Issued July 31, 1912. 



United States Department of Agriculture, 



BUREAU OF SOILS CIRCULAR No. 70. 

 MILTON WHITNEY, Chief of Bureau. 



UNITED STATES DEPARTMENT OF AGRICULTURE, 



Washington, D. C., May 21, 1912. 



SIR : I have the honor to transmit herewith the manuscript of an article on 

 Alunite as a Source of Potash, by W. H. Waggaman, Scientist in Fertilizer Re- 

 source Investigations, in this bureau, and to recommend that it be published as 

 Circular 70, of the Bureau of Soils. 



Very respectfully, yX"""^. .*. f<^*xMiLTON WHITNEY, 



OF -ME \ Chief of Bureau. 



Hon. JAMES WILSON, v UN.V* S ,TY 



Secretary of Agriculture. 



ALUNITE AS A SOURCE OF POTASH. 



Alunite is a double sulphate of potassium and aluminum which, 

 on heating, first gives off water and sulphur trioxide, leaving a residue 



FIG. 1. Apparatus for determining the temperature at which the decomposition of alunite 



takes place. 



consisting largely of potash alum. Upon increasing the temperature 



this latter compound decomposes with a further evolution of the 



sides of sulphur, the final residue being chiefly potassium sulphate 



d alumina. 



The alunite used in the experiments was a rather pure sample 

 having the following analysis : 10.86 per cent K 2 O and 30.18 per cent 

 S0 3 . 



In order to determine the temperatures at which the decompositions 

 took place the apparatus shown in figure 1 was constructed. 



50685 Cir. 7012 



