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XVI. On the Value in Absolute Alcohol of Spirits of different Specific Gravities. 
By George Fownes, Es(/., F.R.S., 
Professor of Practical Chemistry in University College , London. 
Received June 7, — Read June 17, 1847. 
Having been for some months past occupied with experiments on the fermenta- 
tion of sugar and molasses, and having found it necessary to construct for this pur- 
pose a new table of the quantity per centum by weight of absolute alcohol contained 
in spirits of different specific gravities, I venture to lay the same before the Royal 
Society, hoping that it may be found generally useful in inquiries of this kind, and 
also for other purposes. 
The Table was formed synthetically; absolute alcohol and distilled water were 
weighed out in the required proportions, mixed in small well-stopped bottles and 
well-shaken together. After standing three or four days the mixtures were brought 
to the temperature of 60° Fahr. exactly, and their specific gravities determined 
with great care. After the lapse of two or three days more this last-named operation 
was repeated, but in no case was it observed that any further contraction had oc- 
curred. Neither was the specific gravity of a mixture containing nearly equal parts 
alcohol and water which had been so examined changed by being inclosed in a 
strong accurately-stoppered bottle, and heated for some time to a temperature above 
its boiling-point. 
In this manner each alternate number in the Table (each even number) was ob- 
tained by direct experiment ; the others were then interpolated. When completed, 
the Table was examined by various methods calculated to test its accuracy, but no 
error of sufficient magnitude to limit its usefulness was detected. 
The absolute alcohol employed in these experiments was prepared in the following 
manner : — the strongest rectified spirit was agitated with half its weight of carbonate 
of potash deprived of water of crystallization, and left in contact with the salt some 
days. It was then decanted upon half its weight of powdered quicklime, made from 
black marble, contained in a metal still which could be perfectly closed. The mix- 
ture of spirit and lime was retained in a warm situation for a week or thereabouts, 
and then distilled by means of a water-bath. By this treatment the specific gravity 
of the alcohol was generally reduced to *796 or even below, and by a repetition of 
the process of digestion with powdered lime and re-distillation, the last traces of water 
were removed. In this manner, without difficulty, the very considerable quantity of 
absolute alcohol required for the experiments was procured. 
mdcccxlvii. 2 K 
