1877.] Mr. G. Williams on Emeralds and Beryls. 169 



I. Is Glucina permanently soluble in a solution of Carbonate of Ammonium'? 



This question is of paramount importance, because if glucina once 

 dissolved in carbonate of ammonium is liable to assume an insoluble con- 

 dition and separate from the solution, it introduces a complication into 

 the process, the effect of which it is difficult' to estimate. The only- 

 chemist, as far as I am aware, who asserts that glucina separates out 

 under the circumstances named is Joy*, who states that " If the solu- 

 tion be kept longer than ten days a precipitate of carbonate of glucina 

 will begin to form, and at the expiration of sixteen days 15 per cent, 

 less of the original amount will go (sic) into solution." This assertion 

 of Joy's caused me some perplexity at first, as I had during many years 

 repeatedly dissolved glucina in solution of carbonate of ammonium, but 

 I had never observed a deposit to take place unless I had reason to sus- 

 pect the presence of alumina. I therefore resolved to submit pure glucina 

 and mixtures of that earth with alumina to repeated quantitative ex- 

 periments, with the view of deciding the question. 



Experiment ■ I. — 0*6943 gramme of glucina, which had already been 

 partially purified by solution in carbonate of ammonium, was dissolved 

 in hydrochloric acid ; ammonium hydrate was then dropped in until the 

 solution was very nearly neutral, and 138 cub. centims. of solution of 

 carbonate of ammonium were added t. At first nearly every thing was 

 dissolved, but a precipitate soon commenced to form. This is quite 

 characteristic of the presence of alumina. The solution was filtered next 

 day, and the precipitate was collected, washed, dried, and burnt with all 

 the usual precautions. The weight of the alumina was 0*0058 gramme, 

 or 0*84 per cent, on the glucina taken. The solution was put aside in a 

 well- stoppered bottle, as I intended to filter it in sixteen days ; but as 

 much more than that time passed without a precipitate forming, it was 

 put carefully away for three years. At the end of this time the bottle, 

 on being shaken, showed a barely perceptible trace of deposit ; neverthe- 

 less it was filtered off with every precaution and was found to weigh 

 0-0038 gramme, or 0-55 per cent. ; and this, was probably partly alumina 

 and partly silicate, arising from a slight decomposition which had taken 

 place of the glass of the bottle. 



Experiment II. — 0*2140 gramme of the glucina which had remained 

 three years in solution was next experimented on. The, earth was dis- 

 solved and treated as before with 50 cub. centims. of carbonate-of-ammo- 

 nium solution. In ten minutes after being well agitated all but a few 

 imponderable flocks were dissolved. In fifty minutes they were scarcely 

 visible. Two days after, they had totally disappeared. In 16 days, the 

 period at which Joy says 15 per cent, less of the glucina will remain in 

 solution, the liquid was filtered and yielded 0*0023 gramme of precipi- 



* Loc. cit. p. 89. 



t The solution of carbonate of ammonium used in these experiments was always 

 of the same strength, i. e, a cold saturated solution, sp. gr. 1*080, 



