188 CONTRIBUTIONS TO OUR KNOWLEDGE OF SOIL-FERTILITY, XV: 



Proportion of soil to water, round numbers ... 2:1 1:1 1:2 



Proportion of soil to water, calculated for dry 



soil... ... .. ... ... 1 :0-63 1 :ri7 1 : 2-26 



Reaction to methyl-orange ... ... —0-24 -0-18 i —0-12 



Reaction to phenolphthalein, direct ... -0*044 I -0*016 | -0*008 



Curves of these numbers show that the reaction of the soil- 

 water, equivalent to a ratio of 1 : 0*087 for the dry soil to 8% of 

 moisture, would be between -0*4 and -0-5 for methyl-orange, 

 and about - 0*09 for phenolphthalein; yet the soil was acid to 

 litmus. 



The reaction to phenolphthalein was examined somewhat 

 closely, after the suspicion was raised that the reaction of the 

 solution had more to do with the phenomenon of toxic action 

 than had been supposed to exist. It was found to be untrust- 

 worthy, as much depended upon the rate at which the solutions 

 were boiled, previously to cooling and titration. For example, 

 covered beakers containing 50 c.c. of tap-water were boiled 

 slowly and rapidly, cooled and titrated. 



Much, therefore, depends upon the method and time of boiling 

 in expelling the carbon dioxide. In the tests previously recorded, 

 the extracts were boiled in an open beaker for ten minutes at a 

 speed intermediate between slow and rapid boiling. They pro- 

 bably do not indicate the true alkalinity, but, for that part, it 

 has been shown that the same would have occurred by using 

 methyl-orange. 



A twenty-one-days' culture of bacteria and amcebse was filtered, 

 and the extract treated with lactic acid in decreasing quantities, 

 seeded with tlie test-organism, incubated and counted. It had 

 a reaction to methyl-orange of -01 6°, and to phenolphthalein, 

 direct, of - 004". 



