BROM-ALOINE.—When an excess of bromine is poured into a cold aqueous solution of aloine, a bright yellow precipitate is immediately produced, the amount of which increases on standing, while at the same time the supernatant liquid becomes very acid from containing free hydrobromic acid. The precipitate, after it has been washed with cold water to remove adhering acid, is dissolved in hot spirits of wine; and on the cooling of the solution it is deposited in bright yellow needles radiating from centres, which attach themselves to the bottom and sides of the containing vessel.
The crystals of brom-aloine are considerably broader than those of aloine, and have a richer yellow color and a higher lustre. Brom-aloine is quite neutral to test-paper, is not so soluble in either cold water or cold spirits of wine as aloine, but dissolves very readily in hot spirits of wine.
I. 0.421 grm. substance dried in vacuo gave 0.547 carbonic acid and 0.103 water.
0.856 grm. gave 0.848 bromide of silver = 42.16 Br.
II. 0.300 grm. substance gave 0.391 carbonic acid and 0.078 water.
0.661 grm. substance gave 0.649 bromide of silver = 0.2762 Br. = 41.78 per cent.
| Calculated numbers. | I. | II. | ||
|---|---|---|---|---|
| 34 C | 2550.00 | 35.73 | 35.43 | 35.53 |
| 15 H | 187.50 | 2.62 | 2.71 | 2.86 |
| 14 O | 1400.00 | 19.63 | 19.70 | 19.83 |
| 3 Br | 2998.89 | 42.02 | 42.16 | 41.78 |
| 7136.39 | 100.00 | 100.00 | 100.00 | |
The brom-aloine employed in these analyses was prepared at two different times. It is plain therefore from these results, {182} that this bromine compound is aloine, C34 H18 O14 in which 3 equivs. of hydrogen are replaced by 3 equivs. of bromine.—The formula of brom-aloine therefore is C34 H15 O14 Br3.
When a stream of chlorine gas was sent for a considerable time through a cold aqueous solution of aloine, a deep yellow precipitate was produced. It contained a great deal of combined chlorine; but as it could not be made to crystallize, it was not subjected to analysis. In the present instance, and in those of several other feeble organic principles, such as orcine, chlorine appears to act some what too strongly, so that the constitution of the substance is destroyed, and merely uncrystallizable resins are produced. Bromine, on the other hand, is much more gentle in its operations, and usually simply replaces a moderate amount of the hydrogen in the substance, so that, as in the case of orcine and aloine, crystalline compounds are produced.
It has long been known to medical practitioners, that the aqueous extract of aloes is by far the most active preparation of that drug. The reason of this is now very plain, as the concentrated extract of aloes obtained by exhausting aloes with cold water consists chiefly of aloine, by much the larger portion of the resin being left undissolved. Mr. Smith informs me, that from a series of pretty extensive trials, from 2 to 4 grs. of aloine have been found more effective than from 10 to 15 grs. of ordinary aloes. Aloine is, I should think, therefore, likely ere long, to supersede, at least to a considerable extent, the administration of crude aloes.