The Japanese archipelago, in the temperate zone, has been affected by volcanic and hot spring action in many geological periods including the Recent one. Complicated clay mineral assemblages have been formed by alteration of volcanic glass both by weathering and hydrothermally, and have been studied by the writer and his collaborators (Sudo, 1950b, 1951; Sudo, Minato and Nagasawa, 1951; Sudo and Ossaka, 1952). The present account, based on these studies and on more recent data, deals with acidic to intermediate types of volcanic glass, which are widely distributed in rocks and soils throughout the islands.

The catalytic influence of a Spanish kaolin and bentonite on the vapour phase oxidation of 96% ethyl alcohol has been studied, using different temperatures and varying proportions of air. Consideration has also been given to the changes produced in the activity of these minerals by previously saturating with different exchange cations or subjecting them to the action of acids.

Up to now no method seems to have been found for carrying out laboratory syntheses of clay minerals in conditions similar to those obtaining in soils. Such a method would be of especial value because it would lead to the possibility of determining the conditions of formation of clay minerals in the natural state.

The techniques previously employed in this laboratory for removing free iron oxide from soil clays were the acid ammonium oxalate and the aluminium-ammonium tartrate methods (Tamm, 1922; Dion, 1944). Since both had disadvantages, especially when determining the iron by sodium salicylate (Scott, 1941), the use of sodium hydrosulphite, Na2S2O4, (Galabutskaya and Govorova, 1934; Deb, 1950) was fully investigated in the hope that it might lead to the development of a satisfactory, completely inorganic procedure.

Although many investigations have been carried out on the problem of soluble salts, it is not possible at the present day to state definitely at what percentage content and what composition soluble salts are to be reckoned as harmful, because in judging this matter not only the quantities, but also other things, such as for instance the pore space, play a big part.

In a letter to “Nature” in 1937, Mitchell and Muir directed attention to the existence, in certain Scottish soils derived from basic igneous parent material, of a very high total cation exchange capacity relative to the clay content—as high as 9 m. eq./gm. clay in some cases. These values were so high as effectively to preclude the possibility of the clay itself being solely responsible for the cation exchange capacity, and in fact in those cases where it was very high relative to clay content, the clay content itself was generally low, so that the cation exchange capacity of the whole soil was quite moderate, of the order of 0·3 m. eq./gm. The high cation exchange capacity could not be due to organic material, for it often occurred in lower layers where the organic matter content was likely to be low.