(t. W. Robinson 291 



No attemj)t lias been made to follow the chemical changes involved 

 in the oxidation of soil organic matter by hydrogen peroxide. It may be 

 mentioned that the soluble compounds formed appear to form a very 

 suitable medium for the development of moulds and fungi as, when 

 exposed to air, they quickly become covered with a scum on which 

 growths appear. The products of oxidation would be well worthy of 

 chemical examination. 



The results obtained particularly in the case of Welsh soils indicate 

 that the figures obtained for clay by the ordinary method may be mis- 

 leading and that there are considerable quantities of 'clay' which are 

 wrongly grouped with the coarser fractions. In other words the ordinary 

 method fails to secure the prime particle structure. This defect in the 

 standard method may operate to some extent even in soils with smaller 

 amounts of organic matter, for in every case larger figures were obtained 

 for the clay after peroxide treatment. 



Treatment with peroxide offers a convenient means of removing 

 organic matter from soil without altering the mineral portion. In these 

 experiments it was not found possible to remove all the organic matter. 

 Complete removal might be effected by successive treatment with 

 peroxide. It would appear, however, that the humified organic matter 

 is completely oxidised or rendered soluble for the dark colour is removed 

 even from peat soils and the oxidised soil has the appearance of a raw 

 subsoil. The unoxidised material in such cases appears to consist entirely 

 of structural organic matter, a circumstance which suggests that only 

 humified matter is attacked. 



{Received July Sth, 1922.) 



