168 Mr. G. Williams on Emeralds and Beryls. [Apr. 26, 



cumstances, dissolves in presence of glucina ; but I shall show further 

 on that the fact does not prevent fairly accurate results being obtained 

 if certain precautions be observed. This tendency of the earths, when 

 mixed, to modify each other's reactions is seen also in their behaviour 

 with carbonate of barium. I have, however, never found the carbonate- 

 of -ammonium process to give too high a number for the glucina, for 

 reasons which are fully discussed further on. 



Hofmeister *, who has made more important and elaborate observa- 

 tions on the carbonate-of-ammonium process than any other chemist, 

 condemns Gmelin's process on the ground that in the treatment with 

 potassium hydrate alumina accompanies the glucinat. He also endorses 

 the statement of Weeren and others, that alumina is soluble in carbo- 

 nate of ammonium in presence of glucina, but shows that this circum- 

 stance is not fatal to the process if a systematic fractional treatment is 

 employed. 



Hofmeister admits that his method is not easy to describe ; and, in 

 fact, it is so operose that the reader must be referred to the original 

 memoir for the details. There can be no doubt that when carefully 

 followed it affords reliable results. I shall endeavour to show further 

 on that the carbonate-of-ammonium process is capable of yielding 

 accurate numbers when employed in a simpler manner. 



From what has been said, it will readily be seen that the two processes 

 I have alluded to are condemned by different experimenters on diame- 

 trically opposite grounds ; and it seems to me that, as is usually the case 

 under such circumstances, the whole question resolves itself into one of 

 manipulation. This being assumed, it became necessary (in order to 

 ascertain the causes of the conflicting statements of the numerous 

 chemists who have subjected emeralds and beryls to analysis) to make a 

 rigorous examination of the behaviour of glucina with solution of car- 

 bonate of ammonium. This has entailed much work, as I have taken 

 most of the statements of the chemists who have worked on the subject 

 and examined them carefully and repeatedly by experiment. 



The following are the principal questions or problems which I have 

 endeavoured to solve : — 



1. Is glucina permanently soluble in a solution of carbonate of am- 



monium ? 



2. Does glucina confer its solubility on alumina ? or does alumina 



confer its insolubility on glucina ? 



3. "With what amount of accuracy can a mixture of glucina and 



alumina be separated by means of carbonate of ammonium ? 



4. How do solutions of glucina and alumina behave with carbonate of 



barium ? 



* Journ. fiir prakt. Cheni. lxxvi. p. 1. 

 t I have confirmed this observation. 



