360 Gibson . — On Siliceous Deposit in the 
mineral being what It has always been stated to be, viz. 
silica. 
The amount of silica present In measured lengths of the 
stem was next determined. Portions of stem were dried for 
twenty-four hours over strong sulphuric acid. The dried 
material was then fused over a blowpipe and the weight of ash 
determined. It was found to amount to 9 per cent, of the 
dry weight. 
The ash was then fused over the blowpipe with excess 
of sodium carbonate. The fusion was boiled with water, 
and after the addition of a little hydrochloric acid the whole 
mass was evaporated just to dryness on a water bath. 
Hydrochloric acid was again added, and the mixture taken 
again just to dryness on the water bath. 
Water and a few drops of hydrochloric acid were then 
added, the whole slightly warmed and allowed to stand 
for an hour. The separated Si 0 2 was filtered off and 
weighed. It was found to amount to 30 per cent, of the ash. 
To the hot filtrate, ammonium chloride, ammonium hydrate 
and ammonium oxalate were added. After twenty-four hours 
the precipitate was filtered off, and, to ensure separation of the 
calcium and magnesium, the precipitate was redissolved in 
hydrochloric add preparatory to a second precipitation with 
ammonium oxalate. A small quantity of Si 0 2 (3 per cent, 
of the ash) remained here undissolved. The calcium was 
reprecipitated by ammonium hydrate and ammonium oxalate 
and filtered off after twenty-four hours. The calcium oxalate was 
then transformed into calcium oxide by ignition and weighed 
as such. It was found to amount to 18 per cent, of the ash. 
The filtrate was then treated with ammonium hydrate and 
ammonium phosphate and allowed to stand for forty-eight 
hours. The magnesium was thus precipitated as Mg NH 4 P 0 4 . 
The precipitate was filtered off and the magnesia determined 
from the weight of Mg 2 P 2 0 7 , obtained by heating. It was 
found that the magnesia amounted to 187 per cent, of the ash. 
The other ash constituents were not determined. It may 
be concluded from this analysis that Si 0 2 is taken up by 
