The author replies to Clark
No need to pour your Lambert beer down the drain!
The original buckminsterfullerene data collected
for Figure 1 are as follows:
0.05 mg/mL, 79%T
0.10 mg/mL, 70%T
0.20 mg/mL, 60%T
0.36 mg/mL, 39%T
0.42 mg/mL, 31%T
Indeed, a plot of %T versus concentration gives the
expected curve when plotted carefully. The curve fit for Figure 1 was drawn by a program that assumed a linear function.
Conversion of the above %T values to absorbance values using the equation A = 2 - log %T gives the following data for the above five samples:
0.05 mg/mL, 0.102A
0.10 mg/mL, 0.155A
0.20 mg/mL, 0.222A
0.36 mg/mL, 0.409A
0.42 mg/mL, 0.509A
A plot of absorbance versus concentration gives a linear curve as expected (slope =
1.070 ± 0.0758, R2 = .9926). Since the CBL data were obtained with a colorimeter probe that measures percent T directly, we wanted to keep the data in the original form. Thank you for pointing out the graphing error. Yet another reason why (in the days when such instruments only measured percent T) we taught students to convert %T values to A values before plotting in Beer's law experiments.
Not even the mighty buckminsterfullerene molecule is able to exhibit chemistry that
revokes Beer's law.
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