40 



quantities of alkali metals. This composition may be denoted 

 by the following structural formula: 



F 



Ce-0 

 -^0 



С 

 0^ ^0 



Ca 



0-C 

 0^ 



For the mineral from Muso the formula would be some- 

 what more complicated, viz. 



Ce.J\CaC.,0,, 

 the structural formula being as follows: 







C—0~C—0—C 



Л Л Л 



F 00 00 00 F 



\ I / V \ I / 



Ce Ca Ce 



The values found by Dam о ur and De vi lie do not, how- 

 ever, quite correspond to the latter formula. The quantity of 

 fluorine indicated is too small. Further, the analysis shows a 

 loss of 1 per cent. If this loss is assumed to be fluorine (or 

 hydroxyl), the agreement with the proposed formula is somewhat 

 better. The difference in composition between the two minerals 

 would then lie in the fact that the Narsarsuk mineral consists 

 of equivalent quantities of fluorcarbonate of earths and of cal- 

 cium carbonate, while in the mineral from Muso these sub- 

 stances are presumed to enter in the proportion of 2 to I. 



In the foregoing it has been stated that the two minerals 

 differ from each other with regard to several of their most 

 important characters. To facilitate the comparison these cha- 

 racters are collected together in the following table. 



