298 [ FEBRUARY, 
who gave an analysis of it in his *¢ Uebersicht der geol. Verhiltnisse des Herzog- 
thums Nassau ;”? but without calculating its formula. He found that it contains: 
Silicic Acid = 26:45 contains Oxygen = 13°73 2-00 
Alumina 21°25 =o «é 9-93 1-44 
Oxide of iron 44-24 é 6 9°82 
Magnesia 1-06 oS cs 0-41 WE oe 
Water 7°74 G8 $6 6°88 1-00 
100-74 
This ratio leads to the formula: 3(3RO, SiO3)+(3 Al,03, Si03)+-6 HO. 
Breithaupt’s Thuringite is, according to an analysis of Rammelsberg, 3(3RQ, 
Si03) + (2 Fe,03, $i03)-+ 9 HO.* 
These three minerals are therefore: 
Owenite 2(3RO, 8i03)-+ (3R,0,, Si0,)-+6 HO. 
Aphrosiderite 3(3RO, SiO,) + (3Al, O,, SiO,)-+-6 HO. 
Thuringite 3(3RO, Si03)+-(2 Fe, O,, Si0,) + 9 HO. 
The following are the data of Mr. Keyser’s analyses, and the methods used 
for the determination of the different constituents : 
I. 2.0770 Grammes of the mineral gave: 
0.4798 06 Silicie acid. 
1.0865 G Sesquioxide of iron. 
0.3226 H Alumina. 
0.0670 OG Pyrophosphate of magnesia. 
0.0106 cf Carbonate of lime. 
0.0185 G9 Chloride of potassium and sodium. 
0.0033 cs Platinum = 0.0025 chloride of potassium. 
II. 1.2898 <e gave: 
0.4056 G Gold. 
Tee S920 é< gave: 
0.2050 8§=« Water. 
TVie) 121542 GS gave; 
0.1195 US Water. 
V. 1.3668 WG gave: 
0.3187 ¢ Silicic acid. 
0.7148 GL Sesquioxide of iron. 
0.2138 66 Alumina. 
0.0495 GG Pyrophosphate of magnesia. 
0.0105 6c Carbonate of lime. 
I. The finely powdered mineral was dissolved in hydrochloric acid, and silica 
separated in the usual way, with the necessary precautions. In the filtrate the 
oxide of iron was higher oxydized by nitric acid, and sesquioxide of iron and 
alumina precipitated by ammonia; an excess of acetic acid was added to the pre- 
cipitate and repeatedly evaporated to dryness in a water bath. In this manner 
the acetates of iron and alumina were decomposed, and sesquioxide of iron 
and alumina separated from the soluble acetates by filtration. Alumina 
and iron were separated by caustic potash. Lime precipitated from the acetates 
by oxalate of ammonia. The filtrate containing magnesia and alkalies was 
evaporated to dryness, and heated until the ammoniacal salts were expelled; from 
the residue the magnesia was separated from the alkalies by oxide of mercury ; 
the chlorides of alkalies were weighed together and afterwards separated by 
bichloride of platinum. 
II. The mineral was dissolved in hydrochloric acid and cooled, while a 
constant current of carbonic acid passed over it, in order to prevent the oxi- 
dation of oxide of iron by atmospheric air; then a sufficient quantity of ter- 
chloride of gold and sodium was added, and the reduced gold filtered after 24 
*Rammelsberg Handwérterbuch, etc., Supplement III. 
