CapucAs Mewe} The Aluminium-Iodine Reaction.
does not take place when ready formed iodide of aluminium 1 first organic compounds which contain both oxygen and
is employed. . . 2 metal and are capable of distillation. They are soluble
The several changes thus described are typical of our more or less in ether, alcohol, and benzol, but are decomaluminium-jodine
 reaction.” The reaction is quite dis- posed by water with the formation of aluminium hydrate
{in& from that which has lately given beautiful results in and the alcohols. They were found to have the following
the hands of Friedel; and we have investigated its ap- specific gravities at 4° C, :(—
nlicability both for the production of new compounds, and
for distinguishing between different classes of organic
sodies, as well as for throwing light on their comparative
constitution.
Neither zinc nor iron, nor, as far as we know, any other
metal can be substituted for aluminium in this rea&ion;
but the chloride or bromide may be used instead of the
iodide, though with less advantage.
Recent Results.
For decomposing an alcohol a small quantity of iodine
is dissolved in it, the necessary excess of aluminium is
added, and the mixture is heated. Evolution of hydrogen
gas begins immediately, and proceeds somewhat rapidly
until the whole of the metal has passed into combination.
In this way the aluminium derivaties of the following aicohols
 have been prepared :—Ethylic, normal propylic,
iso-butylic, amylic, benzylic, phenylic, cresylic, and thymolic.
 The first four of these aluminium derivatives may
be distilled i» vacuo, and they have thus been separated
irom the other solid produéts of the reacion, and obtained
in a pure condition. The other aluminic alcohols cannot
be distilled, at any rate not without very considerable
decomposition. The following alcohols, however, behave
in a different way with the reagent :—
Methyl alcohol is not decomposed by aluminic iodide
and aluminium, but in presence of free iodine it parts
slowly with hydrogen, and the same happens when an
aluminium-platinum couple is substituted for the metallic
aluminium.
Iso-propyl alcohol.—This is not acted upon in the least
by the reagents.
Cetyl alcohol.—On heating this compound with the
reagent, hydrogen is slowly set free, untiil the temperature
 reaches about 200° C., when another chemical change
is set up, resulting in the formation of cetyl iodide and
aluminic hydrate.
Allylic alcohol.—The first action is identical in chara@er
with that which takes place with the alcohols of the
Cn Hzui1 OH series. Instead, however, of the whole of
the liberated hydrogen escaping, about 30 per cent of it
aéts upon the excess of alcohol, splitting it up into propylen
 and water.
Ethene alcohol.—The reagent does not liberate hydrogen
from this substance, and has but a very slight action upon
ite
Propenyl alcohol.—No hydrogen is evolved, but a double
lecomposition ensues at about 140° C., yielding allyl
iodide, free iodine, and aluminium hydrate; if aluminium
be in excess, aluminic hydrate and allyliciodide are the sole
products,
Aldehyd. — Hydrogen is not set free from this compound.

The general result, then, of these observations is that
the reagent substitutes aluminium for the basic hydrogen
of water, and of all the alcohols hitherto tried, whether of
the methyl, allyl, benzyl, or phenyl series, with remarkable
 exception of iso-propyl alcohol, On the other
hand, it does not substitute aluminium for hydrogen in the
dihydric or tribydric alcohols, nor yet with aldehyd. The
reation with the ethers and glycerin is of a different
charaéier, as, in addition to an aluminium compound, the
iodides of the positive radicals are formed.
General Properties of the Aluminium Alcohols.
The aluminium alcohols are solid at the ordinary temperature,
 and fuse generally into clear liquids. They
possess, in a marked degree, the property of remaining
fluid far below their melting-points, Those of the methyl
series distil unchanged at reduced pressures, affording the

Action of Heat.—All these alcohols are decomposed at
1 temperature somewhere about their boiling-points, and
t became an interesting subje& of inquiry whether they
were resolved into alumina, and the alcohol and its olefine,
or into alumina and the ether. Both these a&ions seem
to take place. Thus aluminic ethylate appears to be decomposed
 by heat in both ways, but mainly according to
he following scheme :—
(C2H;0)6Al,=Al,03=3C,H;+3C, HO.
Aluminic phenylate, on the other hand, is capable of decomposition
 mainly in the following way :—
(CeH350)6Al2= Al;0+3(C6Hs),0.
It must not, however, be supposed that these decompositions
 take place without other reactions. Some of the
bodies thus produced are new ones, and we are at present
engaged in their investigation.
The most interesting decomposition is that of the thymolate.
 When heated it splits up into alumina, propylene,
and bodies of the cresylic group. One of these is a solid
body, which, when re-sublimed or crystallised from alcohol,
 presents itself in most beautiful pearly plates. Its
properties resemble rather those of an ether, and concordant
 analyses of different specimens and determinations
of vapour density give the anomalous molecular formula
C14H130, but its real constitution is still the subje& of
‘nquiry,
Theory of Reaction.
The rea&ion by which the compounds described above
are formed is by no means clear at first sight. It is difficult
 to imagine that the presence of a haloid salt should
letermine the direct replacement of hydrogen by alumirium
 in water or in alcohol. We believe, however, that
the presence of hydriodic acid in the reaction with the
aromatic alcohols furnishes the true key to the chemical
change. The first action is in all probability that of a
seciprocal decomposition between two binary compounds,
:he alcohol and aluminium jodide,—forming a certain proportion
 of aluminium alcohol and hydriodic acid. But the
metallic aluminium present at the same time decomposes
‘he hydracid with evolution of hydrogen and the produ&ion
of more aluminium iodide, which brings about a further relistribution
 of the elements and the formation of more of
:he aluminium alcohol and the hydriodic acid, and so on
iill the chemical change is complete, The following equations
 express these changes, which take place alternately,
ar rather continuously :—
(1) 6(Cx Hin -50.H)ALIs= Al(Cn Hz 4 -»0)6+6HI.
f2.) 6HI+Al,=AlIs+6H.
[t is evident that, as the iodine does not enter into the
final products, a very small quantity of it is sufficient to
carry on the continuous chemical change.
There can be little doubt that the same rea&ions occur
in the case of the alcohols of the C, Hyp +10.H series,
but the amount of hydriodic acid formed in the reciprocal
lecomposition is perhaps very small, and the tenacity
with which it is held by the alcohol has made it impossible
or us to prove its separate existence. The same remark
applies also to water, which we believe to a& in the same
vav. Indeed we know. from the experiments of Roscoe;