该方法基于称量试样，将其溶解在水中，将溶液转移到两个纳氏比色瓶中，通过向其中一个纳氏比色瓶中添加新制备的氨化硝酸银溶液制备试验溶液，并充分混合，向另一个纳氏量筒中加入氢氧化铵溶液和水，并充分混合，使溶液静置2分钟，然后比较两种溶液的颜色和浊度，制备空白溶液。

The method is based on weighing a test portion, dissolving it in water, transfer of the solution to each of two Nessler colour-comparison cylinders, preparing a test solution by adding freshly prepared ammoniacal silver nitrate solution to one of the Nessler cylinders and mixing well, preparing a blank solution by adding ammonium hydroxide solution and water to the other Nessler cylinder and mixing well, allowing the solutions to stand for 2 min, and comparing the colour and turbidity of the two solutions.