EFFECT OF SULFATE OF AMMONIA ON SOIL. 



81 



the concentration of the ammonium-sulfate sohition used, was noticed. 

 The largest amount was removed from one of the ammonium-sulfate 

 plots, — No. 8. 



Table VI. — Milligrams of Iron Oxide removed from 100 Grams of Air- 

 dried Soil by Different Solutions of Ammonium Sidfate. 



Plot. 



N Solution. 



1 UL, 



6 UL. 



7 UL, 



8 UL, 



.51 



.50 



1.02 



Table VII. — Milligrams of Iron and Aluminium Oxides removed from 100 

 Grams of Air-dried Soil by Different Solutions of Ammonium Sulfate. 



Plot. 



N Solution. 



2}2 N Solution. 5 N Solution 



1 UL, 



6 UL, 



7 UL, 



8 UL, 



6 L, . 



None. 



12.00 



2.00 



1.50 



None. 



4.25 

 12.00 

 8.00 

 7.75 

 2.50 



6.50 

 33.00 



7.50 

 28.00 



8.00 



The most striking difference is in the much larger amomit removed from 

 the ammonium-sulfate plot 6 UL. 



In trying to purify the precipitates it was found that thej' contained 

 silica as well as the oxides of iron and alumina. 



In order to determine if these precipitates had the same com- 

 position in all cases, or varied with the concentration of the solvent used, 

 extracts with different strengths of ammonium-sulfate solutions were 

 made with soil from the unlimed end of plot 6. One-tenth normal, one- 

 half normal and normal concentrations of ammonium-sulfate solutions 

 were employed and the extracts made in the usual way. On addition of 

 ammonium hydrate to the extracts a flocculent precipitate formed, which, 

 after being dried and ignited, proved to have the following approximate 

 composition : — 



Oxides of iron and aluzninium, 

 Silica, .... 



Per Cent. 

 . 75 

 . 25 



The precipitates from the different strengths of ammoniiun-sulfate so- 

 lution all had about the same composition. Attempts made to obtain this 



