1877.] 



Mr. G. "Williams on Emeralds and Beryls. 



171 



0*5000 gramme of pure alumina was dissolved in hydrochloric acid 

 and precipitated (after neutralization with carbonate of ammonium) with 

 100 cub. centims. of solution of the carbonate. The whole was thrown 

 on a filter at once. The contents of the filter were washed, dried, and 

 ignited. The alumina which had precipitated at once weighed 0*4702 

 gramme. The filtrate, on standing twenty-four hours, had yielded a 

 deposit weighing 0*0281 gramme. These numbers, reduced to percentages, 

 are as follows : — 



Alumina precipitated at once 94*04 



„ coming down afterwards . . 5*62 

 Loss .... *34 



100-00 



It was considered that the question whether glucina confers its solu- 

 bility on alumina would be best answered by treating with carbonate of 

 ammonium a mixture containing a great excess of glucina. 



Experiment I. — A mixture was therefore made of 0-2500 gramme of 

 glucina and 0-0250 gramme of alumina. It was dissolved in hydro- 

 chloric acid, and the excess of acid was removed by evaporation ; 50 cub. 

 centims. of carbonate-of -ammonium solution were then added. The pre- 

 cipitate at first formed entirely redissolved in a few minutes, but the 

 alumina commenced to deposit in about fifteen minutes afterwards. The 

 mixture was allowed to stand for twenty-four hours and was then 

 filtered. The precipitate of alumina containing glucina weighed 0-0323 

 gramme. The glucina recovered from the solution weighed 0*2407 

 gramme ; or, per cent. 



Composition of Found after 



mixture. one extraction. 



Glucina ..90*91 , 87*53 



Alumina . . 9*09 11*75 



100*00 99*28 



The glucina, although in such great excess, had therefore, under the 

 circumstances indicated, not conferred its solubility on the alumina ; but, 

 on the contrary, the alumina had conferred its insolubility on the 

 glucina. 



Experiment II. — The alumina obtained in the manner described was 

 redissolved, reprecipitated, and again treated with 25 cub. centims. of 

 carbonate-of-ammonium solution for twenty -four hours. The glucina 

 had now increased to 0*2432, and the alumina diminished to 0-0298. 

 The composition of the mixture, as found after two extractions, was 

 therefore as follows : — 



