Colorimetry - BTEC applied science chemistry

Hi, I was just wondering if I could have some help. I recently missed a lesson due to illness and we went over why we use red in a colorimetry practical when using a blue copper sulphate solution. Any help would be great???

Thank you!!

Reply 1

charco

Study Forum Helper

Original post by Medavies

The solution appears blue because it transmits blue light and absorbs the other wavelengths. The colours absorbed by a solution is called the complementary colour. There are charts to show you the complementary colour of solutions.
https://en.wikipedia.org/wiki/Complementary_colors#/media/File:RGB_color_wheel.svg

If a solution appears blue, then it absorbs in the red/orange region of the spectrum. To increase the sensitivity of the colorimeter the filter only provides light of a complementary colour.