DETERMINATION OF ALKALIES IN MINERALS. 



1. In the examination for alkalies in the class of minerals 

 alluded to in this article it is usual to devote a separate portion 

 of the mineral to their special determination, without having 

 reference to any of the other ingredients contained in the min- 

 eral. This method of proceeding naturally recommends itself, 

 because a fusion with carbonate of soda is so greatly superior 

 for the determination of all other ingredients that even the 

 attempt to control the result of the soda fusion by making use 

 of the one for the alkalies, to arrive at the other substances 

 as well as the alkalies, will in many instances embarrass the 

 analyst as to his results. 



2. It is only in cases of absolute necessity that one portion 

 of the mineral should be used to estimate all its constituents, 

 and this condition of things will be alluded to in another part 

 of this paper, as reference is now had to the quantitative deter- 

 mination of the alkalies, discarding whatever else the mineral 

 may contain. 



3; In the determination of the alkalies in silicates not soluble 

 in acids three important points present themselves: 



I. The means necessary to render the silicate soluble. 



II. The separation of the other ingredients from the alkalies, 

 more especially magnesia. 



III. The removal of the sal ammoniac unavoidably accumu- 

 lated in the process of analysis. 



In all three of these the processes adopted will be found to 

 differ essentially from those now in use, and they are made 

 known only after much experience by the author, in which 

 their advantages have been most fairly tested, comparatively 



* This memoir embraces many important points connected with mineral 

 analysis. The minute practical details for laboratory use are given in another 

 article in this collection of papers, and one written after twenty years' experi- 

 ence with the method. 



