Palintest AP188 Alkalinity-Total Reagent Tablets 250 per box. The Palintest Alkaphot test is based on a unique colorimetric method and uses a single tablet reagent. The test is simply carried out by adding a tablet to a sample of the water. Under the conditions of the test, a distinctive range of colours from yellow, through green, to blue is produced over the alkalinity range 0-500 mg/l CaCO3. The colour produced in the test is indicative of the alkalinity of the water and is measured using a Palintest Photometer.