28 
CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. [bull.i 
Si0 4 = KH, 
Al — Si0 4 E^Al 
Si0 4 =Al 
Muscovite 
Al- 
Al 
Si0 4 =H 3 
Si0 4 = H 3 
Si0 4 = Al— BO, 
I 
Al — B0 3 ^=H 2 
/Si0 4 = Al— BO, 
- Si0 4 == H 3 
Si0 4 - H 3 
The tourmaline acid. 
Iii the acid, two hydrogen atoms are united with the orthoboi 
group, and twelve with the orthosilicate portion of the nuclei 
Hence, to avoid repetition of the structural expression, the fornin 
may be condensed into a linear form, as follows: 
Al 5 (SiO,)r,(BO,), . B0 3 H 3 . H„, 
and this is applicable to the discussion of the analyses. For examp 
Riggs's analysis of the black magnesium tourmaline from Pierrepoi 
New York, corresponds to the following molecular mixture: 
13. Al5(Si0 4 ) 6 (B0 2 ) 2 
7. Al 5 (Si0 4 )„(BO,), 
2. Al,(Si0 4 ),-,(BO,), 
BO,Ca . Mg 4 H 4 
BO :! Mg . Mg 4 H, 
B0 3 Na, . ALNa 4 H, 
Comparing this with the analysis, and reducing the latter by union 
like bases and recalculation to 100 per cent, we have — 
Found. 
Reduced. 
37.19 
Calculated. 
Si0 2 
35.61 
37.05 
B,0 :5 
10.15 
10.51 
10.80 
A1 2 3 
25.29 
.44 
| 27. 10 
27. 19 
Fe 2 3 
Ti0 2 
.55 
J 
CaO 
3.31 
3.45 
3.40 
FeO.... 
8.19 
I 
MgO 
11.07 
J 16.31 
16.28 
Na,0 
1.51 
1 1.72 
1.74 
K 2 . 
.20 
H 2 
3.34 
) 3.72 
3.54 
F 
.27 
100. 00 
99.93 
100. 00 
The result is evidently satisfactory. In dealing with titanium I ha 
lollowed Penfield, regarding it as really Ti 2 3 and equivalent 
alumina. The fluorine is treated as replacing hydroxyl, and is, thei 
fore, united with the water. It is possible, however, that fluorine m 
