n 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.

I am, however, aware that some consider the deposit to be modified
resin.[H] Some curious experiments of Sa