IMPROVEMENTS IN THE REFINING OF SUGAR
Year: 1878

page_text: LETTERS PATENT to Hunter Henry Murdoch, of the Firm of Murdoch and
Whiteman, of No. 7, Staple Inn, in the County of Middlesex, Patent Agents,
for the Invention of "IMPROVEMENTS IN THE REFINING OF SUGAR." A com-
munication from abroad by Emilo Barrault, of Paris, France, Civil Engineer.
aled the 3rd September 1878, and dated the 1st June 1878.
PROVISIONAL SPECIFICATION left by the said Hunter Henry Murdoch at
the Office of the Commissioners of Patents on the 1st June 1878.
HUNTER HENRY MURDOCH, of the Firm of Murdoch and Whiteman, of No. 7,
"IMPROVEMENTS IN THE
Staple Inn, in the County of Middlesex, Patent Agents.
REFINING OF SUGAR." A communication from abroad by Emile Barrault, of Paris,
France, Civil Engineer.
This Invention consists of an improved process of refining sugar, and relates
especially to sugar which has been manufactured in accordance with one or more of
the processes described in the Specification of Letters Patent granted to me, and
bearing date the 20th January A.D. 1876, No. 240, and in a Provisional Specifi-
cation filed by me, and bearing date the 10th December, A.D. 1877, No. 4682.
The object of the present Invention is to obtain white sugar of a high degree of
purity from cane juice or from sugar of low quality, without the use of animal
charcoal, and thereby to avoid the loss of sugar which is incurred by the use of
animal charcoal, and to reduce the cost of the process of refining.
When cane juice or raw sugar is treated according to the processes described in
either one or other or both of the aforesaid Specifications, so far as relates to the
processes of liming, gassing, boiling, filtering, re-gassing and re-filtering (but without
filtering the cane juice or other solution of sugar through animal charcoal), the
sugar so obtained contains a certain amount of lime and adhering impurities which
These faults
give it a dull or grey colour, and an objectionable smell and taste.
have hitherto rendered the use of animal charcoal essential in carrying out the said
processes when it has been desired to make white sugar.

page_text: According to the present Invention, the cane juice or solution of raw sugar
which has been treated according to one of the processes of treatment with lime
and carbonic acid described in either one or both of the before-mentioned Specifica-
tions, and has thereby been clarified, is instead of being passed through animal
charcoal concentrated at once either in a vacuum pan or in any other suitable form
of evaporator until it crystallizes, and the first jet or crop of crystals so obtained, is
separated from the adhering syrup or molasses.
The crystals thus manufactured form a raw material which is treated as herein-
after described for the manufacture of white sugar.
When the process described in the Specification of the aforesaid Patent, No. 4682,
A.D. 1877, is used, all the jets of sugar being of similar purity, will form suitable
raw material for the present process.
The use of charcoal in refining the sugar made as aforesaid, is dispensed with by
using in lieu of the filtration by means thereof the following process, viz. re-dissol-
ving the said sugar in water of a good degree of purity, and boiling down the
solution so obtained and crystallizing it. The masse cuite obtained by this boiling
down of the re-dissolved sugar is cooled and separated from the adhering syrup
which carries away the impurities. The crystals left will be almost pure white
sugar.
If the solution of the sugar in water is turbid, it may be filtered before being
crystallized.
The syrup from these crystals may be put back into the first jet syrup obtained
from the sugar which has not been re-dissolved.

page_text: +
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Hunter Henry Murdoch in the Great Seal Patent Office on the
30th November 1878.
HUNTER HENRY MURDOCH, of the Firm of Murdoch and Whiteman, of No. 7,
Staple Inn, in the County of Middlesex, Patent Agents. IMPROVEMENTS IN THE
REFINING OF SUGAR." A communication from abroad by Emile Barrault, of Paris,
France, Civil Engineer.
This Invention consists of an improved process of refining sugar, and relates
especially to sugar which has been manufactured in accordance with one or more of
the processes described in the Specifications of Letters Patent granted to me, and
bearing date the 20th January, A.D. 1876, No. 240, and the 10th December, A.D.
1877, No. 4682 respectively.
The object of the present Invention is to obtain white sugar of a high degree of
purity from cane juice or from sugar of low quality without the use of animal
charcoal, and thereby to avoid the loss of sugar which is incurred by the use of
animal charcoal, and to reduce the cost of the process of refining.
When cane juice or raw sugar is treated according to the processes described in
either one or other or both of the aforesaid Specifications, so far as relates to the
processes of liming, gassing, boiling, filtering, re-gussing, and re-filtering (but
without filtering the cane juice or other solution of sugar through animal charcoal),
the sugar so obtained contains a certain amount of lime (partly in combination
with glucose and other analagous substances) and other adhering impurities which
give it a dull or gray colour and an objectionable smell or taste. These faults have
hitherto rendered the use of animal charcoal essential in carrying out the processes
described in the aforesaid Specifications, when it has been desired to make white
sugar.
According to the present Invention, the cane juice or solution of raw sugar which
has been treated according to one of the processes of treatment with lime and
carbonic acid described in either one or both of the aforesaid Specifications, and has
thereby been clarified, is instead of being passed through animal charcoal concen-
trated at once, either in a vacuum pan or in any other suitable form of evaporator,
until it crystallizes, and the first jet or crop of crystals so obtained is separated
from the adhering syrup or molasses.
The crystals thus manufactured form a raw material which is treated as herein-
after described, for the manufacture of white sugar therefrom.
When the processes described in the Specification of the aforesaid Patent, No.
4682, A. D. 1877, are used, all the jets of sugar being of similar purity, will form
suitable raw material for the present process.
The use of animal charcoal in refining the sugar made as aforesaid is dispensed
with by using in lieu of the filtration by means thereof the following process, viz.
re-dissolving the said sugar in water of a good degree of purity, and boiling down
the solution so obtained and crystallizing it. The masse cuite obtained by this
boiling down of the re-dissolved sugar is cooled and separated from the adhering
syrup which carries away the impurities. The crystals left will be almost pure
white sugar.
If the solution of the sugar in water is turbid, it may be filtered before being
crystallized.
The syrup from the crystals may be put back into the first jet syrup obtained
from the sugar which has not been re-dissolved.
Having now described the nature of the said Invention, I will proceed to describe
the manner in which the same is to be performed.
I would premise that this process is only applicable to the refining of certain
kinds of sugar, and is most specially applicable to those sugars which have been
manufactured partly in accordance with the instructions in the Specifications of the

page_text: aforesaid Letters Patent granted to me, and bearing date respectively the 20th
January A.D. 1876, No. 240, and the 10th December, A.D. 1877, No. 4682, but
without having filtered the syrups or solutions through animal charcoal.
I may explain more clearly the character of the sugars to which this process of
refining is applicable, by saying that the process depends upon the differences
between the relative degrees of solubility of the sugars to be refined and of the
impurities present in those sugars, and also upon the affinity which those impurities
have for the crystallizable sugar. Thus, for instance, in many samples of ordinary
sugar used for refining purposes, the glucose which is present as one of the impu-
rities, is in such a high proportion relatively to the crystallizable sugar, and has
such an affinity for the crystallizable sugar, that it adheres to the crystals during
the cooling process, and cannot be subsequently removed by washing in the centri-
fugal machines without dissolving a large amount of the crystallized sugar, while
the latter even after centrifugalling is of inferior quality.
The colouring matters in these sugars are so much less soluble than the sugar
itself, that they become entangled in the crystals of sugar, and impart colour thereto,
unless the syrups have been filtered through animal charcoal. The process is not
therefore applicable to these kinds of sugars.
On the other hand, in the case of sugars which have been manufactured in
accordance with the aforesaid Specifications, even although the syrups or solutions
have not been filtered through animal charcoal, the glucose has been entirely
removed or converted into a very soluble glucate of lime, and the colouring matters
have been almost entirely removed or changed in their character, and rendered much
more soluble, so that the present process is applicable to these latter sugars.
The process succeeds on these sugars because the impurities contained in them
are relatively much more soluble in water than the crystallizable sugar present, and
consequently if the sugar is dissolved in water and re-crystallized, the crystals so
obtained will be more pure than the raw sugar from which they were obtained, and
the syrups will take away a relatively larger proportion of the impurities.
I am aware that to a limited extent this will be true of most samples of sugar,
but the special advantages of this process are only found when dealing with sugars
which are almost or quite free from free glucose or other low or uncrystallizable
sugars and from organic colouring matters, and which contain little or no lime
except as glucate of lime, and preferably not much of that. It is for this reason
that sugars manufactured in accordance with the Specifications of my aforesaid
Patents, but without the use of animal charcoal, are most suitable for treatment by
this process.
I will now proceed to describe the process which is used in lieu of filtering the
solution of sugar which is being refined through animal charcoal, or by which sugar
which has been manufactured as aforesaid, but has not been filtered through animal
charcoal, is refined according to this Invention.
.
A suitable sample of sugar having been selected as herein-before described, it is
dissolved in water. It is desirable to use water of a good degree of purity, and
especially water which is free from lime or alkaline salts. Distilled water is pre-
fernble when it is available, or if not available, it is preferred that the water should
have been boiled so as to free it from carbonic acid gas.
The sugar may be dissolved in the ordinary way by blowing up or in any other
convenient manner. The solution need not be diluted more than is necessary to
render it thoroughly fluid, and to make it filter freely through bag filters. If any
insoluble matter, either lime, carbonate of lime, or other substance is present, it is
preferred to filter the solution of sugar so as to separate these substances. This
filtration however is through ordinary bag filters, and not through animal charcoal,
that is to say, it is merely mechanical filtration and not chemical filtration, the
object of the filtration being simply to separate the insoluble impurities, and not as
in the case of filtration through animal charcoal to improve the colour of the
solution. The solution should in either case, whether filtered or not, be perfectly
free from suspended or insoluble matters. This solution of sugar whether filtered

page_text: or not, is then boiled down either in a vacuum pan or in any other suitable evaporator
and re-crystallized, since it is by the crystallization that the impurities are sepa-
rated. It is preferred to boil it down in the vacuum pan and crystallize it in the
pan, and afterwards pass the masse cuite into coolers and allow the crystallization
to proceed therein, as by this means the crystals of sugar become larger, and the
impurities are more perfectly separated. When the masse cuite has crystallized
sufficiently, it is passed into centrifugal machines, and the adhering syrups which
contain the impurities are thoroughly separated. The crystals are washed in the
machines sufficiently to separate and remove the adhering syrup, which is all driven
off and carries with it the lime, glucate of lime, and other impurities which were
contained in the masse cuite. The sugar left in the machines will be almost pure
white crystallized sugar. The adhering moisture may, if desired, be removed by
stoving.
The syrup which is driven off from the machines may be put back into the first
jet syrup of the original sugar, or if it does not contain a large proportion of glucate
of lime and colouring matters, it may be added to the water in which the next
batch of sugar is being dissolved for the purpose of refining it according to this
process, or it may be worked up in any other convenient way to recover the sugar
contained in it.
Having thus described the nature of the said Invention of "Improvements in the
Refining of Sugar" as communicated to me by my foreign correspondent, I wish it
to be understood that I do not claim the treatment of raw sugars by means of lime
or carbonic acid, or any other chemical agent, neither do I claim the process de-
scribed in the Specifications of the aforesaid Patents, No. 240, A.D. 1876, and No.
4682, A.D. 1877. Neither do I claim the manufacture of refined sugar of ordinary
quality, that is to say, not white sugar, by either of those processes, or by any other
process without the use of animal charcoal; but what I do claim is the refining of
the certain classes of sugar herein-before referred to without filtration through
animal charcoal by re-dissolving them in water and re-crystallizing the sugar, so as
to make a white sugar therefrom, essentially as herein-before described.
In witness whereof, I, the said Hunter Henry Murdoch, have hereunto set
my hand and seal, this Thirtieth day of November, in the year of our
Lord One thousand eight hundred and seventy-eight.
Witness,
J. BIANCHI,
His Olerk.
H. H. MURDOCH. (L.S.)