H. B. HuTCHiNsox AXD K. MacLennan 



93 



be much below N/50 strength. The results of a comparative experiment 

 will suffice to illustrate this. 



Initial concentration of solution N/50 N/75 N/100 



Absorption (as per cent, of soil) 0-272 0-2«5 0-210 



Adhering to this period of digestion and N/5() strength of solution the 

 method has been tested against some of those reviewed above, our 

 routine soils being employed. The results of some of these comparisons 

 are given in Table V. 



Table V. Cum.parison of various Methoih for dvkrminmg Soil 



Acidity. 



Where the soil reaction is presumably due to the presence of acid 

 mineral comjDOunds, as in the case of the Woburn soil, the methods 

 proposed by Jones and Hopkins give results closely approaching those 

 obtained by other methods, but this agreement no longer holds when 

 the reaction or lime requirement is due to other causes, as in the Craib- 

 stone soil. It is interesting to note that in both cases the bicarbonate 

 method gives data agreeing well with those from the more laborious 

 Lyon and Bizzell and the Veitch tests. 



In connection with routine bacteriological and chemical work, 

 certain of the above soils had received various additions of calcium 

 oxide and carbonate and served as control material for testing the 

 accuracy of the method. Although the response of a soil to the cor- 

 rection of acid conditions can only be determined generally by carbonate 

 applications, on account of the possible direct chemical action of the 

 oxide on some soils, evidence will be adduced later which tends to show 

 that so long as the neutral point is not reached, the value of oxide for 

 neutralisation purposes is practically the same as that of carbonate. 

 We feel justified therefore in using some of these soils to show the 



