MODEL RELEASED. Student using a colorimeter to measure the hue of a sample of copper sulphate (CuSO4). The test tube is placed into a cavity in the device and filtered light is passed through the sample. The colour composition of the sample is determined by how much of each colour of light is absorbed by the sample. A blue-coloured solution, like CuSO4, will allow blue light through, but will block other colours of light. A digital display (not seen) will present the results. The unknown concentration of a CuSO4 solution can be derived from colorimetry, by referencing to a solution of known concentration.