Improvements in the Production of Invert Sugar.
Year: 1889

page_text: Date of Application, 19th Oct., 1889
Complete Specification Left, 19th May, 1890-Accepted, 21st June, 1890
PROVISIONAL SPECIFICATION.
Improvements in the Production of Invert Sugar.
We Dr. ALFRED WOHL and Dr. ALEXANDER KOLLREPP both of 104 Chaussee
Strasse Berlin in the Kingdom of Prussia do hereby declare the nature of this
Invention to be as follows:-
This Invention relates to the production of invert sugar by treating saccharose with
acids and heat and it has for its object the direct production of a concentrated syrup
of invert sugar in a rapid and economical manner.
The invention is based on the observation of the following facts discovered by
us viz.
1. The rapidity with which the inversion of the saccharose takes place is, for all
temperatures of inversion up to 95 degrees Centigrade and for all degrees of
concentration of the solution of cane sugar to be inverted up to about 80 per cent. by
weight, dependent solely on the relation of the quantity of acid employed to the
amount of water present that is to say on the degree of concentration of the acid.
Now as a solution of cane sugar at 80 per cent. strength or concentration contains
only about of the quantity of water contained in a solution at 20 per cent. the
quantity of acid required for the complete inversion of a solution at 80 per cent. other
conditions being the same, is consequently only 1 of what would be necessary for a
solution at 20 per cent.
2. For each kind of acid there is a certain very weak degree of concentration at
which it, on being heated for from about half an hour to one hour to about 80 or
95 degrees Centigrade completely inverts cane sugar in a quantity which may be
equal to four times the quantity of the diluted acid and without decomposing or
colouring the invert sugar so obtained.
For a cane sugar solution of 80 per cent. strength for example the necessary
quantities of acid calculated in proportion to the sugar are as follows:-

page_text: corresponding small quantity of any suitable acid for from say about 30 minutes to
one hour at temperatures between about 70 and 95 degrees Centigrade for example.
The quantity of acid employed is so small that it may be allowed to remain in the
product either in a free condition or after being neutralised with a suitable alkaline
salt such as bi-carbonate of soda.
When the saccharose contains more than 0.02 per cent. of potash salts the quantity
of acid employed must be augmented by the addition of a sufficient quantity of acid
to decompose the potash salts taking into consideration the influence of the neutral
salt on its power of inversion and the excess of acid is then removed by precipitation
with carbonate of lime and filtering. We prefer to take so much acid that the quantity
calculated in anhydrous acid is about double the quantity of the potash salt the
quantity being ascertained by special trials with each acid separately.
In order to obtain merely a partial inversion which is sufficient to increase the
crystallising capacity of the syrup the quantity of acid or the duration of the heating
can be reduced to about one half or less on an inversion temperature of about 65 or
70 degrees Centigrade can be employed. For this particular purpose tartaric and
citric acids can be employed with advantage which in accordance with the principles
herein before laid down are enabled to he employed in much smaller quantity than
heretofore.
In case it is not necessary to produce a perfectly colourless syrup the quantities of
acid herein before specified may be increased about five times according to the
colouring of the syrup provided that the taste of the salts is not injurious. But
when hydro bromic or nitric acids are employed care must invariably be taken
to so limit the quantity of acid as to render the syrup perfectly innocuous.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.
COMPLETE SPECIFICATION.
Improvements in the Production of Invert Sugar.
We Dr. ALFRED WOHL and Dr. ALEXANDER KOLLREPP, both of 104 Chaussee
Strasse, Berlin in the kingdom of Prussia, do hereby declare the nature of this inven-
tion 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 production of invert sugar by treating saccharose with
acids and heat and it has for its object the direct production of a concentrated syrup
of invert sugar in a rapid and economical manner.
According to the rules observed for the inversion of cane sugar by mineral acids
the acid has to act upon diluted sugar solutions of from about 15 to 25 per cent.
strength because hitherto solutions of higher concentration have been found to be
inverted with difficulty and incompletely and subjected to decomposition.
The known technical defects in this process consist chiefly in the necessity for sub-
sequent concentration, the danger of partial deterioration and colouring of the product
by this operation and the necessity for the removal from the product of the large
quantities of acid required in the process.
We have discovered that contrarily to the aforesaid rule cane sugar even in a more
highly concentrated form than 30 per cent, solutions can be inverted easily and with-
out decomposition of the product obtained. Our process is based on the following
novel facts.
I. The rapidity of the inversion of the cane sugar in concentrated solution by dilute
mineral acid is within the limits employed by us that is to say with solutions contain-
ing from about 40 to 80 per cent. of sugar at a temperature of inversion of from
about 45 to 105 degrees Centigrade, far less dependent on the proportion of the
quantity of acid to the quantity of sugar present than it is on the quantity of water
present that is to say on the degree of concentration of the inverting acid. Now as

page_text: an 80 per cent. sugar solution contains only as much water for an equal quantity of
sugar as a 20 per cent. solution, the complete inversion of an 80 per cent. solution, if
this action were independent of the excess of sugar, would only require as much
acid in proportion to the sugar as a 20 per cent. solution, if all other conditions are equal,
the concentration of the diluted inverting acid being the same in both cases. Owing
to the retarding influence of the excess of sugar, however, about 2 of the quantity of
acid required for a 20 per cent. solution is actually necessary. For a 60 per cent.
solution about, for a 40 per cent. solution about 1.
II. In the inversion of cane sugar with acids there takes place along with the de-
composition of the saccharose and at a speed increasing with the concentration of the
sugar solution, a reformation of products of condensation of the dextrose and laevulose
and of both one with the other which precedes and accompanies the decomposition and
colouring, and the speed of which increases more rapidly with the concentration of the
acid than does the power of inversion of the latter.
Each acid has a very low degree of concentration at which, when heated for from
about half an hour to one hour to from about 80 to 95 degrees Centigrade it completely
inverts a quantity of cane sugar which may amount to as much as about four times
the quantity of dilute acid employed without decomposing and colouring the invert
sugar formed and so that the above mentioned reformation is reduced to a minimum.
For an 80 per cent. solution of cane sugar for example the quantities of acid calculated
according to the sugar are as follows:-
0.01 0.02 hydrochloric acid (H CI)
0.02 0.03 hydrobromic (H Br)
0.02-0.03 nitric
0.03-0.05 sulphuric
"
"
(H NÓ₂)
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(H. SO.)
(HFI)
(H, P'h O₂)
"
(H₁₂SO₂)
0-05-0-20 hydrofluoric „
0.15-0.25 phosphoric
0.20-0.40 sulphurous
"
The first column of figures (which are approximately in proportion to the equivalent
weights and constants of inversion) indicate the minimum quantity, whilst the second
column gives the maximum quantity with which uncoloured products can be obtained.
If colourless products are not required the quantities of acid may be increased corre-
spondingly to the colour desired up to five times the quantity needful without injuring
the taste of the product. The colouring produced by the excess of acid takes place
the more easily the more the sugar solution is concentrated.
In accordance with the known laws governing the speed of inversion of diluted
sugar solutions regarding the reciprocal dependence on the temperature of inversion,
quantity of acid and duration of heating, our process can be conducted with tempera-
tures lower or higher than from 80 to 95 degrees Centigrade provided that the
quantity of acid be increased or diminished in accordance with the rule herein specified
for the augmentation or reduction of the inversion constants of the inverting
acids, or that the period of heating be lengthened or shortened or that the value of
both the said factors be so modified that the product remains for the same temperature
approximately constant; with the strong acids the inverting action is influenced if
the quantity be reduced to less than 0.01 per cent. of H Cl or other acid owing to the
acid binding action of the small quantity of mineral salts that remains even in the finest
sugar.
The following table is calculated for practical use and gives the time in hours which
is required with the different temperatures of inversion in order to obtain with the
given concentration of the sugar solution and the given quantity of acid an approxi-
mately complete inversion (viz. up to the maximum of the laevo-rotation attainable
with this concentration of sugar).
The figures representing the quantities of acid denote percentage of anhydrous
hydrochloric acid to sugar. With the employment of the other mineral acids the
correspondin quantities must be substituted according to the preceding list.

page_text: In order to manufacture a colourless concentrated and pure tasting syrup of invert
sugar with refined sugar containing not more than 0.03 per cent. of mineral salts or
ashes we proceed in practice as follows with the employment of hydrochloric acid for
example.
One ton of finely ground white sugar is melted at about 95 degrees Centigrade with
2-4 hectolitres of water in a heated and suitably closed pan provided with agitating
mechanism and with a steam jacket or worm of great heating surface. After cutting
off the steam 0.264 kilos 0222 litres of pure concentrated hydrochloric acid
of 1188 specific gravity previously diluted with 10 litres of water are stirred in, and
the temperature is maintained at from about 90 to 80 degrees Centigrade for about
half an hour.
Heating to over 95 degrees Centigrade is to be avoided as far as possible after the
addition of the acid, as under the conditions given condensation and destruction of
laevulose cominence to take place rapidly at about 100 degrees Centigrade giving the
product a yellow colour. The heating may be prolonged at temperatures under
95 degrees as the yellow colour does not begin to appear until after treating for one
hour. With refined sugar perfectly free from mineral salts or acids the inverting can
be accomplished with half the above mentioned quantity of acid by digesting the
material for two hours.
After drawing off, the colourless invert sugar syrup is cooled quickly and then is
ready for immediate use, being a thick syrup containing about 85 per cent. of sugar.
When a quantity of this syrup corresponding to half the normal weight of cane sugar
is dissolved in water to 100 cubic centimeters this solution, observed at a temperature
of 20 degrees Centigrade, displays a laevo-rotation of 12 degrees of the saccharo-
meter. 02035 grammes of the same when tested for invert sugar with Fehling's
solution give 0.2985 Cu. corresponding to 0.1642 grammes of invert sugar. From
the polarisation it is calculated that about 94 per cent. of the cane sugar employed is
inverted and not condensed, or 95.8 per cent. according to the determination by aid of
Fehling's solution.
The syrup contains 0.08 per cent. of free hydrochloric acid which by stirring in a
solution of 0.23 kilos. of bicarbonate of soda or other suitable salt can be converted
into a chloride. The process admits of being worked very quickly as the inversion
can be commenced at a high temperature in order to quickly dissolve the sugar, and

page_text: then be completed by allowing the concentrated solution to cool down to the tem-
perature corresponding to the quantity of acid employed.
When the syrup is to be filtered, the filtering can be facilitated by performing the
nversion with a solution thinner than 70 or 80 per cent. and afterwards evaporating
the filtered solution in vacuo to the desired degree of concentration.
Solutions stronger than the 80 per cent. solution can also be inverted by means of
this process. For instance by raising the temperature of inversion to 110 deg. Cent.
100 parts of sugar to which are added 0·01 per cent. of hydrochloric acid and 8 parts
of water, can be transformed into a tenacious paste which is inverted to the extent
of when digested for one hour.
In place of hydrochloric acid the other mineral acids may be employed in the
like manner in the correspondingly calculated quantities or as hereinbefore specified.
When sulphurous acid is employed, the materials inust be melted in a closed vessel,
and the acid may either be converted into sulphuric acid by oxidation and allowed
to remain in the product in the form of sulphate of sodium or, as is likewise
necessary in the case hydrofluoric acid be used in greater quantities, it may be pre-
cipitated with Ca CO₂. When, with the employment of a low temperature of
inversion or greater dilution, it becomes necessary to augment the quantity of acid
it is preferable to employ hydrochloric acid as even from toper cent. of sodium
chloride in the product does not prejudice the latter either as regards its utility or its
taste.
Sugars richer in mineral salts or ashes require, besides the quantity of acid
needful for the inversion, an addition of hydrochloric acid equal to from about 0.40
to 0.45 of the said mineral salts or such larger quantity of the other mineral acids
as corresponds to their equivalent weights, hydrofluoric acid being calculated as a semi-
basic, sulphuric acid as one and a half basic, and all other acids as uni-basic.
For the conversion of sugars containing over 0.1 per cent. of mineral salts or
ashes it is preferable to employ sulphuric acid, hydrofluoric acid or sulphurous acid,
the constants of inversion of these acids being lowered by the neutral salts so that the
admissible limits of the quantity of the inverting acid can more easily he observed;
the excess of acid being removed by means of precipitation with calcium carbonate
and filtration. For solutions of from 60 to 70 per cent. strength and temperatures
of inversion of from 80 to 95 degrees Cent. the quantity of acid to be employed is
calculated as follows:-
:-
For sulphuric acid, 09 of the mineral salts or ashes
hydrofluoric, 075,
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"
::
"
2"
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For sulphurous acid and phosphoric acid, thrice or twice the quantity of said salts
with sugar containing less than 0.2 per cent. of ashes, one and a half times the
quantity for sugars with a higher percentage of ashes; for temperatures of from 100
to 110 degrees Cent. about of the quantity required with temperatures of from 80
to 95 degrees Cent.
In this case also it is preferable, especially when working with concentrated
solutions, to employ the smallest possible quantities of acid, because in the thick
solution the precipitated calcium-salts form a tenacious mass, and the employment of
large quantities of edulcorating water, for example for dissolving the sugar to be
inverted, has the disadvantage that the invert sugar which it contains readily decom-
poses when heated and thereby imparts a yellow colour to the product. On the other
hand when only a small quantity of sline is to be edulcorated, the edulcorating water
may be fully employed for diluting the acid.
When the process is employed simply for the sake of preventing the crystallisation
of concentrated syrups, the duration of the treatment corresponding to the tem-
perature of inversion and the amount of acid employed should be reduced to from
about one fourth to one third according to the known laws regulating the time
required for the inversion, so as to invert the sugar by about one half.
When operating with this particular object in view citric acid and tartaric acid may
be employed with advantage in the improved process in place of the mineral acids

page_text: herein before specified. We have discovered that with the employment of these weak
organic acids the inversion of concentrated sugar solutions up to any degree of con-
centration takes place not only with great facility but also that the quantity of acid
needed is only from about one fifth to one twelfth of that required in the processes
heretofore employed with said organic acids. When an 80 per cent. sugar solution
is digested for one hour at a temperature of from about 90 to 95 degrees Cent. we
employ, in place of the mineral acids, either tartaric acid in the proportion of 0.045
per cent. of the of sugar to be treated, or citric acid in the proportion of 0.06 per cent.
of the sugar to be treated. Under an inverting temperature of from 100 to 110
degrees Cent. about one third of these quantities of acid will be found sufficient.
When a quantity of the colourless syrup thus obtained corresponding to half the
normal weight of sugar is diluted with water to 100 cubic centi-inetres and observed
at a temperature of 20 degrees Cent. it exhibits a dextro rotation of +170 degrees
of the saccharometer, that is to say, it is half inverted and this is sufficient to prevent
the cane sugar from crystallising out. The inversion may be completed by employing
a temperature of 100-110° C. with the quantity of said organic acids prescribed for
a temperature of 90-95° C., and digesting for an hour.
The syrup obtained according to the methods hereinbefore described may be
employed as a substitute for sugar when it is inconvenient to employ a sweetening
agent in the solid forin or when the peculiar properties, such as milder sweetness
and quickness of fermentation, of invert sugar make its employment desirable as
f. i. for feeding bees in the winter, sweetening spirits and sweet wines or manufacturing
champagne and the like.
In all cases the sodium salt of the acids specified in the quantities hereinbefore
mentioned as necessary for the 80 per cent. solutions with temperature of inversion of
from about 80 to 95 degrees Cent. may be allowed to remain in the product without
prejudice. With regard to the salts of the hydrochloric sulphuric and phosphoric
acids this applies to the quantities proposed to be used according to our process.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that we
claim is:
1. A process for the manufacture of invert sugar consisting in treating sugar
solutions of not less than 10 per cent. or preferably from about 70 to 80 per cent.
strength and at temperatures not under 40 degrees Cent. or preferably between 70 and
95 degrees with such small quantities of said mineral acids as will admit of the latter
being allowed to remain either free or in the form of a soluble salt in the syrup of
invert sugar without prejudice to its utility, substantially as herein before described.
2. The employment of the process specified in the preceding claiming clause in
the treatment of sugars rich in mineral salts or ashes, the amount of acid being
augmented in such proportion as to bring about the decomposition of the said salts,
and the excess of acid when sulphuric, sulphurous, phosphoric and hydrofluoric acids
are employed being removed by precipitation with carbonate of lime and filtration, all
substantially as hereinbefore described.
3. The employment of the process referred to in the first claiming clause for
obtaining an incomplete or partial inversion of concentrated sugar solutions at tem-
peratures higher than 80 degrees Cent. with the aid of small quantities of tartaric
or citric acids as set forth, in order to obtain directly an uncrystallisable syrup, sub-
stantially as herein before described.