6 BULLETIN 415, U. S. DEPABTMENT OF AGRICULTURE. 
three hours. The ignited mass is then treated with the proper quan- 
tity of sulphuric acid (30° B.) to convert the alumina present into 
sulphate. After standing for some time an amount of potassium sul- 
phate is added sufficient to convert the aluminum sulphate into the 
double salt. The clear liquid is then decanted off and evaporated 
until the potash alum crystallizes out. The reactions on heating to 
800° C. may be represented thus: 
Alunite. 
K 2 0.3A1 2 3 .4S0 3 .6H 2 0= 
Potassium Alumina, 
sulphate. 
Sulphur 
trioxide. 
Water 
K 2 S0 4 + 3A1 2 3 
+ 
3S0 3 + 
6H 2 
J Alumina. Sulphuric acid. Aluminum sulphate. Water. 
2 '13A1 2 3 + 9H 2 S0 4 = 3A1 2 (S0 4 ^ 3 + 9H 2 
Aluminum 
sulphate. 
Potassium 
sulphate. 
Water. 
3A1 2 (S0 4 ) 3 
+ 3K 2 S0 4 + 
Potash alum. 
6 KA1 (S0 4 ) 2 24H 2 
144H 2 0= 
3. 
In the production of alum from the alunite occurring at Bullah 
Delah, Australia, 1 a process similar to that just described is practiced, 
but no particular temperature of ignition is specified and the excess 
of alumina is not converted into alum by the addition of potassium 
sulphate, since it is considered more profitable to manufacture 
aluminum sulphate as a by-product and to produce alum equivalent 
only to the potash present in the alunite. This practice is no doubt 
the best in localities far removed from other sources of potash. 
While it was not the purpose of the present investigation to study 
details of alum manufacture, it would seem that in regions where 
another source of potash is readily and cheaply available a combina- 
tion of the two processes outlined above promises greater possibilities 
than either of the methods employed at present. 
In brief, it is thought that the ignition of alunite at a moderate 
temperature (500° to 550° C.) and subsequent treatment with sul- 
phuric acid and potassium sulphate would mean a saving both in 
fuel and in the quantity of acid required to convert all the alumina 
of the mineral into alum. 
THE PRODUCTION OF POTASH FROM ALUNITE. 
Besides the processes just outlined for the production of alum six 
general schemes have been proposed for the utilization of the potash 
in alunite for other purposes. 
i Pittman, E. P. Alunite in New South Wales. Report Geol. Survey New South Wales (1901). 
