32 



The determination of total phosphoric acid was made,, the 

 method being to weigh out 2 grams of soil into a platinum dish 

 and ignite to drive off organic matter. Put in i or 2 c.c. of 

 hydrofluoric acid and allow the soil to come in contact with the 

 acid slowly to avoid loss by sputtering. After the violent action 

 has ceased, place on a water bath and evaporate to dryness. After 

 repeating this operation once or twice, take up with a little nitric 

 acid and water and determine phosphoric acid. This method 

 was rapid and gave closely agreeing results. In this way the 

 following results were obtained : 



Soil "A." Soil"B." 



Total P 2 5 o. 145% o. 155% 



Complete analyses of the acid soluble materials in these were 

 then made according to the methods of the Association of Official 

 Agricultural Chemists 1 , with the following results : 



DIGESTION IN HYDROCHLORIC ACID 1. 1 15 SP. GR. 



Constituent. Soil "A." Soil "B." 



Insoluble matter 87.85% 83.53% 



Potash (K 2 O) 0.74% 0.80% 



Soda (Na 2 O) 0.20% 0.41% 



Lime (CaO) 0.11% 0.14% 



Magnesia ( MgO) 0.55% 0.78% 



Oxide of Manganese (MnO) 0.03% 0.02% 



Ferric Oxide (Fe 2 O 3 ) i.74% i-9*% 



Alumina (A1 2 O 3 ) 4-oo% 5-72% 



Phosphoric Acid (P 2 O 5 ) 0.12% 0.10% 



Sulphuric Acid (SO 3 ) 0.04% 0.06% 



Carbonic Acid (CO 2 ) 0.26% o.iS% 



Volatile matter 4-*7% 6.51% 



Portions of 200 grams of the air dried soils were then mixed 

 thoroughly with lime (one and two grams), the whole placed in 

 cylinders, moistened and allowed to stand exposed to the atmos- 

 phere for seven days. The portions were then again air dried, 

 and weighed. The solubility of the original and limed portions 



in i per cent citric, and - - hydrochloric acids was then deter- 



200 



i U. S. Dept. Agr. Div. Chem., Bui. No. 46, 72. 



