白云石中钙镁含量的测定研究

经典测定白云石中钙、镁含量的方法是先用EDTA标准溶液测定钙镁总量再测定钙含量，然后运用差减法计算出镁的含量。采用在指示剂中加入表面活性剂的方法，使其在滴定过程中生成三元络合物，提高了显色反应的灵敏度，增加有色化合物的稳定性。实验中确定了十二烷基硫酸钠作为加入指示剂的表面活性剂。在测定钙的过程中，苦味酸的加入消除了终点时微红色的干扰，终点易于观察和判断。与普通法相比，新方法终点变色敏锐，准确度、精密度均较高，结果令人满意。

Study on the determination of calcium and magnesium in dolomite

Traditionally, the EDTA standard solution was used to determine the total content of the calcium and magnesium firstly. Then determine the content of calcium. At last,the content of magnesium can be obtained by subtraction. When the surface active agent was added into the indicator,the ternary complex was formed in titration and the stability of colored compound was enhanced,the color change at the end point was distinct. The lauryl sodium sulfate was confirmed as the surface active agent in the indicator. In the determination process of the calcium,the disturbance of the reddish color in the end point was eliminated by adding the bitter acid,which makes it easy to observe and judge in the end point. The experimental results showed that the color variation of end point was sensitive comparing with the ordinary method. Meanwhile, the new method has a high accuracy and precision and the result was satisfying.