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XV. On the Specific Heat and other Physical Characters of Mixtures of Methylic 
Alcohol and Water , and on certain relations existing between the Specific Heat of 
a Mixture or Solution and the Heat evolved or absorbed in their formation. By 
A. Dupre, Ph.l)., Lecturer on Chemistry at Westminster Hospital. Communicated 
by William Odling, M.B. 
Received April 4, — Read May 16, 1872. 
The pure methylic alcohol was prepared according to the following process, devised by 
Mr. Chapman. Rectified wood-spirit is mixed with its own bulk of a saturated solution 
of calcium chloride, the mixture is heated to boiling and allowed to stand over night. 
The layer of oil found floating on the surface is carefully removed, and the fluid under- 
neath is mixed with about one volume per cent, of a saturated solution of lead acetate. 
An amount of sulphide of ammonium, not quite sufficient to precipitate all the lead, is 
next added, the precipitate, which carries down much colouring-matter and many minute 
globules of oil, is filtered off, or allowed to subside, and the clear fluid is distilled. To 
this distillate caustic soda in coarse powder is added, and after standing some time it is 
diluted with water and again distilled ; much resinous matter is thus removed, and the 
acetate of methyl is decomposed. The specific gravity of this second distillate is now 
brought to about *82 (if necessary, by treatment with potassium carbonate), after which 
it is mixed with one fourth of its bulk of a saturated solution of bisulphite of ammonium. 
The mixture is allowed to stand for several days, and is then filtered and distilled from 
a water-bath ; to the distillate a little sulphuric acid is added, and it is then redistilled, 
also from a water-bath. Finally a slight excess of caustic soda is added, and the liquid 
is once more distilled, when pure methylic alcohol passes over, which is rendered anhy- 
drous by several distillations over caustic lime. The purity of the spirit is tested by 
oxidizing 20 grammes of it with an excess of bichromate of potassium and sulphuric 
acid, when it should yield nothing but carbonic acid and water. 
The spirit thus prepared was perfectly miscible with water in every proportion ; it had 
at 10° C. a specific gravity of -81371, boiled at 5S°*6 C. at a pressure of 757-4 millims., 
and had a specific heat of 58-325 between the temperatures of 60° and 18°. 
Section I . — Specific Heat. 
The mixture *, the specific heat of which is to be estimated, is enclosed in a small 
annular brass vessel, which can be closed hermetically by means of a screw-plug. In 
the inner cylindrical space a fan-wheel is fixed, acting as a stirrer when the vessel is 
* For the method employed for the preparation of mixtures of the exact strength desired, see Section Y. 
MDCCCLXXH. 2 Z 
