抄録
Kaolin has been used conventionally for preparing the standard solution of turbidity in the water analysis in Japan. But the variation of turbidity of kaolin suspension are remarkable owing to the origin of kaolin. Satisfactory standard was able to be prepared, when the particle size of kaolin was unified by sedimentation method. The standard solution prepared by this new method was much more stable than the conventional standard solution. The outline of the preparation is as follows : An adequate amount of kaolin is dispersed with 0.002 M sodium pyrophosphate solution, mixed thoroughly with homogenizer (8000 rpm), and settled in a tall cylinder for 24 hours. The upper turbid layer thus obtained is transferred to a tall cylinder and settled for about 100 hours. The upper layer is discarded and the residual precipitate is dispersed in a fixed volume of water. The standardization method of this suspension will be reported in the other papers.
