DETERMINATION OF ALKALIES IN SILICATES 



BY IGNITION WITH CAKBONATE OF LIME AND 

 SAL AMMONIAC. 



In the following description of a method of separating and de- 

 termining the alkalies I aim to give the minutest details, and it is to 

 be regarded as an appendix to the one on page 200. Numerous 

 analyses have given me the experience here presented ; and I 

 am convinced that analytical chemists, if they follow out the 

 directions, will not resort to any other known method. If there 

 be a better method, it is yet to be discovered. The presence of 

 boracic, hydrofluoric, and phosphoric acids in the minerals in 

 no way interferes with the process. Even in silicates soluble in 

 acids I prefer this method, in common with other analysts, for 

 its ease and accuracy. I made the researches during the latter 

 part of 1852, and the details were published early in 1853 * 

 Since then I have employed the process many hundreds of times 

 with the most accurate results. Some minor points were not 

 completed satisfactorily until several years after the first notice 

 of the method; these have since been perfected, and I now 

 know of nothing further that is needed. 



The purpose of this article is to give all the improvements, 

 with a minute detail of the manipulations and of the precau- 

 tions necessary, all of which are simple and easily executed. 

 In the two articles on the subject of alkali determination in 

 minerals, published in 1853, the whole subject was reviewed, 

 and it is needless to return to it now. I then considered the 

 processes by caustic baryta and its salts, and by hydrofluoric 

 acid, and also detailed some experiments on the separation 



* Shortly after my first publication in this country M. St. Claire Deville 

 made known his method of analyzing the silicates by fusion with carbonate 

 of lime, but the nature of his process and the objects to be arrived at were 

 quite different from those attained in this process. 



