A re-evaluation of the method for available lime determination

The available lime value of quicklime and hydrated lime is a measure of the material's ability to undergo a chemical reaction and is therefore an impo rtant quality control parameter. The analytical method for determining avai lable lime is based on the solubilization of calcium by a sugar solution, f ollowed by a titration against a standard acid. Since the current method is slow and tedious, several variables were investigated in an effort to find the most economical, quick and reliable way to measure available lime. It was found that the shaking time of 4 h could be reduced to 30 minutes and t hat the 6 h settling time could be eliminated by an additional filtering st ep in the standard procedure. The concentration of the sugar solution used should not be below 7.5 %, but a magnetic stirrer can be used as a means of agitation instead of a mechanical shaker, while the use of an ultrasonic b ath is not recommended. A comparable extraction utilising microwave technol ogy has been developed in which 0.05 g of sample is heated with 10 ml of su gar solution, at 600 W for 5 minutes.