Nov. II. 191S Soil Acidity as Affected by Moisture Conditions 



325 



Table III — Soluble oxids in normal potassium-nitrate extract of soils with changes 



due to drying 



[Results expressed as grams of oxids per 100 cc. of extract from acidity determinations] 



There was a great difference in the amounts of manganese found in 

 some of the soils. The manganese, like the iron, appears to have been 

 very largely reduced and made soluble by saturating the soil with water 

 and excluding the air. In soils A and C over one-half the total soil 

 manganese was dissolved by the potassium-nitrate solution. Unlike 

 iron, the manganese did not rapidly oxidize upon air-drying the soil. 

 Undoubtedly, under proper conditions, oxidation of manganese takes 

 place, although much less rapidly than that of iron. In view of the 

 wide variations between the manganese results, new solutions were 

 prepared, and the gravimetric determinations were checked and con- 

 firmed by means of the Volhard volumetric and the lead-peroxid colori- 

 metric methods. 



