THE RECOVERY OF POTASH FROM ALUNTTE. 9 
author states that this converts the alumina into aluminum fluoride, 
the potassium remaining as sulphate. The product is then leached, 
the potassium dissolving as sulphate, and the aluminum remaining 
in the residue in large part as fluoride. Considerable calcium sul- 
phate remains with the aluminum fluoride, which might necessitate 
changes in the standard process for the electrolytic recovery of 
aluminum. 
TEMPERATURE OF IGNITION AND ITS EFFECT ON THE SUBSEQUENT 
LEACHING OF ALUNITE. 
Of the methods so far proposed for the production of potash from 
alunite, those which depend on simple ignition and subsequent ex- 
traction of the soluble potash with water appear to the writers most 
attractive. 
The following investigation was conducted for the purpose of de- 
determining the best conditions under which a complete extraction 
of the potash could be made from impure as well as the purer grades 
of alunite, with due regard to the production of a salable by-product. 
The investigation involved the study of the effect of ignition at vari- 
ous temperatures, as well as the influence of fineness of division on 
the solubility, or, more correctly speaking, the ease with which the 
mineral yields its potash to hot water. 
Chappell, 1 in discussing the ignition of and subsequent extraction 
of potash from alunite, states that the temperature may be carried 
over 1,000° C. without causing the formation of potassium aluminate, 
and recommends a temperature of from 800° to 1,000° C. for alunites 
containing from 1 to 2 per cent of silica. The experience of the 
writers has been, as shown below, that in igniting alunite containing 
even small quantities of silica, 800° C. should be the maximum 
temperature allowed in the furnace. 
Eleven samples of light-colored alunite from the deposits north 
of Marysvale, Utah, were employed in these experiments. Most of 
the samples were ground to pass a 100-mesh sieve, though it was later 
shown that this was probably unnecessary. The material ranged in 
potash content from 3.48 to 9.61 per cent and in silica from 1.67 to 
39.93 per cent. 
The potash content of the samples was determined by the J. Law- 
rence Smith method, 2 and silica and alumina were also determined in 
all the samples. The results of these analyses are given in Table I. 
i U. S. Patent No. 1070324 (1913). 
2 In order to avoid an excess of sulphates, the samples after being weighed out were ignited at a bright 
red heat before mixing with the ammonium chloride-calcium carbonate mixture. 
