EFFECT OF SULFATE OF AMMONIA ON SOIL. 



81 



the concentration of the ammonium-sulfate solution 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 Sulfate. 



Plot. 



N Solution. 



1 UL. 



6 UL, 



7 UL, 



8 UL. 



.51 



.50 



1.02 



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

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



Plot. 



1 UL, 



6 UL, 



7 UL, 



8 UL, 

 6 L, . 



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

 the ammoniimi-sulfate plot 6 UL. 



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

 siUca 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-suKate solutions were 

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

 half normal and normal concentrations of ammonium-suffate solutions 

 were employed and the extracts made in the usual wa3^ On addition of 

 ammonimn 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 aluminium, 

 Silica, .... 



Per Cent. 

 . 75 

 . 25 



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

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



