PROCEEDINGS OF SECTION K. 653 



These bacterio-toxins are insoluble in wax-solvents, and are not 

 volatile. 



He finds also that after the protozoa have been destroyed by 

 heat at 65 deg.-70 deg., the action of volatile disinfectants is to 

 still further increase the bacterial productiveness of the soil. 



Additional indication that these disinfectants act as wax- 

 solvents in dissolving the agricere is afforded by the fact that the 

 upper layers of soils so treated are less nutritive to bacteria than 

 the lower, which is what might be expected if the disinfectant on 

 evaporation carried the agricere to the surface. 



Dr. Gi'eig-Smith is reading a paper before the present section in 

 which he recapitulates his work in this connexion. 



If the theory that the action of heat and of solvents is to 

 destroy the water-proof coating is correct, one would expect that 

 soils so treated would yield more of their mineral ingredients 

 to soil-solvents. The evidence on this point is not conclusive, but 

 it is fairly certain that the increases, when such have been found, 

 are insufficient to account for the great increase in fertility noted 

 by Russell and Hutchinson (three or four times the crop in the 

 case of heat, and 20 to 50 per cent, in the case of volatile anti- 

 septics) . 



S. U. Pickering {Journal Agricultural Science, Vol. 3, p. 32) 

 shows a slight increase in the total water-soluble material both of 

 heated and of treated soils, but the nature of the mineral matter 

 extracted is not stated. 



G. S. Fraps {Jourr.al Ind. and Eng. Chemistry, 3, 335) has 

 found that previous ignition increases the amount of phosphoric 

 acid which can be dissolved from several naturally occurring phos- 

 phates. Wavellite in particular yields ten times as much phos- 

 phoric 'acid soluble in ^ nitric acid after than before ignition. 



It is to be remembered, however, that in this case there is no ques- 

 tion of the presence of agricere, and further, that in our soils, at 

 all events, these minerals are not likely to be present in any quan- 

 tity. 



C. B. Lipman (Journal Ind. and Eng. Chemistry, Vol 4, p. 663) 

 finds in the case of soils the opposite effect to that noted by Fraps in 

 the case of phosphatic minerals. He finds that the effect of igniting 

 soil is to reduce the amount of phosphoric acid extracted by nitric 

 acid. This agrees with the observations of J. Konig and others 

 (Land. Versuch. Stat., 1911, Vol. 75, p. 377-441) that phosphoric 

 acid is fixed by the colloids in the soil, forming insoluble calcium 

 phosphate, and that the combination is rendered more complete by 

 the action of heat. 



H. I. Jensen {Proc. Roy. Soc. N.S.W., Vol. 45, p. 169) has 

 also investigated this point. He treated several soils of varying 

 known degrees of fertility with different soil solvents before and 



