Ki7 



thus allowing the soil to settle before an aliquot part is removed for the 

 determination of the humus. 



The aliquot part is evaporated to dryness, dried at 100° C, weighed, ig- 

 nited, weighed again and the loss reckoned as humus. The following 

 points were under discussion : 



1st. Comparison of Grandeau's method with this modified method. 



I'd. Influence of varying the strength of the ammonia used. 



3d. Influence of varying the time of digestion. 



4th. Is it possible to complete the extraction by Grandeau's method in 

 a reasonable time. 



5th. Comparison of differences in duplicates by each method. 



6th. Are the amounts of phosphoric acid, potash, etc., found in the 

 ash necessarily associated with the humus, as claimed, or are they to be 

 ascribed to the solvent action of the ammonia and to changes due to the 

 absorptive property of the soils. 



Xumerous determinations are given upon seven different soils, showing 

 that the modified method gives much higher results than the ordinary 

 process of Grandeau. 



Second, In the Grandeau method marked irregularities follow the 

 changes in strength of the ammonia solution. These differences in results 

 bear no relation to the strength of the solution used ; they seem to be 

 errors due to the difficulty of securing a complete washing of the soil by 

 the ammonia solution. In the modified method the changes in the 

 strength of the ammonia solution make practically no difference in the 

 amount of the humus extracted, excepting in the case of the peat soil, 

 where 2% ammonia failed to extract all the humus. The results show no 

 considerable increase where the strength is increased above 4 % . The am- 

 monia solutions contained 2, 4, 7.3 and 8% of ammonia. 



Third, The increase of time has not been fully investigated but the 

 results so far obtained indicate that the time exerts less influence in the 

 modified than in the Grandeau method. 



Fourth, .With peat, when the Grandeau method is used, considerable 

 material is passing into solution at the end of ten days ; with ordinary 

 soils this is not the case, but in the case of the black soil (not peat) the 

 extraction was not complete in a week. Oh the peat soil the modified 

 method extracted from f0 to 50 % more than the Grandeau and on ordi- 

 nary soil from two to three times as much humus. 



Fifth, In comparing a large number of duplicates the modified method 



