159 



stitiited for one molecule of Na^, and if, further, the silicic 

 acid and the titanic acid are brought together, the following 



formula is obtained 



Si^ 0^5 Na., , 



to which there is nothing analogous in the mineral kingdom. 

 Neptunite has previously been regarded as the most acidic of 

 all silicates. But narsarsukite is still more acidic. However, 

 this formula may, in accordance with Clarke's view, very well 

 be written thus : 



/[Si^O^Na)^ 



4—SiO^Na 



\SiO. 



>FeF 



xSiO, 



4 — SiO^Na 



Ч (Аг'з Og Na)^ 



If the slight amount of alumina is calculated as ferric 

 oxide, the manganous oxide and the magnesia as soda, and the 

 water as fluorine, and the whole calculated to 100, the relation 

 between the values calculated from the above formula and those 

 found is as follows. 





Calculated 



Found 



SiO^ 



62,36 



61,61 



TiO.^ 



13,79 



14,00 



Fe,0, 



6,88 



6,74 



Na^O 



1 6,03 



16,89 



F 



1,63 



1,32 



100,69 100,56 

 — = F^ 0,59 0,56 



100 100 



Before the blowpipe narsarsukite behaves as follows. In 

 the forceps it fuses readily enough to a somewhat blebby glass, 



