When measuring out amounts of liquid I will make sure that the bottom of the meniscus of the circle of the top of the liquid is on the measuring line.
I will use a 10cm3 pipette to put Benedict’s reagent in to 13 boiling tubes and put them in to a water bath at 100oC for 3 minutes to warm up. The reason that I have used 13 boiling tubes of Benedict’s is so that one can be used for the unknown glucose solution, another as a control for the Benedict's.
I will then remove 5cm3 from each of the test tubes of glucose solution, place them in to a boiling tube of Benedict’s reagent and shake the boiling tube. I will label each of the boiling tubes with a pencil. The boiling tubes will then be placed back in to the water bath at 100oC for 10 minutes.
Whenever I put a number of test tubes in to a water bath, I will place them in a rack, then place the whole rack in the water bath and on removing, remove the whole rack. This will ensure that all the test tubes have had the same amount of time in the water bath.
When the boiling tubes have cooled I will filter the contents using filter paper folded in to a cone shape and dispose of the residue.
I will then use a teat pipette to put each of the filtrates in to a cuvette, being cautious not to touch the edges of the cuvette as finger prints can affect colorimeter readings.
I can now place each of the cuvettes in to the colorimeter to receive a % transmission of light.
I will repeat this experiment three times, and find an average of the final colorimeter result to reduce the affects of anomalies on my results. I will record my finding in a table as below.
I will then plot a graph including the average results for test tubes 1-11. I can find the composition of the unknown glucose solution by finding where the average results from test tube 13 lie on the line.
