“…Experimental study of the caking strength of NaCI, (NH4)2S()4, KC1, NaN03, and urea, etc. have been carried out by several investigators (Adams and Ross, 1941;Ross et al, 1945; Ezaki and Sugiyama, 1960;Nash et al, 1965; Tucker and Roy, 1969;Masuzawa, 1970). However, as to the theoretical point of view, no paper has been available to the writer's knowledge.…”