378 The Flocculation of Soils. Ill 



Clearly therefore the sohibility of the acid-salt-forming bases is in- 

 creased by ignition to a much greater extent than the neutral-salt-forming 

 bases. Indeed the neutral-salt-forming bases dissolve to a less extent 

 after ignition of the original subsoils. 



2. The thiocyanate test was appUed to a number of soils before and 

 after a partial ignition. Soils containing excessive amounts of organic 

 matter or of chalk showed no reaction with alcohoUc thiocyanate after 

 ignition, but with 30 mineral soils taken at random the reaction with 

 thiocyanate was increased. Those soils which gave no colour before 

 ignition did so after, and those which gave a colour before ignition gave 

 a much more intense colour after. 



3. The effect of partial ignition on the base absorbing power, as 

 measured by the Hutcliinson-McLennan "Hme requirement" method, 

 was examined in a number of experiments. Two 20 gm. portions of each 

 sample were weighed out and one portion ignited over a bunsen flame 

 for 5 minutes. "Lime requirement" determinations were then made on 

 the original and on the partially ignited portions. The results are shown 

 in Table IV. 



Table IV. 



The effect of 5 minutes' ignition on tlie "lime requirement" of soils 



and subsoils. 



(CaCOs per 100 of Soil.) 



* The concentration of the bicarbonate solution was increased. 



Normal soils showed a lower base absorbing power after partial 

 ignition and this effect was very much greater when much organic 

 matter was present. Subsoils containing no organic matter .showed a 

 greater base absorbing power after partial ignition. The same subsoils, 

 however, after extraction with dilute acid showed a lower base absorbing 

 power. 



4. A number of experiments were carried out with pure substances 

 in search for some synthetic system of known constitution which also 



