Improvements in Sugar-refining.
Year: 1890

page_text: COMPLETE SPECIFICATION.
[Communicated from abroad by Dr. LOTHAR STERNBERG, of Stapleton, New York,
United States of America, Chemist.]
Improvements in Sugar-refining.
I, HENRY HARRIS LAKE, of the firm of Haseltine Lake & Co. Patent Agents,
45 Southampton Buildings, in the County of Middlesex 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 improvement is intended for employment in the art of refining molasses, syrups
and vegetables juices, particularly the syrups produced from sugar cane, which contain
glucoso, and its object is to get rid of the glucose as a preliminary step to the extraction
of the crystallizable sugar, because glucose when present prevents a certain proportion
of sugar from crystallizing and also renders the product impure.
The invention consists in boiling a solution of molasses syrup or vegetable juice of
a density of say, 10° to 15° Baumé, for a period of two hours more or less, after
mixing with such solution a quantity of either caustic lime, caustic strontia, or caustic
baryta equalling in weight, say, fifteen to thirty per cent. of the weight of dry sugar
plus the weight of the glucoso present. By this means the glucose will be decomposed
and the products of such decomposition by combining with the lime, strontia or
baryta, as the case may be, will form first, compounds which remain insoluble so long
as the solution is alkaline and which are immediately separated in a filter press;
secondly, compounds which are precipitated by treating the solution with carbonic
acid in any ordinary blow up and are thus removed, and finally, certain liquid
compounds the presence of which is not injurious because they do not interfere with
the subsequent extraction of the sugar.
Water may be used as a diluent for the molasses, syrup or vegetable juice to be
treated, in such proportions that the solution will not contain more than twenty per cent.
of sugar, or the washing liquids resulting from the various processes of sugar refining
may be used instead of water, as for example the thin washing liquid from the filters
or the so called washing lye resulting from washing the saccharate of lime obtained
by the process of sugar refining described in Letters Patent of the United States
No. 227,521, dated May 15, 1883.
As is well known glucose is readily decomposed, and its products and also
crystallizable sugar, aro capable of forming compounds with lime, strontia or baryla.
This, in the so-called lime process of refining sugar liquids of low grade described in
Letters Patent of the United States No. 270,879, dated May 3, 1881, wherein it is
sought to precipitate the impurities of the sugar by forming them into insoluble
compounds with lime, care is taken to use only a small quantity of lime and to keep
the temperature of the solution under treatment down to 120° F. or under, during
the first step of the process so that the glucose present will not be affected and the
lime compounds will be formed only with the impurities of the sugar.
In the class of processes of refining cane sugar in which large percentages of lime,
strontia or baryta are added to the saccharine solution under conditions which lead to
the formation of either mono or multi-basic saccharates of lime strontia or baryta, as
the case may be, not only is a certain proportion of otherwise crystallizable sugar
prevented from crystallizing by the glucoso which is originally present but the
saccharate thus produced is rendered impure by the inclusion with it of the com-
pounds resulting from the decomposition of the glucose.
Hence the importance of the result secured by the present process in the removal

page_text: of the glucose from the saccharine solution under treatment as the preliminary step
to the subsequent extraction therefrom of the crystallizable sugar by any suitable
method, as for example, by either of the so-called lime or strontia processes.
In the present process even if the glucose is thrown away more than its equivalent
in value is realised from the increased purity of the final product and from the
increase in the yield of the crystallized sugar due to the absence of the glucose which
has been removed by the preliminary treatment of the solution as herein described.
For this preliminary treatment either lime, strontia or baryta may be employed in
the manner herein set forth, but lime is preferred because of its small cost and also
because it does not attack crystallizable sugar so strongly as caustic strontia or caustic
baryta do.
In carrying out the present invention, after the saccharine solution, containing say,
twenty per cent. or less of sugar has been formed, and either before or after the
addition to it of the lime, it is heated to the boiling point.
Either quick lime or hydrate of lime may be employed. The quantity of line will
depend upon the quantity of glucose present in the saccharine solution. It is desirable
that the quantity of lime shall equal in weight, say, fifteen or thirty per cent. of the
weight of sugar plus the weight of the glucose present, so that there will be more than
sufficient lime to decompose all the glucose and form compounds with all the products
of such decompositions.
After the introduction of the line and the almost immediately following decom-
position of the glucose, the solution is kept boiling continuously until the products of
such decomposition, by uniting with the limo, form the herein mentioned compounds.
It has usually been found desirable to continue the boiling for a period of about two
hours, but of course this period can be varied without departing from the invention.
At the conclusion of this treatment the solution will be found to yield a precipitate
consisting in part of the salts of lime resulting from the destruction of the glucose, in
part of any impurities originally contained in the lime employed and possibly in part
of a portion of the lime present.
The solution is then run through a filter press, by which the resulting precipitate
is removed, after which the clear solution is run into vats provided with the devices
commonly known as blow ups and is saturated with carbonic acid until it is only
slightly alkaline. The result of the carbonic acid treatment is that substantially all
the remaining impurities present are precipitated with the resulting carbonate of lime.
Care must be taken not to supersaturate the solution and thereby cause any part of
the precipitate to redissolve.
To this end from two to ten one hundredths of one per cent. of lime must be retained
in the solution. If, however, the carbonization has been carried too far an excess of
lime must be added and the carbonic acid treatment repeated until the solution again
exhibits a merely slight alkaline reaction.
The solution is again run through the filter presses to complete its separation from
the precipitate and will be found upon examination to be free from glucose and from
any of the injurious compounds resulting from the decomposition of the glucose, so
that it may be advantageously subjected to further treatment for the extraction of its
crystallizable sugar.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed as communicated to me
by my foreign correspondent I declare that what I claim is :-
The improvement in the art of refining low grade sugars molasses, syrups ór
vegetables juices containing glucose, herein described which consists in boiling the
saccharine solution under treatment, together with a suitable quantity of lime or its
equivalent and thereby decomposing the glucose present, and then separating the
resulting insoluble glucose compounds by filtration; secondly, in treating the re-
maining solution with acid and precipitating and removing by a second filtration the
resulting lime compounds and the remaining impurities present, preparatory to

page_text: subjecting the solution thus freed from glucose and from injurious compounds
resulting from the decomposing of the glucose, to further treatment for the extraction
of the crystallizable sugar therefrom.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.