PAPERS OX CHEMISTRY AND PHYSICS 313 



The general procedure of the experiment was as fol- 

 lows: 25 grams of mineral soil or 12.5 grams of organic 

 soil (peat) were placed in a 350 c. c. glass bottle, thor- 

 oughly mixed with a given amount of fertilizing mater- 

 ial, moistened with distilled water, and let stand for seven 

 days at room temperature. At the end of this period, it 

 was taken with 250 c. c. of fifth normal nitric acid and 

 shaken for three hours in a shaking machine. Then it 

 was filtered on a dry filter paper. 200 c. c. aliquot of 

 clear solution was taken for determination of phos- 

 phorus. Volumetric method of analysis was followed in 

 this work. The average of two determinations is given 

 in the tables. 



It is recommended often in the studies of weak acid ex- 

 tractions to make the acids somewhat stronger than 

 fifth normal so that after the soil bases are neutralized 

 the remaining acidity will be equal to fifth normal. Such 

 an arrangement, of course, would give the phosphatic 

 compounds in different soils the same chance for equal 

 solubility. This procedure, however, introduces a very 

 objectionable feature for the comparative study of diff- 

 erent soils. The solvent necessarily would be different 

 for nearly every soil, and the results could hardly be com- 

 parable. It seems as though we should accept soils as 

 such : accept the conditions under which any given soil 

 has to function, and make our observations, preserving 

 these conditions intact. 



If we take two field soils and subject them to the same 

 cultural and climatic conditions, we may safely expect 

 the resultant soil solutions to be practically the same. 

 Yet the ultimate character of these two soil solutions may 

 be widely different depending on the physical and chemi- 

 cal character of these respectiYe soils. 



There are given two soils : one is abundantly supplied 

 with carbonates, while the other is very deficient in them. 

 The solvent action of acids formed in the soils will go 

 very largely to neutralize the carbonates in the first soil, 

 and will be available as a free acid in the second soil. 

 Naturally there will be more phosphorus available for 

 crops in the second soil than in the first. The field ob- 

 servations at various experiment stations show that soils 



