10 BULLETIlSr 415;, U. S. DEPAKTMEISTT OF AGEICULTUEE. 



Table I. — Analyses of samples of light-colored alunite from the Marysvale area, Utah. 







Iron and 









Iron and 









alumi- 









alumi- 





Sample 



Silica 



num 



Potash 



Sample 

 number. 



Silica 



num 



Potash 



number. 



(SiOs). 



oxides. 



(K2O). 



(Si02). 



oxides 



(K2O). 







(FesOs, 









(Fe203, 









AI2O3). 









AI0O3). 







Per cent. 



Per cent. 



Per cent. 





Per cent. 



Per cent. 



Per cent. 



1 



4.41 



36.10 



9.61 



7 



39.93 



23.17 



5.64 



2 



16.98 



35.96 



6.13 



8 



1.67 



37.38 



8.60 



36 



16.66 



34.30 



7.24 



9 



35.93 



25.82 



4.30 



4 



29.14 



27.06 



6.89 



10 



39.20 



26.97 



3.48 



5 



27.50 



28.49 



6.13 



11 



22.08 



30.16 



6.41 



6 



5.90 



36.71 



8.20 











Two-gram samples of each almiite were then heated in an electric 

 mu.ffle furnace for a Httle over an hour at from 550° to 650° C. and 

 from 850° to 950° C. Four samples (Nos. 1, 2, 5, and 6) were heated 

 to a temperature midway between these two extremes^ namely, 750° 

 to 775° C. 



The loss on ignition was determined and the residues then washed 

 on the filters with small successive quantities of hot distilled water 

 tiU the washings gave practically no test for sulphates. The filtrates 

 were then analyzed for potash and the eflSciency of the extraction 

 thus determined. The results of these experiments are given in 

 Table II. 



Table II. — Loss on ignition and percentage of potash extracted from alunite after heating 



at various temperatures. 



Sample number. 



Loss on ignition at— 



Proportion of total K2O ex- 

 tracted with water after 

 ignition at— 





550° to 

 650° C. 



750° to 

 775° C. 



850° to 

 950° C. 



550° to 

 650° e. 



750° to 

 775° C. 



850° to 

 950° C. 



1 



Per cent. 

 14.50 

 20.30 

 21.71 

 15.01 

 12.44 

 22.18 

 14.18 

 16.13 

 14.26 

 14.54 

 16. 71 



Per cent. 

 37.71 

 32.37 



Per cent. 

 39.55 

 35.81 

 35.35 

 29.43 

 31.04 

 39.09 

 26.41 

 41.93 

 28.55 

 26.86 

 33.00 



Per cent. 

 98.44 

 97.23 

 93.64 

 99.28 

 84.99 

 91.30 

 94.15 

 (0 



64.89 



2 58.62 



73.17 



Per cent. 

 100.00 

 94.78 



Per cent. 

 89.49 



2 



35.90 



36 



59.95 



4 







85.20 



5 



28.37 

 37.55 



87.28 

 100.00 



54.97 



6 



92.17 





55.69 



8 







92.44 



9 







39.77 



10 







9.50 



11 r 







72.08 











1 Determination lost. 



2 Traces of feldspathic material found ia this sample by Mr. W. H. Fry probably explain the low yields 

 of potash on leaching. 



A study of Table II wiU show that the extraction of potash by 

 water from the alunite heated at a relatively low temperature (550° 

 to 650° C.) was much more complete than from those samples heated 

 to 850° C. or above. By referring to Table I it wiU. be seen that the 

 low yield of potash obtained from the highly heated mineral was 



