10 BULLETIN 415, U. S. DEPARTMENT OF AGRICULTURE. 
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. 
(Si0 2 ). 
oxides. 
(KaO). 
(Si0 2 ). 
oxides 
(K 2 0). 
(Fe 2 3 , 
(Fe 2 3 , 
A1 2 3 ). 
AlsOg). 
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, alunite were then heated in an electric 
muffle furnace for a little over an hour at from 550° to 650° C. and 
from 850° to 950° C. Foursamples (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 niters with small successive quantities of hot distilled water 
till the washings gave practically no test for sulphates. The filtrates 
were then analyzed for potash and the efficiency 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 K 2 ex- 
tracted with water after 
ignition at— 
550° to 
650° C. 
750° to 
775° C. 
850° to 
950° C. 
550° to 
650° C. 
750° to 850° to 
775° C. 950° C 
36 
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 
Per cent. 
98.44 
97.23 
93.64 
99.28 
84.99 
91.30 
94.15 
C 1 ) 
64.89 
2 58. 62 
73.17 
Percent. 
100.00 
94.78 
Percent. 
89.49 
35.90 
59.95 
4 
85.20 
5 
6 
28.37 
37.55 
87.28 
100.00 
54.97 
92.17 
55.69 
8... 
92.44 
39.77 
9.50 
72.08 
9 
28.55 
26.86 
33.00 
10 
11 
1 Determination lost. 
2 Traces of feldspathic material found in this sample by Mr. W. n. Fry probably explain the low yields 
of potash on leaching. 
A study of Table II will 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 will be seen that the 
low yield of potash obtained from the highly heated mineral was 
