DETERMINATION OF ALKALIES IN MINERALS. 219 



occasionally remain behind, we preferred the additional fusion 

 to get at that small quantity, and to entitle it to rank as a 

 method by which all but the merest trace of the alkalies could 

 be extracted from the insoluble silicates. 



59. The proportion of sal ammoniac added to the carbonate 

 of lime as here recommended is arrived at after numerous 

 experiments. By increasing the sal ammoniac, and thereby 

 augmenting the amount of chloride of calcium formed, the 

 mass fuses more thoroughly, but the water does not disinte- 

 grate it as completely as when the ammoniacal salt is less; 

 also the accumulation of this latter at the end of the process 

 is less, an object not to be disregarded. The advantage of thus 

 estimating the alkalies in insoluble silicates is obvious. The 

 long routine of separating silica, alumina, lime, etc., is done 

 away with; the accumulation of chloride of ammonium is very 

 trifling; and lastly, the alkalies are obtained directly in the 

 form of chlorides. The method will vie in accuracy with any 

 other, including the one already mentioned in the first part 

 of this paper; and at the same time it is unequaled in simpli- 

 city, speed of execution, and constancy of results. 



60. In examining for alkalies qualitatively, one fusion will 

 of course be all that is necessary, and the action of the water 

 need not be continued more than thirty minutes before filtering. 

 This method answers even when boracic acid is present in the 

 silicate. The manner of proceeding in such a case will be 

 mentioned in a future paper on the determination of boracic 

 acid in miiferals. 



61. There is nothing new in the attempt to dissolve out the 

 alkalies by water from a silicate that had been heated with 

 lime. M. Fuchs used the method for procuring lithia from 

 lepidolite; but of course his efforts were entirely directed to 

 procuring the lithia from the mineral, and not to estimating 

 its quantity, as the method he followed could not have furnished 

 such results. I have also lately learned that Mr. A. A. Hayes, 

 of Boston, proposed and employed a mixture of chloride of 

 calcium and caustic lime to decompose alkaline silicates, heat- 

 ing over a lamp, and subsequently treating the mass with 

 water to extract the alkalies or chlorides. As little has been 

 heard of this process, I presume the author found it defective. 

 If we are correctly informed, the proportions used were three 



