solution under these conditions. The weight of the extractions 
was corrected by a blank on the distilled water used. Owing to 
the fact that this contained a little organic matter the final weigh- 
ings were made after heating to a temperature of about 400° (\, 
which was sufficient to drive off this organic matter and dehydrate 
the alunite taken into solution. The first extract (0.0048 gin.) 
contained the greater part of the associated epsomite and salt. 
The second extract contained a little, and the third probably traces, 
but Hie fourth and fifth should not have been contaminated. The 
solubilities shown by these two were, in. 100 cc. 
4th 0.0003 grammes. 
5th 0.0-0025 „ 
The mean solubility, therefore, of alunite in 100 cc. of pure water at 
20° C. is 0.00027 grammes. 
This is of the same order as that of barite (BaSQJ, which is 
0.00023 grammes. 
SOLUBILITY I S' CAUSTIC ALKALIS. 
No mention is made by Dana and Lecroix, two well recognised 
authorities on mineralogy, of the effect of solutions of KOH and 
NaOH upon alunite. Janes'* says “It is readily soluble in caustic 
alkalis*” 
The material used in these experiments was 00 per cent pure, 
containing 7.50 per cent. K.,0 and 2.50 Na 2 G, the impurities being 
a little quartz., kaolin, and water soluble sulphates. 
One half gramme lots of the mineral were treated with dif- 
ferent strengths of NaOH solution for varying lengths of time 
and at different temperatures* being stirred well from time to time. 
The solutions were then filtered and washed well with hot water; 
the filtrates were just acidified with hydrochloric acid, boiled to 
expel any OO., present, then sufficient barium chloride added and 
the solutions allowed to stand for a few hours. The barium sul- 
phate was filtered off and weighed and calculated as SO... 
The SO, was determined in a blank on the reagents used and the 
SO., found plus the water soluble sulphates present in the mineral 
deducted from the total. The SO, dissolved was then calculated as 
alunite from a factor found by determining tbe total insoluble SO., 
in tlie sample. The figures obtained were as follow:— 
1 per cent. XaOII Solution. 
Alunite 
Sodium 
Solution. 
Tempera- 
Time. 
Alunite 
taken. 
in 
ture. 
dissolved, 
Solution. 
cc. 
0 
■n 
0 * feta. 
0-2875 
50 
20° C. 
2 hrs. 
19-2 
0 * 5gm. 
0-2875 
50 
20° C. 
4 hrs. 
30-4 
O' 5gm. 
0-2875 
50 
91° C. 
2 hrs. 
98-6 
per cent. 
XaOII Solution. 
0* 5gm. 
1 • 4375 
50 
20° C. 
2 hrs. 
84-3 
0-5gm. 
1-4375 
50 
91° C. 
20 mins. 
1 00-0 
* Comm, of A ust., Adv. Comic, of Sci. and Ind„ Bull. No. 8. 
