52 
Boiling' for a few minutes with a mixture of one part of 22 E 
hydrofluoric acid and two parts of 10 E sulphuric acid gave a per- 
fect solution. This was found a convenient method of solution for 
the estimation of ferrous iron. 
Digestion of the powdered .mmeral with weak caustic potash 
(IE) in the cold (18° C) resulted in somewhat slow decomposition. 
The colour of the powder had changed after five minutes from 
yellow to orange, and after 30 minutes to light red, the colour 
gradually deepening. Contact with alkali of the same strength at a 
temperature of 50° C resulted in rapid decomposition, all S0 3 and 
Na.O going into solution and leaving a bulky dark red residue of 
ferric hydrate. The instability of the mineral towards moderately 
concentrated alkalis is further illustrated by the fact that if a slight 
excess of ammonia or fixed alkali is added to a solution of the 
mineral in hydrochloric acid, the resulting iron precipitate contains 
no trace of either sulphuric oxide or alkali. 
At the suggestion of Mr. Alex. Montgomery experiments were 
made on the effect of the mineral on weak potassium cyanide solu- 
tion, 0.2 gm. of the powdered mineral was digested in the cold with 
50 cc. of a 0.5 per cent, solution of potassium cyanide. After 1 % 
hours no weakening of the solution was determinable, after two 
days, however, the strength of the solution was reduced by 10 per 
cent. This fact has an obvious bearing on the problem of successful 
extraction of gold from oxidised ores, in which this mineral, or a 
similar one, may be present without having been detected. 
Effect of dry heat. — On heating the mineral for an hour at 
100°, a minute loss (0.01 to 0.04 per cent.) of hygroscopic water 
was noted. Further successive heatings for an hour each time with 
rises of 10° up to 150° caused no further alteration in weight what- 
ever. None of the water, therefore, is water of crystallisation. At 
a temperature below red heat, acid water was evolved and at a very 
low red heat fumes of SO :i were observed to come off. On heating 
over a meeker burner in a platinum crucible, practically constant 
weights were reached with a loss of 35.36 and 35.50 per cent. This 
is equal to all the water plus three-quarters of the sulphuric oxide. 
Cold water extracted sodium sulphate from this ignited mineral, the 
residue being practically pure ferric oxide. Blasting produced a 
slow reduction in weight, doubtless due to dissociation of the alkali 
sulphate. After 30 minutes it amounted only to 0-8 per cent., after 
which the process was discontinued. 
On heating a small fragment of the mineral in an open bunsen 
flame an intense soda coloration was produced. 
Heating in a closed tube gives white fumes which condense to 
a strongly acid sublimate of sulphuric acid and water, leaving a dark 
red residue. 
