PAG05 = COLORIMETER

Question 1

How do you first set up the colorimeter?

Answer 1

1. Switch the colorimeter on and leave to stabilise for 5 minutes.
2. Select the red filter

Question 2

How do you set the filter for benedict’s test?

Answer 2

for Benedict’s – use a complementary colour to starting
solution) on the colorimeter. If using Benedict’s, centrifuge the solution or
allow to sit to precipitate out the copper solid.

Question 3

Next how do you set the colorimeter?

Answer 3

set to zero using a cuvette 3/4 full of distilled water;
Ensure the cuvette is placed into the colorimeter so the light passes through the clear
sides.

Question 4

Then how do you set up the slides?

Answer 4

Make sure the slides are clean and there are no bubbles in the solution.
Using a pipette, fill the cuvette ¾ with the sample.

Question 5

Then how do you read the colorimeter?

Answer 5

Place in the colorimeter and read the absorbance of light.
Less light is absorbed by the solution in a paler solution, so there is a greater
transmission for a paler solution.

Question 6

What is the full method of using a calorimeter?

Answer 6

1. Switch the colorimeter on and leave to stabilise for 5 minutes.
2. Select the red filter (for Benedict’s – use a complementary colour to starting
   solution) on the colorimeter. If using Benedict’s, centrifuge the solution or
   allow to sit to precipitate out the copper solid.
3. Set the colorimeter to zero using a cuvette ¾ filled with distilled water.
4. Ensure the cuvette is placed into the colorimeter so the light passes through the clear
   sides.
5. Make sure the slides are clean and there are no bubbles in the solution.
6. Using a pipette, fill the cuvette ¾ with the sample.
7. Place in the colorimeter and read the absorbance of light.
8. Less light is absorbed by the solution in a paler solution, so there is a greater
   transmission for a paler solution.

Question 7

How do we use a calibration curve for absorbance?

Answer 7

1. Standard solutions of the reducing sugar should be used. Standard solutions are those
   of known concentration.
2. Carry out a Benedict’s test on each sample
3. With the colorimeter, measure the percentage transmission for each sample.
4. Plot a graph of transmission against reducing sugar concentration.

Question 8

What will the results show for reducing sugars?

Answer 8

more transmission/less absorbance = more sugar present

greater concentration