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



with 100 cub. centims. of a cold solution of carbonate of ammonium, and 

 allowed to stand twelve hours. The glucina was separated in the usual 

 manner. This mode of proceeding was repeated seven times, with the 

 results given in the annexed Table. 



Glucina obtained 

 No. of extractions. (per cent.). 



1 12-75 



II 3-24 



III 0-61 



IV 3-74 



V 1-26 



VI 0-56 



VII 1-13 



23-29 



Composition of Obtained in seven 



mixture. treatments. 



Glucina 23-66 23-29 



Alumina .... 76-34 



100-00 



The alumina was not estimated in this experiment. 



The answer, then, to the question at the head of the section is, that 

 results to within half a per cent, of the truth can be obtained by 

 means of the carbonate-of-ammonium process if a sufficient number of 

 extractions be made. 



4. How do solutions of Glucina and Alumina behave with Carbonate 



of Barium ? 



As it frequently happened, during my analyses of emeralds and beryls, 

 that it would have been a great convenience to be able to precipitate the 

 glucina, alumina, and iron together by means of carbonate of barium, it 

 became necessary to examine the behaviour of the two earths with that re- 

 agent, especially since, as happens so frequently in the literature relating to 

 glucina, there is a difference of opinion among chemists upon the subject. 

 Rose * states that solutions of glucina are not precipitated in the cold ; 

 Fresenius f that carbonate of barium precipitates glucina completely upon 

 cold digestion. This is at variance with the observations of AwdejewJ, 

 who states that only partial precipitation takes place in the cold, but that 

 the precipitation is almost complete on boiling. Joy § endorses Weeren's 

 statement, that both glucina and alumina are precipitated, but does not 

 enter into details. Ordway || states that a solution of nitrate of glucina 



* Handb. d. chem. Anal. ii. p. 61. 

 t Qualitative Analysis, 8th edit. p. 103. 

 | Pogg. Ann. lvi. p. 101. 

 § IjOC. cit. 



|| Sill. Am. J. [2] xxxi. p. 197. 



