INJUEIOUS EFFECT OF SULFATE OF AMMONIA. 



121 



be detected by the precipitation test with ammonium hydroxide, it was 

 decided to try larger quantities of soil and larger volumes of water, which 

 would permit subsequent concentration and perhaps yield measurable 

 quantities of these elements by the usual analytical methods. 



Eight kilograms of air-dry soil were put in a percolation jar, the 

 tubulure of wliich was covered with a piece of linen and plugged loosely 

 with glass wool. Enough water was added to saturate the soil, which 

 was then left in the wet condition for two days. Water was then added 

 in portions of 1 liter at a time, each of which ceased dropping from the 

 bottom of the jar before another was added. Eight liters were thus used, 

 and the percolated water was evaporated in a porcelain dish on the water 

 bath until the volume was reduced to 1 liter, which was next filtered 

 tlii'ough paper and finally through a porcelain filter under pressure, as 

 there was a turbidity which paper would not remove. 



The clear soil extract was next heated and made slightly alkahne with 

 ammonium hydroxide. A copious flocculent precipitate formed, which 

 was collected on a filter, washed and then analyzed. When the filtrate 

 was further heated and a few drops of ammonia added, a second precipi- 

 tate, similar to the first, formed and was also analyzed. The two pre- 

 cipitates differed but little in composition, and the results obtained were 

 combined in .Table II. 



Table II. — Constituents of Precipitate obtained in Concentrated Soil Ex- 

 tract, expressed as Milligrams in 100 Grams of Soil. 



The precipitate was found, to contain but a trace of iron, which is not 

 tabulated as such, but is really included in the aluminium oxide. The 

 calcium which separated in the ammonium hydroxide precipitate was 

 apparently in the form of carbonate, as the precipitate from the extract 

 of plot 1 effervesced vigorously when dissolved in hydrochloric acid, as 

 the first step in analysis. 



There is a striking difference between the precipitate obtained in the 

 soil extract from plot 1 and those from plots 6 and 8. The protective 

 effect of nitrate of soda on the calcium in the soil is shown in contrast to 

 the depleting influence of ammonium sulfate, with the consequent forma- 

 tion of salts of manganese and aluminium. No effort was made to esti- 

 mate possible calcium or manganese not precipitated by the successive 

 additions of ammonium hydroxide. 



