REMOVAL OF SAL AMMONIAC IN MINERAL 

 ANALYSIS. 



About twenty years ago, in a publication made upon the 

 analysis of the natural silicates, I gave the details of some 

 interesting experiments made upon the removal of sal ammo- 

 niac, which so commonly accumulates in these analyses. 



The method of accomplishing the removal of this salt, being 

 embodied in a lengthy paper embracing many other and more 

 important points, has been to a great extent overlooked by 

 analytical chemists. I have been frequently asked for details 

 in connection with the removal of this salt, and some recent 

 investigations have given me renewed appreciation of the in- 

 valuable nature of the process, where very large quantities of 

 sal ammoniac had accumulated and remained associated with 

 a very minute quantity of material that formed the subject 

 of research. 



It may be of interest to bring this process more clearly to 

 the attention of chemists. The manner of proceeding is as 

 follows: The solution containing the sal ammoniac is concen- 

 trated in a capsule, best over a water-bath or in a glass flask; 

 pure nitric acid is added, about three grammes of it to every 

 gramme of sal ammoniac supposed to exist in the liquid; a little 

 habit will suffice to guide one in adding the nitric acid, as even 

 a large excess has no effect on the accuracy of the analysis. 



The flask or capsule is now warmed very gently, and before 

 it reaches the boiling-point of water a gaseous decomposition 

 will take place with great rapidity. This is caused by the 

 decomposition of the sal ammoniac. It is no advantage to 

 push the decomposition with too great rapidity; a moderately 

 warm place on the sand-bath is well adapted for this purpose. 

 I, however, prefer a porcelain capsule of about three and a half 

 to four inches diameter (in the ordinary operations in mineral 

 analysis), inverting a clean funnel of smaller diameter over it, 



