November 5, 1870.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
375 
Tvas one of two that I had stuffed after keeping them 
alive for about a fortnight. It has suffered a little in 
.appearance from its captivity. 
The President expressed his interest in the singular 
facts laid before the meeting by their friend Mr. Stan¬ 
ford. The habits of birds included some phenomena 
which were startling by their uniformity and obedience 
to some hidden rule. Thus, the sea-birds frequenting 
the rocks near Tenby were in the habit of appearing for 
the season upon a certain and uniform day each year. 
Mr. Groves, remarking upon the powerful odour of 
guano evolved by the stuffed specimen upon the table, 
.said that the egg of the fulmar had also a strong smell. 
A Member referred to the recent Sea-birds Preserva¬ 
tion Act, mentioning that the island of St. Kilda was 
-specially exempted from its operation. 
Mr. Mackay stated that the deplorably destitute con¬ 
dition of the population of St. Kilda was ample justifica¬ 
tion for this exemption. Sea-birds and their eggs might 
be said to be the sole food of the people, who were often 
■on the verge of starvation. Food was occasionally sent 
to the island, but sometimes the sea was so rough that 
no communication could take place for a period of months. 
He had understood that the skin of the bird was made 
into shoes. 
A Few Notes on Aloes. 
BY WILLIAM A. TILDEN, B.SC. LOND., F.C.S., 
Demonstrator of Practical Chemistry to the Pharmaceutical 
Society. 
In the list of subjects for investigation issued to the 
members of the Conference is the following question, No. 
176 :—“ Compound Decoction of Aloes loses bitterness 
after some time ; to what is this due ?” 
Before attempting to answer this question, a few points 
in the chemistry of aloes require notice. 
In the last edition of Pereira’s ‘ Materia Medica’ four 
proximate principles are enumerated as forming the most 
important constituents of aloes. 
1. Aloetin, aloesin, amorphous aloin, bitter principle 
of aloes. 
2. Crystallized or hydrated aloin. 
2 . Resin. 
4. Aloesic acid; supposed by some to be gallic acid. 
Experiments made by myself, in addition to those al¬ 
ready published by Mr. Groves and other chemists, in¬ 
duce me to adopt an opinion respecting the constitution 
of aloes somewhat modified from the foregoing. 
I. Aloetin. —The first of these bodies certainly forms a 
constituent very important as to quantity of all the 
varieties of aloes. There can be no doubt that it is the 
product of the alteration of crystallizable aloin, partly 
by the action of heat, partly by the oxidizing action of 
the air. I regard it as a mixture of anhydrous aloin, 
which is capable in the presence of water of recovering 
its crystalline condition, and the brown oxidized sub¬ 
stance referred to further on. 
II. Crystallizable aloin is the body to which especially 
■all the varieties of aloes owe their bitterness. Its isola¬ 
tion is usually thought to be a matter of some difficulty, 
but the following simple process will furnish any desired 
quantity,—pounds if necessary. 
Select a specimen of Barbadoes aloes, the most power¬ 
fully odorous that can be procured, bright-looking, and 
not the most waxy: break it up and dissolve it in a 
quantity of boiling distilled water, to which a few drops 
of sulphuric, sulphurous, or hydrochloric acid have been 
added. The proportions employed may be those of the 
Pharmacopoeia for Extractum Aloes, viz. one pound to a 
gallon. Let the liquid stand a night to deposit resin, 
then pour it off and evaporate quickly till, if 1 lb. of 
aloes have been used, about 2 lbs. of liquid remain. 
This left for twenty-four hours will deposit an abun¬ 
dant crop of yellow crystalline matter. The fluid portion 
poured off and duly concentrated yields a first-rate ex¬ 
tract. The yellow crystals must be well drained and 
pressed, and will yield pure aloin by recrystallization 
once or twice from water mixed with a small proportion 
of rectified spirit. If the selection of the aloes be looked 
to, the product will amount to about 20 per cent, of the 
material employed. 
Aloin has been said to be with great facility decom¬ 
posed or altered by the simple application of heat to its 
aqueous or alcoholic solution. I have found, however, 
that it will bear without appreciable change compara¬ 
tively rough treatment in this way, provided the solution 
is quite neutral or slightly acidified. A little pure aloin 
dissolved in distilled water may be evaporated to dryness 
and heated till it fuses, and then redissolved in water, 
and this operation repeated several times, but the aloin 
undergoes but slight change of colour, and will still crys¬ 
tallize on letting the solution stand for an hour or two, or 
almost immediately on stirring. The transparent yellow 
varnish left by evaporating solutions of it consists merely 
of anhydrous aloin; treatment with water restores to it 
its crystalline state. It is of course already known that 
if kept in a moist state on a water-bath for some time, 
the pure substance becomes gradually brown, and assumes 
the appearance of Socotrine aloes; but this is a compara¬ 
tively slow process, and even after some time a consider¬ 
able quantity of the aloin is still capable of crystallizing. 
A further illustration of its stability is exhibited in the 
following experiment and accompanying specimen. 
About ten years ago, a paper by Ivosmann appeared in the 
Journal de Pharmacies the object of which was to show 
that aloes was a mixture of glucosidic bodies. The ex¬ 
periments by which grape sugar was obtained, and its 
presence indicated by the asserted production of alcohol 
and carbonic acid, were performed by Kosmann solely 
upon Cape aloes. I have made a number of experiments 
which convince me that he is quite incorrect in his state¬ 
ments, but as I hope to reproduce the subject at a future 
meeting, I will cite only one experiment made with pure 
aloin. Some aloin was dissolved in about an equal weight 
of oil of vitriol (it forms a clear orange syrup) ; the solu¬ 
tion was gently heated for a few minutes, and then poured 
into water and kept boiling for about four hours. 
Saturated by excess of pure carbonate of barium, fil¬ 
tered and evaporated on a water-bath, a minute quantity 
of barium retained in solution precipitated by dilute sul¬ 
phuric acid and the liquid further concentrated, unaltered 
aloin was deposited in yellow crystals. A part of the 
solution which had been thus treated was submitted to 
the fermentation test. Three tubes full of mercury were 
inverted in a small mercurial trough. Into the first was 
introduced some washed yeast and distilled water. _ Into 
the second some washed yeast and a weak solution _ of 
sugar. Into the third some yeast and the boiled solution 
of aloin. The first and third gave no bubbles of gas 
larger than a pin’s head; the second tube was completely 
filled with C0 2 in half an hour. 
To ascertain if the aloin prevented fermentation, two 
similar tubes were set up. The first contained yeast, 
distilled water and sugar; the second had in addition a 
portion of the solution which had been boiled and tested 
as above. Both gave gas in about half an hour nearly 
equally. A portion of the same sample of yeast was 
used in all these cases. There is consequently no sugar 
produced by boiling aloin with acids, and the aloin un¬ 
dergoes practically no change. 
The copper test is inapplicable, inasmuch as pure aloin 
which has undergone no manipulation reduces alkaline 
copper solutions rapidly and freely.* 
Aloin gives no apparent change with tartar emetic nor 
with ferrous salts, but with ferric salts it strikes an olive 
coloration, which is destroyed by reducing agents. 
III. The substance termed resin t which abounds in all 
kinds of aloes, is not very happily so called, for it is 
soluble in considerable quantity in hot water. It is said 
* I have found that many other bodies besides the glucoses 
do this; amongst others, tannin and orcin. 
