Colorimeters

There are a number of instruments which can be used to determine the concentration of colored solutions. Among the simplest and most common are the Spectronic 20 and Spectronic 21. They are commonly called the Spec 20 and Spec 21.

Examples 8 and 9 in your workbook have diagrams and instructions for their use as do the pages in this section (links are to the left).

When you are in the lab, you should practice operating these instruments by finding and measuring the practice solutions in the lab. With each practice solution there will be some appropriate information, such as the wavelength to be used and so forth. Follow the operation steps in example 9, except that the instruments will probably already be turned on and warmed up.

After you have practiced operating the instruments using the practice solutions, there remains the problem of actually figuring out the concentration of a solution from the absorbance measurements that can be made using the colorimeters. That will be dealt with in the section on Calculations for Colorimetry. After that you will put it all together by doing the Lab Work necessary to obtain the data needed to experimentally determine the concentration of an unknown solution.

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E-mail instructor: Sue Eggling