C. A. Joy on Glucinum and its Compounds. 89 
ren’ as preferable to any other. My observations confirm the 
accuracy of the results to be obtained, if all of the precautions 
are observed, but the time required for the digestion of the mix- 
ture and the care to keep it at a proper concentration render it 
more tedious than other methods, without a corresponding in- 
crease in the yield of glucina. 
2. By carbonate of ammonia.—The filtrate from the silica was 
dropped, with constant stirring, into a warm concentrated solu- 
tion of carbonate of ammonia in excess, which precipitated the 
alumina and dissolved the glucina. The solution was left for 
some days in a corked flask, and occasionally well shaken. After 
separating the alumina by filtration, the glucina was obtained 
by distilling off the carbonate of ammonia and collecting on a 
filte e carbonate of ammonia was thus saved for future 
operations. A serious objection to this method is the fact that 
considerable alumina is always dissolved in the presence of glu- 
cina, although alone it is not affected by carbonate of ammonia. 
I instituted a series of experiments in order to ascertain the de- 
~ of concentration of the carbonate of ammonia, and 
ength of time most favorable for the solution of the glucina. 
One gramme of pure glucina was treated with carbonate of 
ammonia, under the same circumstances of temperature and con- 
centration, for three, seven, eleven, and sixteen days. After ten 
days, with carbonate of ammonia of 1-080 specific gravity and 
15° C., the maximum amount was dissolved. the solution 
be kept longer than ten days, a precipitate of carbonate of glu- 
cina will begin to form, and at the expiration of sixteen days, 
fifteen per cent less of the original amount will go into solution. 
It was found advisable to separate the glucina after the expira- 
tion of a week. I observed that it was preferable to precipitate 
the two earths in the first instance with carbonate of ammonia, 
as the glucina was then more soluble than if first thrown dow: 
by ammonia and afterwards digested in the carbonate. © 
of potassa and carbonate of soda dissolve the precipitate of 
3. By caustic potassa.—This method was first proposed by C. 
G.Gmelin.* The solution of alumina and glucina in chlorhydric 
acid is neutralized by a cold solution of eb 8 
By diluting the potassa with ten parts of water, and dissolving 
_ the glucina in chlorhydric acid, and re-precipitating by ammo- 
~ nia, I obtained very pure glucina, but always with loss of mate- 
* Pogg. Ann., xcii, 91. 
* Handwortb. 4. Chem, 2te Auf., ii, 1018. Pogg. Ann., xcii, 97. 
Am. Jour. Scr.—Szconp Senres, VoL. XXXVI, No. 106.—Juxy, 1863. 
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