The term colloid is now generally applied to any system which contains a large area of phase boundary per unit volume. There can be no doubt that clay minerals rank as colloids and it is very desirable that clay mineralogists and colloid chemists should be brought together as in the present meeting.

The skill displayed by clay mineralogists in overcoming the technical difficulties with which they were confronted has been remarkable, and the benefits derived from their painstaking investigations are already being felt outside the immediate field of their studies and particularly in other branches of colloid science. To have precise information about the dimensions and crystal structure of the particles in a colloidal system can make all the difference between success and failure in distinguishing between alternative explanations of colloidal phenomena.