Lovibond comparator

Another bit of old scientific apparatus. It's used to determine the intensity of colour of liquids. The coloured solution is put in a glass tube, which is inserted into the comparator and compared with a series of coloured glass discs until the nearest possible match is found. The intensity of the colour is related to the concentration of some chemical species in the solution.

Different sets of coloured discs are available. The two in the photo are for iron and phosphate. Although the comparator was invented in the 19th century, modern equivalents are still available today.