IMPROVEMENTS IN REFINING SUGAB
Year: 1856

page_text: PROVISIONAL SPECIFICATION left by Alexander Williams, Anderson at
the Office of the Commissioners of Patents, with his Petition, on the
29th July 1856.
I, ALEXANDER WILLIAMS ANDERSON, of the Island of Trinidad, Inspector of
Schools and Advocate at Law, do hereby declare the nature of the Invention
for "IMPROVEMENTS IN REFINING SUGAB," to be as follows:-
Dissolve sulphate of copper in boiling water, in the proportion of 3 lbs. of
sulphate of copper to one imperial gallon of water; add to the solution
granulated tin until all the copper is precipitated; (it will take about 1 lbs. of
tin to precipitate the copper from a gallon of the solution.) When all the
copper is precipitated, filter; the filtered liquid will be a colorless solution of
sulphate of tin, to be used in sugar refining.
The methods of proceeding may be varied when using the sulphate of tin
in sugar refining, which I purpose to point out; firstly, with lime; and,
secondly, without lime.
First, with lime.-Add to the solution of sugar and water in the blow-up
cistern (which had better be of a density not higher than 20° of Beaume's
saccharometer) slaked lime, chemically termed hydrate of lime, in the pro-
portion of three ounces of lime to every 100 lbs. of sugar in solution; add to it
sulphate of tin as above made, in the proportion of one imperial pint and one
quarter of a pint to every three ounces of the lime added; the sulphate of tin
may be added before the lime. This relative proportion of lime and sulphate of

page_text: 'tin may be slightly diminished or increased, according to the quality of the sugar
to be operated upon; and when the liquid has been brought to the usual degree
of heat, pass through bag filters and beds of granulated animal charcoal. If
the lime be in excess, as it is in the proportions before mentioned, the
sulphuric acid of the sulphate of tin combines with a portion of the lime
with which it forms sulphate of lime or gypsum, leaving the tin which is
separated from the sulphate of tin, as an oxide of tin. This oxide of tin,
or a portion of it, is redissolved by the excess of lime, forming with it a
stannate of lime. This combination between tin acting as an acid and lime
is of a very feeble character, and is soon destroyed by the carbonic acid of
the air, or by the mere presence of organic bodies, for the tin is again soon
thrown down from the stannate of lime as an insoluble oxide of tin; should
the lime be not in excess, but be exactly in proportion to combine with the
sulphuric acid of the sulphate of tin, then sulphate of lime alone will be
formed, and the whole of the tin will be precipitated as an insoluable oxide of
tin. If the sulphate of tin be in excess of the lime, then a part of its sul-
phuric acid will combine with the lime, forming sulphate of lime; the-tin with
which this portion of the sulphuric acid was combined will be precipitated as
an insoluble oxide of tin, and a portion of the sulphate of tin will remain
dissolved in the sugar solution. On filtration through bag filters the sugar
solution is divested of the insoluable gypsum, oxide of tin, albuminous coloring,
and other matters which have been rendered insoluble through the action of
the sulphate of tin; should there be any sulphate of tin or stannate of lime
in the sugar solution, such combination of tin cannot pass through the animal
charcoal, but is decomposed by the action of the animal charcoal.
When not using lime, I add to the solution of sugar in the blow-up cistern
the same proportion of sulphate of tin, and proceed in all respects as above
pointed out when lime is to be used, with the following exceptions:-No lime
is to be added to the saccharine solution. When the sugar solution comes from
the animal charcoal, test a little of it in a wine glass with sulphuretted
hydrogen, to see that there is no tin in solution, and also occasionally with
tincture of litmus, to see that there is no acidity present in the sugar solution:
If the presence of any tin in solution be indicated, then the sugar solution
should be allowed to remain in contact with the animal charcoal till all trace
of tin disappears; and if the period of time for such disappearance of tin
be long (say, exceeding ten minutes), then the charcoal must be re-burned.
If any sulphate of tin were to pass along with the sugar solution from the
charcoal its presence would be shewn by the sugar refusing to crystallize, or
crystallizing imperfectly. It will be advisable also to add occiasonally a few

page_text: drops of tincture of litmus to a wine glass full of liquor running from the.
charcoal filters to see that there is no acidity present, which, however, is not
likely to be the case; should there be any acidity indicated, which is known
by the liquor being reddened by litmus, the charcoal must be cleansed and
reburned. It will be found of great advantage to the animal charcoal now
and then, say, once a week, or once in two weeks, as occasion may suggest, to
pass into it, and allow to remain in contact with it about half an hour, water
acidulated with from two to five per cent. of bydrochloric acid, for the purpose
of dissolving any oxide of tin or other impurities that may be there, and then
freely cleansing it with steam or water till it is quite sweet. By this means
the use of the charcoal will be prolonged, and under any circumstances it will
be found that animal charcoal, in the quantities as used by sugar refiners, will
continue to decompose sulphate of tin in the relative proportion as added to
the sugar solution for a long time without requiring reburning, and by merely
allowing the solution of sugar to remain in contact with the animal charcoal
for five minutes' time; when it refuses longer to perform this function can be
easily ascertained by the test of sulphuretted hydrogen. Instead of using the
sulphate of tin in the liquid state, as above pointed out, the solution of sulphate
of tin may be subjected to evaporation by heat, in which case a solid residuum
will be obtained, consisting of a subsulphate of tin, which may be used in lieu
of the liquid sulphate, in the proportion of five ounces of subsulphate to every
one hundred pounds of sugar; but this subsulphate will be found difficult of
solution in the saccharine liquid, nor will its action in other respects be as good
as the liquid sulphate, so I prefer the liquid sulphate.