216 DETERMINATION OF ALKALIES IN MINERALS. 



47. When the alkalies are presented in the form of chlorides 

 before their quantity has been estimated in some other form it 

 is best to proceed first to the separation of lithia, afterward 

 weigh the chlorides not dissolved by the alcohol-ether, and lastly 

 separate the potash-chloride from the soda-chloride, if both be 

 present, by means of the bichloride of platinum. Experiments 

 were made with a mixture of alcohol and chloroform, the re- 

 sults of which were not as satisfactory as those afforded by the 

 alcohol-ether. 



Substitution of Chloride of Ammonium for Fluoride of 

 Calcium, to mix with Carbonate of Lime to decompose 

 the Silicates. 



48. It was mentioned in the previous paper on this subject 

 how carbonate of lime could be rendered as powerful in its 

 decomposing agency on the silicates as caustic potash, the 

 effect being due to the use of some flux, fluoride and chloride 

 of calcium being used for that purpose. I have since tested 

 more carefully the merits of the chloride of calcium, and for 

 various reasons prefer it to the exclusion of the fluoride. In 

 the first place, it introduces chlorine instead of fluorine into 

 the analysis; and secondly, the fusion is more easily detached 

 from the crucible and dissolved by hydrochloric acid. 



49. The manner of introducing the chloride of calcium into 

 the mixture of mineral and carbonate of lime was a point of 

 some little importance, as from the deliquescent nature of that 

 compound it was inconvenient to weigh and mix it with the 

 carbonate of lime and mineral. These difficulties are obviated 

 by employing chloride of ammonium to form indirectly the 

 chloride of calcium. 



50. The process, which appears to leave hardly any thing to 

 desire, is to take one part of the finely -pulverized mineral, five to 

 six of carbonate of lime, and one half to three fourths of chloride 

 of ammonium* mix them intimately in a glazed mortar, intro- 



* The chloride of ammonium is best obtained in a pulverulent condition 

 by dissolving some of the salt in hot water and evaporating rapidly; the 

 greater portion of the chloride of ammonium will deposit itself in a pulver- 

 ulent condition; the water is poured off, and the salt thrown on bibulous paper 

 allowed to dry ; the final desiccation being carried on in a water-bath, or in 

 any other way with a corresponding temperature. 



