COMPLETE A Process for the Manufacture of a Scent Essence termed Rhodinol.
Year: 1894

page_text: Date of Application, 8th Aug., 1894-Accepted, 22nd Sept., 1894
SPECIFICATION.
COMPLETE
A Process for the Manufacture of a Scent Essence termed Rhodinol.
I, PIERRE PROSPER MONNET, of 8 Quai de Retz, Lyons, in the Department
of the Rhône, France, Manufacturer do hereby declare the nature of this invention,
and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement :—
This invention relates to the manufacture of a scent essence, termed Rhodinol,
which has all the properties of, and is capable of replacing in its industrial purposes,
attar of roses, and consists of a process for the manufacture of the said essence of
rhodinol from a special source. I have found that the essences of commerce
obtained from the geranium and especially from the "pelargonium odoratissimum"
contain variable quantities of the said rhodinol.
By careful experiments I have succeeded in isolating the rhodinol from the
odorous or other components with which it is mixed, by operating in the following
manner;-
The raw essence of pelargonium is treated in a closed vessel, with an alcoholic
solution of potash or soda, in order to saponify the ethers to neutralize the free
acids, and to destroy the aldehydes with their disagreeable odour, that exist therein.
The operation is carried out as follows:-
The essence is placed in a digestor, and to it is added the alcoholic solution of
potash or soda, composed of the proportion of 250 grs. of alcohol with 150 grs. of
potash of 75% alkaline strength or of 250 grs. of alcohol with 110 grs. of soda
of 75% alkaline strength, to be mixed with one litre of essence of pelargonium : the
mixture is heated for two hours at 100° C., then the alcohol is separated by
distillation. The essence thus treated is washed once with water and then a second
time with a solution of sulphuric acid with a strength of 2 to a 100, so as to
eliminate the last traces of alkali. The essence is then washed twice with water, is
decanted, dried and submitted to a series of fractional distillations under vacuum.
The fractional distillations are divided preferably into three successive operations
in a suitable distilling apparatus under a pressure of 10 m/m of mercury above
vacuum.
1ST FRACTIONAL DISTILLATION.

page_text: In this distillation the distillate obtained in the prior distillation between
90° and 100° is put on one side, and each of the other four distillates are again
distilled within the same limits as in the preceding distillation.
In this last distillation the portions which distill between 100° and 115° diminish
considerably, and the major portion of the product passes over between
115° and 120°.
It is this last portion which contains the rhodinol. A good essence of
pelargonium should not contain less than 60% of this last distillate.
To complete the treatment, the distillate collected between 115° and 120° is
placed in an enamelled digestor, with crystallisable acetic acid in the proportions
of 1540 grs. of rhodinol and 1000 grs. of crystallisable acetic acid. The mixture
is heated for about 12 hours at 180° C. temperature and is then treated with water
to remove the acetic acid which has not reacted. The insoluble product, which is
acetic-ether of rhodinol, is washed several times, is dried, and distilled under
vacnum.
This ether distills regularly between 118° and 122°, under a pressure of 10 m/m
of mercury above vacuum.
It is saponified by suitable quantities of alcoholic potash or soda, which regenerates
the rhodinol. The regenerated rhodinol is washed first with distilled water, then
with acidulated water and then again with pure water, and afterwards dried and
submitted to a last rectification in vacuum. It then boils at 115° to 118°, under a
pressure of 10 m/m of mercury above vacuum, and presents an appearance of an
oily liquid quite colourless, possessing a delicious odour of roses.
The fractional distillates recovered between 90° and 100° C. from the second aud
third distillations should be collected and preserved. They are composed of a
mixture of a particular alcohol termed "Licaréol" and of a special acetone
identical to that which is contained in the essence of native menthene. This last
substance posseses a very penetrating odour of peppermint.
The acids separated by the potash and soda, and which were contained in the
form of ethers in the raw essence of pelargonium, are acetic acids, isobutyric,
isovalerianic, tiglic, or methylerotonic acids. The last, which is a rare product,
should be rigourously collected.
It is evident that in the before described process, the crystallisable acetic acid
may be replaced by acetic anhydride.
Having now particularly described and ascertained the nature of this said inven-
tion and in what manner the same is to be performed, I declare that what
I claim is ;-
The manufacture of essence of rhodinol (as a substitute for essence of roses)
from the natural essence of geraniums, particularly that of the "pelargonium
odoratissimum" by the following series of processes.
1st. The treatment of the essence of geraniumins or pelargoniums by alcoholic
potash or soda, with the object of saturating or neutralising the free acids, to
saponify the ethers, and to destroy the aldehydes of disagreeable odour, so that
these constituents may be eliminated by repeated washings.
2nd. The distillation of the essence, thus treated, by caustic soda or potash, in
several succesive fractional distillations, in order to separate the rhodinol as much
as possible from the other constituents of different boiling points; and to recover as
bye-products, a mixture of licaréol, and an acetone with an odour of menthene,
applicable for the preparation of scent essences.
3rd. The transformation of the raw rhodinol, thus obtained by fractional distillations,
into acetic-ether of rhodinol, by heating it under pressure with acetic acid, and

page_text: the purification of the acetic-ether of rhodinol thus formed, by repeated washings,
and distillations, and :-
4th. The saponification of the acetic-ether of rhodinol, thus obtained, by a
treatment with alcoholic potash or soda, and the completion of the purification of
the rhodinol thus regenerated, by washings and by one rectification.
All substantially as and for the purposes herein above set forth.
Dated this 8th day of August 1894.
FELL & WILDING,
Agents for the Applicant.