Used for measuring Blood Sugar levels. This simple but effective method for measuring a colour based chemical analysis was developed by a Pharmacist in Salisbury, Wiltshire, and initially marketed by a local company there. The chemical reaction in a test tube is quanitated by comparison with a graded series of coloured glass standards chosen for the particular test in progress. Various tests became more reliable and useful in the care of patients with diabetes, renal disease and liver disorders.

Although this sort of apparatus ought to have been rendered obsolete by photoelectric colorimetry in the 1940’s, its use continued for some 20 years in smaller hospital labs. It is straightforward and fast to use, but it is very limited in many aspects of analytical quality.

For environmental water analysis ‘in the field’, for example chlorine analysis ins swimming pool water, it is still sold and used in barely modified form to this day.