potassium sulphate and the associated silica and silicates. The re- 
sults obtained were: — 
Calcined at Calcined at 
801° C. 960° C. 
0 / 0 / 
Ignition loss ... ... ... ... ... 29-08 30*54 
Water soluble Potash, K 2 0 ... ... ... 4-02 3-70 
Water soluble Soda. Na 2 Q ... ... ... 2-49 2-22 
The increased ignition loss in this ease is due to the dissociation of 
the potassium and sodium sulphates. 
SOLUBILITY OF ALUNITE. 
The production of water soluble potash from alunite for fertil- 
ising purposes by roasting* bas proved to be a fairly costly process, 
entailing* the employment of an extensive roasting* plant. The fuel 
consumption has been found to be excessive owing' to the fact that 
the reactions taking* place are endothermic ; and the necessity of 
keeping* the temperature within comparatively narrow limits is a 
severe tax on the staff. 
Owing* to the fact that very little information was obtainable 
showing* the solubility of the mineral in various reagents, the fol- 
lowing experiments were carried out with a view to ascertaining 
if some cheaper method could be evolved for rendering the potash 
available as a plant food. 
SOLUBILITY IN WATER. 
The only direct references to the effect of water upon alunite 
which could be found were those of Waggaman and Cullen* 
and of Janes,! who both say that alunite is “insoluble in water/’ 
In view, however, of the rapid solution of alunite by caustic 
alkali solution, it appeared probable that its solubility in pure water 
was appreciable. 
The material chosen for this test was soft and porous, Tt 
was over 09 per cent, pure, containing ICO, 7.5(3 per cent; Na 2 0, 
2.56 per cent.; the impurities being quartz with traces of kaolin, 
muscovite, limonite, epsomite and common salt. 
This material was crushed to pass a 30-mesh sieve, the major 
part passing also a 00-mesh sieve. One gramme was placed in a 
silica beaker, covered with 100 cc. water and stirred at frequent 
intervals with a platinum rod. At the end of one day the solu- 
tion was decanted through a small dense filter and the filtrate) 
evaporated to dryness in a weighed platinum dish, dried at 200° C. 
and weighed. Thereafter the process was repeated four times, the 
length of standing being increased to two days, but the same gramme 
of ore and (lie same filter was used throughout. The temperature 
ranged from 15° C, to 25° C., an average of 20° C. Owing to 
the tendency of much of the finest alunite to float on the surface 
of the water, there should be no doubt as to the saturation of the 
* U.S. Dept., A^rie. Bull. 415, p. 2. 
t Comm, of Aust., Adv Gonna of Sci. and Ind., Bull. No. 3, p. 9. 
