REMARKS ON THE ALKALIES 



CONTAINED IN THE MINEEAL LEUCITE AND ON THE COM- 

 POSITION OF WAKWICKITE. 



In examining recently many of the silicates containing 

 alkalies my attention has been called to leucite, and it is on 

 that mineral especially that I would now remark, reserving for 

 another time my observations on the other silicates. 



The specimens of leucite examined came from four localities. 



Vesuvius, Andernach, Borghetta, and Frescati. They were 



about as good specimens as are obtained from those localities. 



although all of them were not equally pure. The alkalies 



found in each calculated as potash were 



Vesuvius 21.85 



Andernach 20.06 



Borghetta 20.68 



Frescati 20.38 



The specimen from Andernach was analyzed for the silica, 

 etc., and found to contain silica 54.75, alumina 23.08, and 1.55 

 of oxide of iron; this last seemed to be mechanically dissemi- 

 nated through the crystals. 



I say above in relation to the alkalies " all calculated as pot- 

 ash," for the reason that there is a notable quantity of rubidium 

 and caesium present in all the specimens above mentioned. In 

 fact, by the method adopted in testing for these alkalies, abun- 

 dant indications are obtained of the presence of rubidium and 

 csesium (the last not so readily) even when operating on but 

 half a gramme of the mineral. I am now engaged in working 

 out a method of estimating quantitatively rubidium and caesium 

 in the presence of other alkalies ; by this method, not yet 

 perfected, the quantity of these alkalies in leucite is found to 

 be about nine tenths of one per cent, of the entire mineral. 



Of course it is not at all remarkable that the potash in the 

 different specimens of leucite should be the same; but it is a 



