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



given by Rose* (whose name is generally, but incorrectly, given to the 

 method) being merely to use a sufficiently large quantity of the carbo- 

 nate. He admits that a little alumina is dissolved at the same time. 

 Wohlert directs the solution of the two earths to be dropped very 

 gradually with constant stirring into an excess of a warm concentrated 

 solution of carbonate of ammonium, which precipitates the alumina 

 and dissolves the glucina. 



That one extraction with carbonate of ammonium is quite insufficient 

 will be seen from the following experiments and considerations. 



The mixed earths (glucina and alumina) from 2-3217 grammes of the 

 beryl A were precipitated by ammonium hydrate and ammonium sulphide, 

 and allowed to stand all night in a large excess of carbonate of ammo- 

 nium ; the resulting glucina weighed 0-1806 gramme, or only 7*78 per 

 cent, on the beryl, whereas three more extractions raised the p*ercentage 

 of glucina to 11-55 J. 



Agaiu, a mixture was taken of 0*2640 gramme of glucina and 0-8520 

 of alumina, the percentage being : — 



Alumina 76-34 



Glucina 23-66 



100-00 



The mixture was dissolved in hydrochloric acid, neutralized with car- 

 bonate of ammonium, and digested for twenty-four hours with 

 95 cub. centims. of a saturated solution of carbonate of ammonium 

 (sp. gr. 1*080 at 15° C), or 8-5 cub. centims. for each decigramme of the 

 mixed earths. On acidifying the filtered solution with hydrochloric acid, 

 and precipitating with ammonium hydrate and ammonium sulphide, only 

 12*75 per cent, of glucina was obtained instead of 23-66. 



But it might be said that the deficiency in the glucina in the experi- 

 ment quoted arose from the use of an insufficient quantity of carbonate- 

 of -ammonium solution. To settle this point definitely the following 

 experiments were made : — 



Experiment I. — 0-1960 gramme of glucina and 0*1812 gramme of 

 alumina were dissolved in hydrochloric acid, neutralized by ammonia, and 

 treated with 100 cub. centims. of carbonate-of-ammonium solution. This 

 is at the rate of about 27 cub. centims. for each decigramme of the mixed 

 earths. A temperature of 65° 0. was kept up for five and a half hours, 

 the exit-tube of the flask being closed with a mercurial valve. It was 

 found that a pressure of three inches of mercury was sufficient to prevent 

 the escape of vapour at the temperature stated. The solution was 



* Rose's Ohem. Anal. Translated by Normandy, ii. p. 58. 1849. 

 t Handbook of Inorganic Analysis, 1854. 



\ I have much pleasure in acknowledging the skill and accuracy with which some of 

 these fractional extractions were performed by my friend Mr. Raphael Meldola, who 

 was my assistant at that time. 



