Transfer 25 ml aliquots of each of these beer samples into separate 50 ml volumetric flasks. Add 5ml of p- rosaniline colour reagent swirl to mix and add 5 ml of formaldehyde swirl again to mix and make to volume with water. Hold for 30 min in a water bath at 25 องศาเซลเซียส and measure the absorbances at 550 nm in 10 mm cells against the sample with zero addition of solution B