44 
ALOINE. 
shape, which unassisted sight enabled me to recognise as crystals of aloine — 
the microscope afforded more certain evidence. 
I will here observe parenthetically, that by cautiously blowing a bubble 
of a suspected extract, a very trifling amount of crystallization may be 
detected, that cannot readily be discovered in any other way. 
The extract that afforded this indication had been prepared by exhausting 
Socotrine aloes with boiling water ; filtering the cooled liquor, a little car- 
bonate of magnesia being previously added; and evaporating by a steam 
heat. The exhaustion requires a little knack. The aloes should be coarsely 
powdered, and sifted through a 40-hole brass sieve, then shaken lightly off a 
wide spatula into the boiling water, kept in constant agitation during the 
addition, and maintained in that state for twenty minutes after. The aloes 
will by this means be completely exhausted, and, by allowing the liquor to 
stand quiet till cold, the resinoid substances will deposit and adhere to the 
bottom and sides. The magnesia is added without decanting the liquor 
from the vessel. It filters very readily through serge, affording a perfectly 
bright liquid and extract. It is rendered turbid by the addition of acid. 
Aloine has not been permanently introduced into medical practice in this 
part of the world, so that I had no inducement to prepare a larger quantity 
than sufficed for experiment. Indeed, in investigations in general, the 
smaller in reason the quantity of material operated on, the greater will be 
the care expended on if, and less dubious the results arrived at — the chief 
disadvantage being the loss occasioned by not being able to economise the 
mother-liquors. 
One ounce of Socotrine aloes was therefore powdered and exhausted as 
previously described. When cold, hydrochloric acid was added to slight 
acidulation — a resinous precipitate was formed, which caused filtration to 
proceed with great difficulty. The addition of finely-powdered wood char- 
coal would have much facilitated it. Washed arrowroot has not so good an 
effect. The solution was, after filtration, evaporated by a water-bath to the 
consistence of syrup, transferred to a small basin covered by bibulous paper, 
and set aside on a shelf of the laboratory. 
In less than a week crystallization had commenced ; in a fortnight it had 
become a mass of crystals, that had grown irregularly, considerably above 
the level of the liquid. They were transferred to coarse blotting-paper, 
allowed to drain a day or two, then shifted to another piece, wrapped in it, 
and gently pressed by means of a weight. Cautiously proceeding thus, they 
were at last powerfully pressed with a screw, and presented the appearance 
of a brown-coloured brittle mass. This was dissolved in as small a quan- 
tity as possible of boiling water, allowed a few days to crystallize, and then 
treated as before. A third crystallization sufficed to procure crystals of a 
pale lemon colour (pure aloine), which weighed when dry 48 grains — 10 per 
cent, of the aloes employed. I found it was necessary to dry them in the 
compressed mass, closely wrapped in blotting-paper, and at a temperature of 
about 100. The surface and edges only were oxidized, and were removed 
before powdering and weighing. When thoroughly dry, it does not appear 
to undergo change at the ordinary temperature. When damp, however, and 
at the same time exposed to heat, it oxidized rapidly, and could be made to 
assume almost exactly the appearance of the aloes whence it was originally 
taken. 
I am therefore of opinion that it is not to their possessing a vitreous cha- 
racter, but to circumstances connected with the composition of the original 
juice from which they are made, that the various degrees of facility with 
whicli aloine may be obtained from them is due, and that aloine may be pro- 
cured from all that have not been actually carbonized. 
With respect to its purgative power, of which M. Robiquet denies it the 
