Analyses of Phlogopite. 385 
The fluorine, however, comes in as an important element, and 
one which it is somewhat difficult to dispose > Bt: in a perfectly 
satisfactory manner. 
. Rose considers the fluorine to exist as ioctl of potassium, 
and gives the formula K FI+(3R* Si+28 $i) This corresponds” to - 
the ratio 3 ; 2 : 5—the potash being removed from the other aii 
eve as a fluo 
rid. ane 
bedlatiors remarks that the fluorine may be considered as © 
Rilicotiuorid of potassium ; but Rose is opposed to this view, on. 
the ground that it would. ‘change the ratio of the oxygen in the _ 
several oxyds. This it would do, if it were considered simply-as 
silicofluorid of potassium, but if, in accordance with the recent — % 
views of aarerneiiet published in his last supplement, it is. 
taken as replacing oxygen in the several compounds, the ratio. 
will remain tind ened In this view, the formula 7R* Si+-4a1 Si, 
represents correctly the constitution of the mineral, if we supp 
the oxygen partly replaced by fluorine 
€ apportionment of the fluorine and oxygen to the several ty 
eee is as follows :— 
1. Meitzendorff’s Mica 
Oxyg' 
ee es Fluorine 2 en in sha Sum. 
Combined with Si 165 Si 20°68 22:33" 
¥ ¥ 
Al 060 Als 6-92) 148 8-05 
a ape He 0535 
Mg 0°90 Mg 10-94 
K 015 ‘ 158 12°68 13°73 
Na 016 
Ratio Lf 22: 278. 
Eee 2. Mica from Edwards. Analysis 1, 
Fluorine a ore in residues. Sum. 
Combined with si 2-101 Si 997 22-071 
0764 Al pi 8554 
ie 1146 Mg 1056 
K  ot91 K 1-71 + 12°43 18-767 
Na = 016 
Ratio =1:6: 1 : 2:58. 
The ratio of the silico-fluorids to the silicates is 1: 30 in Meit- 
zendorff’s analysis, and about 1: 24 in the mica oft 3 
according to the first, the detailed formula is— . 
30(7R? Si+41 Si]+1[7(3R F-+Si F*)44(Al F*+Si F?)] 
and according to the second— 
o4[7R? Bi444l Si]4-1[7(3R F-+Si F*)+4(Al F*-+48i FS)], 
Analyses 2 and 3 correspond closely with Meitzendorff’s 
the ratio, if this view of the fluorine be taken, and the aids 
3 with fluorine and those without, which are alike _o 
come range one general Sere a. 
Srconp Serres, Vol. X, No. 30.—Nov., 1850. © 49 
