1877.] Mr. Gr. Williams on Emeralds and Beryls. 



175 



is only partially precipitated in the cold by carbonate of barium, a soluble 

 basic nitrate remaining in solution, but that the precipitation is com- 

 pleted on boiling. To study this subject quantitatively I made the fol- 

 lowing experiments. 



Experiment I. — Precipitation of Alumina in the cold by Carbonate 

 of Barium. 



0*8034 gramme of pure alumina was dissolved in hydrochloric acid. 

 The solution was nearly neutralized with carbonate of sodium, and an 

 excess of carbonate of barium, made into a cream with water, was added. 

 After standing twelve hours the precipitate was collected, washed and 

 dissolved in hydrochloric acid. The solution was then boiled and preci- 

 pitated with an excess of sulphuric acid. The sulphate of barium was 

 filtered off with the usual precautions, and the filtrate was precipitated 

 by ammonia. The precipitate was thoroughly washed, dried, and ignited ; 

 it weighed 0*8005 gramme, or 99*64 per cent, on the original alumina. 

 Alumina is therefore completely precipitated in the cold by carbonate of 

 barium. 



Experiment II. — Precipitation of Glucina in the cold by Carbonate 

 of Barium. 



0*5175 gramme of pure glucina were dissolved in hydrochloric acid, 

 and treated precisely as the alumina had been in the last experiment. 

 The precipitate weighed 0*1070 gramme, or 20*68 per cent, on the original 

 glucina. This result, therefore, confirms the observation of Awdejew, 

 that glucina is only imperfectly precipitated by carbonate of barium in 

 the cold, and, under the circumstances indicated, behaves like the nitrate 

 in Ordway's experiments. 



Experiment III. — Precipitation of a mixture of Glucina and Alumina 

 in the cold by Carbonate of Barium. 



0*2096 gramme of pure alumina and 0*2055 of pure glucina were dis- 

 solved in hydrochloric acid and treated precisely like the alumina in Ex- 

 periment I. The precipitate of the mixed earths weighed 0*3874 gramme, 

 or 93*33 per cent, on the original weight. Alumina, therefore, in this 

 case, as in the experiments with carbonate of ammonium, communicates 

 much of its insolubility to the glucina. 



Assuming only the portion precipitated by carbonate of barium to be 

 accounted for in the analysis of a beryl containing 28*89 per cent, of the 

 mixed earths, only 26*96 would be obtained, the loss being 6*67 per cent., 

 which, as we have seen, would fall chiefly upon the glucina, if the opera- 

 tion were conducted in the cold. This loss is, however, variable, and 

 appears to depend, to some extent, upon the relative proportions of the 

 two earths. 



VOL. XXVI. 



