The Aluminium-lodine Reaction. i
——— Te Tr —
ippeared to have an effe® upon the junctions, as after one
or two series of compression experiments they could be no
longer relied upon, and worked very irregularly, The only
vay to obviate this difficulty was, therefore, to prevent the
junctions being submitted to pressure at all, and this was
:ffected by soldering a stout iron tube, about } inch in--ernal
 diameter, into the brass flange, which reached to
bout the centre of the bottle. The tube was closed at
the bottom and contained a few c.c. of alcohol, into which
the junéion was lowered from the outside. The part of
the tube which went into the bottle was then frozen into
‘he test-tube with water, and thus sustained all the pressure
 while the alteration of temperature was conveyed
shrough the iron to the junction.
This worked exceedingly well, giving exaély the same
results as before, the only drawback being that the action
was very sluggish, the galvanometer taking about two
minutes to come to rest after each addition of pressure.
The above results seem to prove that the calculated value
of the variation of the freezing-point of water, deduced
rom the observed difference of volume of ice and water,
and the latent heat of fluidity at the melting-point under
one atmosphere of pressure, is identical with the mean exserimental
 value obtained from a series of observations
sxtending to 700 atmospheres. From Clapeyron’s formula
we are thus entitled to infer that TV =constant, where T
:s absolute temperature, V is difference of volume, and L
s latent heat of fluidity. If V is assumed to be approxinately
 constant, then T and L thus is the latent heat of
ice, diminished as the freezing-point is lowered by pres
sure. ‘This is in accordance with the deductions of
Slausius* from other considerations.

“
eee ———
packed afterwards in ice. "It will be seen, from the following
 set of readings, that the deflection was about the
same as when the jun&ion was frozed into a block of ice,
the only difference being that whereas the galvanometer
in the first series assumed its new position immediately
the pressure was applied, the instrument now required
from two to three minutes before coming finally to rest, the
a@ion being far more sluggish.
Zero= +06.
Position on Scale. Difference.

JreSsure.

25
50 -
75 — 53
{00 - 74 }
125 —- 91
50 —- 110
75 -130
200 149
Mean defleGion for 25 atmospheres is 19°4 divisions of the
scale.

7

Series IV.
Brine was placed round the junéion in the bottle, the
latter being afterwards packed in ice and salt, to reduce
the temperature of the brine to—-20° C., the other junétion
being placed in ice and salt on the outside. The junctions
were then connected up with the galvanometer, and
allowed to remain untill the temperatures became
equalised :—
Zero+8s.
Atmospheres, Position on Scale. Increase.
25 + 98
50 +106
75 +115
[G1] +121
i25 +128
150 +134
175 +138
200 +142
in this case a heating effet was produced, which
seemed, however, to decrease as the pressure was increased.
It represents an increase of gy of a degree C. for the whole
200 atmospheres.

HE ALUMINIUM-IODINE REACTION.t
By]. H. GLADSTONE, Ph.D, F.R.S.,and
ALFRED TRIBE, F.CS,,
Lecturer lon Chemistry in Dulwich College.

ABouT four years ago we pointed out a reaction of iodide
»f aluminium which, as far as we are aware, has no precise
analogue in the science of chemistry, and which has led
‘0 the discovery of several volatile aluminjum alcohols.
it is well known that neither water, alcohol, nor ether is
jecomposed by metallic aluminium, and that each of these
sodies will dissolve iodine without entering further into
:ombination with it; but we found that by the joint action
>of these two elements, it was possible to split up the
above-mentioned liquids, = Water, though forming a
iefinite hydrate with the iodide of aluminium, is decomsosed
 by it in the presence of an excess of the metal,
aydrogen being evolved and aluminic hydrate formed.
[his takes place at the ordinary temperature.
Alcohol in a similar manner is decomposed by the joint
1&ion of metallic aluminium and its iodide, with the ultinate
 production of hydrogen gas, aluminic ethylate, and
varying amounts of aluminic iodoethylate proportional to
‘he quantity of aluminic iodide employed. A small quanity
 of the iodide suffices to bring about the formation of
1 very large amount of the ethylate; in fact, the process
would he a continuous one, were it not that the solid proiu@s
 gradually put a stop to the reaction.
Ether is not affe@ed by aluminic iodide and aluminium,
»ut when exposed to iodine and aluminium simultaneously
t suffers a violent decomposition, iodide of ethyl and the
iluminic iodoethylate being the ultimate produds,
Amylic ether behaves in a similar manner, and the
\cetates of ethyl and amyl give analogous results; but the
-eaction is not an ordinary double decomposition, for it
% Phil. Mag., 1851.
+ A Paper read before the Royal Society, Ju ne 17, 1880.

Series V.
The junction in the flange was frozen into a solid block
of ice, and placed in a bottle, surrounded with brine at
— 20° C., the bottle being packed in ice and salt. A very
slight heating effe@ was produced, which only amounted
to about x4 divisions for 200 atmospheres.
Series VI.
These experiments were made with the junction frozen
into a test-tube with water, and placed in the bottle with
mercury surrounding it instead of water. This gave
2xacly the same deflection of the galvanometer as when
water was employed, only the experiment could not be
sarried on for a long time, as the ice melted with considerable
 rapidity, from the heating of the mercury by
compression.
Series VII, :
As in several cases the junction that was placed inside
the bottle, and which had been several times subjeled to
high pressures, appeared to be affected by the compression
and worked somewhat irregularly, it was thought advisable
to subjeét both the jun&ions to the same compression, sO
as to have them both under the same conditions. For
this purpose both junctions were passed through the brass
ange, being well insulated by marine glue, the one remaining
 on the outside of the test-tube in which the other
was frozen.
The results with ice were exactly the same as when one
un&ion was placed outside the bottle, but pressure still