rhe 
= 
% 
Atomic Volume of some Minerals. 225 
4, Epidote, Zoisite, Orthite. 
5. The Feldspar family. 
cholzite, Kyanite. 
7. Different groups among the monometric or tesseral species. 
It is not my object in this place to mention the cases of iso- 
morphism that conform to the ordinary law on this subject. 
With this brief enumeration of some of the groups, I proceed to 
the consideration of the atomic volumes of the species. The 
atomic volume is obtained by dividing the atomic weight by the 
specific gravity. 
I present first an example of the atomic volumes of a group of 
acknowledged isomorphous minerals, as a measure of the degree 
of discrepancy to be expected. The carbonates of lime, lime 
nad magnesia, manganese, iron, magnesia, and zinc, increase in 
the angle R:R from 105° 5’ to 107° 40’, and the atomic vol- 
umes, as determined by Kopp, are respectively as follows: 
231-20, 202:36, 202-29, 188-50, 181-25, 175-33. 
The range of numbers is quite wide in this series, amounting to 
4 the larger number, and exceeds what usually occurs among iso- 
morphous species. Yet the extent of the variation, here shown 
to be possible, should be kept in mind, or we may be led into 
error by expecting too close coincidences. 
In the following calculations, either the mean specific gravity, 
as nearly as it could be determined, has been taken, or the specific 
gravity corresponding to some analysis selected for comparison. 
he atomic weights used are from the table on pages 218, 219, of 
fhis volume. By way of distinction as well as brevity in the fol- 
Owing enunciations, we number the statement of the aggregate 
atomic volume by A; that in which the aggregate atomic volume is 
divided by the number of atoms of bases and acid, by B; and that 
of the same divided by the number of atoms of the elements, by C. 
L Chrysoberyl, Chrysolite, Serpentine, Villarsite, Picrosmine, Epsom Salt. 
1 Be=158-084 . atoms of acid and base, 2. ¢. atoms of elements, 7. 
141 641-80 A. 799°884-+3°7 (sp. gr.)=21618 
a. At. weight, 799:884 B, 216:18+2=1089 CO. 216:18-+-7=30°9 
With the old atomic weight of Glucinum, making glucina 96252, we have the 
formula He ‘A16, which gives 
1#e 96252 6. atoms of acid and base, 7. « atoms of elements, 35. 
6Al 38508 A. 4813°324-3°7 (sp. gr.)}=1800°9 
@. At. volume, 4813°32 B. 1300°9-+7==185°8 ©. 1800°9-+-35==3716 
A=433°7; B= 144-6; O—36-14. 
np Series, Vol. IX, No. 26.—March, 1850. 29 
