1. Ensuring Reliability
June 2013
Paul Beaumont

2. Colorimetry

3. [Evaluating experimental procedures p. 50]
Learners should be able to…: …
identify sources of error in measurements and observations
identify and comment on the reliability of results
...

4. Skills of scientific experimentation, investigation and enquiry
Evaluating (p 8)
Learners should be able to…: …
identify sources of error in measurements and observations
identify and comment on the reliability of results
...

5. [Laboratory Techniques p. 21]
Use a colorimeter or spectrophotometer to calibrate a known solution and determine an unknown.

6. Colorimetry How ‘good’ is my colorimeter?
Is it equally ‘good’ at all wavelengths?
Do all the colorimeters in my department give me the same answer?

7. The Samples

8. The Samples %T LEE Filters – range of filters 71
Neutral density options
50% transmission
= 0.30 absorbance
[A = 2 - log (%T)] %T 71 50 25
12.5
6.25

9. Beam Direction R = Reference T = Test Set filter to 440 nm
Empty cuvette as blank
Zero (R!) colorimeter
Measure (T!) & record absorbance
Add a ND filter - record absorbance
6. Repeat with extra ND filters
7. Plot data
Repeat at 520 nm
R = Reference
T = Test