The Tintometer Ltd
A test sample is mixed in a glass tube with a colorigenic reagent. The glass tube is inserted in the comparator and compared with a series of colored glass discs until the nearest possible match is found. The concentration of the substance in the test sample is indicated next to the disc selected.
Neil Squires (Royal Hospital for Sick Children, Edinburgh) and Barry Coombes (The Tintometer Ltd)
Johnston SF. Lovibond comparator. In: Bud, R. and Warner, D.J. (eds.) Instruments of Science: A Historical Encyclopedia. Series: Garland reference library of social science (936). Garland, New York, USA, 1988;129-130; http://en.wikipedia.org/wiki/Lovibond_comparator