54 
52 5° 
f 'cn / igrade. 
Two separate lots of the mineral were then heated in a similar 
manner to a temperature of 525°C., the melting* point of stibnite, 
a. natural sulphide of antimony. The results obtained were as 
follow : — 
Mineral 
Loss ... 
A. 
B. 
2 
gms. 
0/ 
1 gm. 
0/ 
• 0702 
gms. 
/O 
3-81 
o 
0* 11 
• 0876 
j? 
4-38 
13-01 
• 1632 
j> 
8-16 
13-04 
• 2396 
?? 
1 1 • 98 
• 2513 
9 9 
12-565 
• 2569 
JJ 
12-845 
• 2602 
39 
13-01 
« 2612 
99 
13-06 
• 2616 
99 
13-08 
g was 
gn 
:idual, 
the test being 
withdi 
as soon as the indicator melted, weighed, and reheated to the same 
temperature, the process being repeated until the loss was inap- 
preciable. The test in the second series was allowed to remain in 
the I urnaee several minutes alter the melting of the stibnite. 
I he loss iound in both cases is equal to the total water present 
mid the residue showed practically no loss of SO... The residue was 
partly soluble in water, forming at the same time a sticky gela- 
tinous mass. On warming the water extract a bulky precipitate of 
aluminium hydrate was formed. The equations are: — 
2 [K 2 S0 4 3H0A1S0 4 • 3A1 (OH)*] heated — > 
2K 2 S0 4 + 3 OAl a (S0 4 ) 2 + 3A1 2 0 3 + 12H 2 0. 
I In* theoretical loss to satisfy Ibis reaction is 13.04 per cent. 
On adding water to the roasted product and warming, aluminium 
hydrate is precipitated and potash alum formed in solution. 
3 OAl 2 (S0 4 ) 2 + 3H 2 0 — > 2A1 2 (S0 4 ) 3 -f 2A1 (OH) 3 
Al 2 (S0 4 ) 8 + K 2 S0 4 + 24H 2 0 — > 2KA1 (S0 4 ) 2 - 24H a O. 
The reactions proved by those experiments differ from those 
hitherto accepted. Thus Waggaman* states — 
on heating to a moderate temperature (500° C.) water is driven off and the 
mineral decomposes into alumina and potassium sulphate. 
He makes no mention of the formation of a basic sulphate of alu- 
mina but slates,, inter aha, that, in Italy, for the production of alum 
after calcining the ore at low red heat it is exposed in the air for 
several weeks or months, being moistened with water from time to time 
The reactions are represented thus : — - 
(L) K 2 0 3 A1 2 0 3 4S 0 ;} 6 Ho 0 2KA1 (S0 4 ) 2 + 2Al a 0 3 + 6H a O 
(2.) 2KA1 (S0 4 ) 2 + 24H 2 0 2KA1 (S0 4 ) 2 -24H 2 0. 
* U.S. Dept. Agric. Bull. 415, p. 2, 
