Colorimeter

The colorimeter is another one of Joe's essential lab equipment. It is a device used in colorimetry to determine the concentration of a solute in a solution that has colour by measuring the absorbance of specific wavelengths of light by the solution. With this device and concept, the Beer-Lambert law is applied. This law states that the concentration of a solute is directly proportional to its absorbance or colour intensity. However, there are many other factors that may affect the above statement. For instance, how intensely a substance absorbs colours may depend on the chemical being used, and its arrangement of electrons and energy levels. Since the concentration of a solute is proportional to its absorbance, then as concentration increases, the spectrum shown has fewer colours. Also, not only does the concentration of the solute affect the results, but so does the thickness of the solution. The absorbance is also directly proportional to the thickness of the substance. So overall, more intensely coloured compounds possess a more intense hue than less concentrated compounds. This was evident in the dilution lab that I did last year, where a series of liquid compounds were prepared through dilution, and each compound had a different concentration, evident by the varying colour intensities.

The increasing intensity of hues (right to left) indicates increasing concentration.

Joe uses the colorimeter by first selecting the appropriate wavelength, depending on the sample, to be measured, and then continues to carry out operating the machine to receive an absorbance value from the meter, and then this value can be used to find the concentration of the solution with Beer's Law.

A typical colorimeter.