1877.] Mr. G. Williams on Emeralds and Beryls. 167 



allowed to stand in the cold for fifteen hours longer, and was then 

 filtered. The alumina, after being well washed, dried, and ignited, 

 weighed 0*2089 gramme. 



Composition of Found after one extraction 



mixture. at 65° C. 



Glucina ..51*96 



Alumina ..48*04 55*38 



100*00 



or 7*34 per cent, in excess. 



It was now determined to make one more experiment with double the 

 quantity of carbonate of ammonium used in the last experiment. 



Experiment II. — 0*1945 gramme of glucina and 0*1862 gramme of 

 alumina were dissolved and treated in the cold for twenty hours with 

 200 cub. centims. of the carbonate-of-a.mmonium solution. This was at 

 the rate of 52 cub. centims. for each decigramme of the mixed earths. 



Composition of Found after 



mixture. one extraction. 



Glucina ..51*09 



Alumina . .48*91 55*69 



100*00 



or 6*78 per cent, in excess. 



It is not surprising, therefore, after seeing the results of one extrac- 

 tion under such varied conditions, that Damour *, who tried the carbonate- 

 of-ammonium process in its original form, in his important investigation 

 of chrysoberyl, rejected it in favour of Gmelin's process, on the ground 

 that it failed to extract more than 12 out of the 19*75 per cent, of 

 glucina contained in that mineral. Damour, however, obtained more 

 than 1 per cent, less glucina in proportion than was obtained in the 

 first experiment quoted above. The two results are, nevertheless, 

 remarkably close, and confirm the assertion that one treatment with 

 carbonate of ammonium conducted in the manner described is quite 

 inadequate to extract all the glucina from a mixture of the two earths. 



Joyf, in opposition to Damour, condemns Gmelin's process as giving 

 in his hands too low a percentage of glucina in spite of every precaution. 

 Weereni, who followed Berzelius's method, condemns the carbonate-of- 

 ammonium process on exactly the opposite ground to Damour, namely, 

 because although alumina per se is, he says, insoluble in carbonate of 

 ammonium, it is soluble in the presence of glucina, and thus gives too 

 high a number for the latter. I admit that alumina, under certain cir- 



* Ann. Ch. Phys. [3] vii. p. 173 (1843). 



t American Journal of Science and Arts, xxxvi. p. 83 (1863). This interesting 

 paper contains an invaluable list of memoirs on all subjects connected with the 

 minerals which contain glucina. 



J Pogg. Ann, xcii. p. 91 (1854). 



