that in a lyophobic colloid.
We found that similar coagulation curves could be produced with sodium, calcium, and aluminum salts and that the only real difference was in the position of the vertical region of the sigmoid curve (12). The effect of valency was approximately as would be predicted by the Schulze-Hardy rule. The suspensions coagulated with the calcium chloride were particularly interesting since, with the highest concentration of electrolyte used, a further step in the sedimentation height curve was observed. Compatibility tests between the electrolyte and surfactant showed that, at this concentration, slight precipitation occurred. We interpret this as being perhaps the point of transition between coagulation and flocculation.
Ecanow et af. (5, 7,18) appear to argue that since coagulation and flocculation must produce qualitatively different results and that we merely found quantitative differences, we could not be studying two different phenomena. We find it difficult to answer such circular reasoning. We would still maintain, on the basis of carefully controlled experiments whose results are compared with fundamental theory, that both coagulation and flocculation can produce suspensions that remain free from caking on storage.