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Page 87
The rule might have been calculated so as to show _at once_ the
equivalent, without dividing by 4; but it would have required several
more places of decimals; it will give the required quantity to a
fraction of a fluid drachm.
* * * * *
PURIFICATION OF SPIRITS BY FILTRATION.
BY MR. W. SCHAEFFER.
Instead of resorting to repeated distillations for effecting the
purification of spirits, Mr. Schaeffer proposes the use of a filter. In
a suitable vessel, the form of which is not material, a filtering bed is
constructed in the following manner:--On a false perforated bottom,
covered with woollen or other fabric, a layer of about six inches of
well-washed and very clean river sand is placed; next about twelve
inches of granular charcoal, preferring that made from birch; on the
charcoal is placed a layer of about one inch of wheat, boiled to such an
extent as to cause it to swell as large as possible, and so that it will
readily crush between the fingers. Above this is laid about ten inches
of charcoal, then about one inch of broken oyster shells, and then about
two inches more of charcoal, over which is placed a layer of woollen or
other fabric, and over it a perforated partition, on to which the spirit
to be filtered is poured; the filter is kept covered, and in order that
the spirit may flow freely into the compartment of the filter below the
filtering materials, a tube connects such lower compartment with the
upper compartment of the filter, so that the air may pass freely
between the lower and upper compartments of the filter. On each, of the
several strata above described, it is desirable to place a layer of
filtering paper.
The charcoal suitable for the above purpose is not such as is obtained
in the ordinary mode of preparation. It is placed in a retort or oven,
and heated to a red heat until the blue flame has passed off, and the
flame become red. The charcoal is then cooled in water, in which
carbonate of potash has previously been dissolved, in the proportion of
two ounces of carbonate to fifty gallons of water. The charcoal being
deprived of the water is then reduced to a granular state, in which
condition it is ready for use.
* * * * *
ON ESSENTIAL OIL OR OTTO OF LEMONS.
BY JOHN S. COBB.
(_Read before the Chemical Discussion Society._)
I have recently made some experiments with oil of lemons, of which the
following is a short account:--
Being constantly annoyed by the deposit and alteration in my essence of
lemons, I have tried various methods of remedying the inconvenience.
I first tried redistilling it, but besides the loss consequent on
distilling small quantities, the flavor is thereby impaired. As the oil
became brighter when heated, I anticipated that all its precipitable
matter would be thrown down at a low temperature, and I applied a
freezing mixture, keeping the oil at zero for some hours. No such
change, however, took place.
The plan which I ultimately decided upon as the best which I had
arrived at, was to shake up the oil with a little boiling water, and to
leave the water in the bottle; a mucilaginous preparation forms on the
top of the water, and acquires a certain tenacity, so that the oil may
be poured off to nearly the last, without disturbing the deposit.
Perhaps cold water would answer equally well, were it carefully agitated
with the oil and allowed some time to settle. A consideration of its
origin and constitution, indeed, strengthens this opinion; for although
lemon otto is obtained both by distillation and expression, that which
is usually found in commerce is prepared by removing the "flavedo" of
lemons with a rasp, and afterwards expressing it in a hair sack,
allowing the filtrate to stand, that it may deposit some of its
impurities, decanting and filtering. Thus obtained it still contains a
certain amount of mucilaginous matter, which undergoes spontaneous
decomposition, and thus (acting, in short, as a ferment) accelerates a
similar change in the oil itself. If this view of its decomposition be a
correct one, we evidently, in removing this matter by means of the
water, get rid of a great source of alteration, and attain the same
result as we should by distillation, without its waste or deterioration
in flavor.
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