. 10
     grams of lipid could be appropriate since we don’t need so much Iodine to make the experiment work. We
     know from theory the approximate iodine NR of the different lipids, so we have an idea of the ratio. We can
     use this knowledge to concentrate our values on what we think the answer should be. I have drawn the
     weighting on the drawing. The lipids were placed in three different beakers. We record the weights in a

2.   We have to make a solution of Iodine. In our lab we had 0,3g/100mL of iodine. This was a solution of
     KI(potassium iodide). This means that we had 0,003g of iodine pr ml of solution. Clearly this will be to little
     to observe any change. The solution we used had a colour of rust. This colour comes from the potassium not
     the iodine. Since there was so small amounts of iodine present, it’s colour red-violet could not be observed.
     If we make a solution or have a solution with more Iodine present we could use our hypothesis. This could
     for instance be one solution where we have 1 g of iodine pr ml of solution. We record the grams of iodine
     pr. ml solution in a table.

3.   The weighted lipids should be warmed. We had to make the butter turn into liquid phase. We tried to make
     sure that the lipids held the same temperature. This we did to make sure that all factors were the same. We
     used a thermometer to read of temperature. We heated it with a burner under a tripod with the beaker with
     the lipid on top. This is shown in my drawing. We also needed to warm up one extra set of lipids to be used
     to comparison when doing the reaction between the lipid and iodine. We need the set to see when the
     solution is cleared. We record the temperature in a table.

4.   We had to set up our stand as shown in the drawing. We connected the buret to the ring stand with a buret
     clamp. Under the buret we placed the different beakers with lipids. Inside the beaker we placed a magnet.
     Under the beaker we had a magnetic stirrer. We need the stirrer both for not letting the butter turn into solid
     again, and to mix iodine and the lipids. We place the iodine solution into the buret. The main idea is to drop
     little by little of the iodine into the beaker and see if the reaction mixture clears or if it is red –violet (colour
     of iodine). We then record our results in a table. We can read of from the buret how much iodine we used
     before the reaction mixture didn’t clear anymore. We use our comparison beakers to see if the reaction
     mixture has cleared or not.

5.   We use the results recorded in 1, 2 and 4 to calculate the iodine number. We know the amount of lipid we
     have from 1. We know how many grams of iodine in solution from 2. We know how many ml of iodine
     solution we have used from 4. We can therefore calculate how many grams of iodine we used before the
     reaction was complete. The iodine number is defined as NR of grams of Iodine absorbed pr 100 grams of
     lipid. We use cross multiplying to find out how many grams of iodine in experiment we had pr 100 grams of

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