ACTURE OF S OF SUM
Year: 1886

page_text: I, THEOPHILE Raynaud, mänúfacturer, of Moustier-sur-Sambre, in the province
of Namur, Belgium, 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 :-
Hyposulphite of soda is obtained by the oxidation of sulphide of sodium through
the action of sulphurous acid, according to the formula
2 Na² S + 3 SO* = S + 2 S O NÅ³ Oº.
.
Three equivalents of sulphurous acid acting upon two equivalents of mono-
sulphide of sodium give two equivalents of hyposulphité of soda and one equivalent
of sulphur.
The principal object of this invention is the dealing with this equivalent 6f
sulphur as I will explain.
The manufacture of hyposulphite of soda comprises four principal operations:
viz, the manufacture of sulphide of sodium, the preparation of the dissolution, the
converting of the monosulphide of sodium into hyposulphite of soda in a liquid
state, the crystallisation of the liquid hyposulphite.
MANUFACTURE OF SULPHIDE OF SODIUM.
;
The sulphide of sodium is obtained by treating sulphate of soda with coal in a
reverberatory furnace. When the product is obtained, it is allowed to run upon
the preceding similar operation in a trench; this product contains not only thono-
sulphide of sodium, but also polysulphides of sodium; carbonate of soda; caustic
soda, a slight quantity of hyposulphite of soda and some sulphate of soda.
I will explain farther on how to convert into monosulphide, and finally into
byposulphite, all the other salts, (except the remaining sulphate of soda); forming
nearly half of the sulphate treated in the reverberatory furnace.
Dissolution: The production of sulphide of sodium being effected by two rever-
beratory furnaces operating each in turn, the product obtained over-night is treated
the next day. The superposed layers formed by the successive operations of the
previous day are taken up, broken into small fragments and thrown into vessels
heated by steam, these vessels forming what I shall call a dissolver, in which the
product undergoes dissolution.
:

page_text: ;
From thence the dissolution at 15° Beaumé, after undergoing a treatment, the
advantages of which I shall presently point out, runs into an inferior vessel or
tank, whence it is conveyed by pumping apparatus into square upright columns
filled with coke in the following manner, viz: In the interior of these columns
are placed, horizontally, at intervals of about 30 inches one above another, wooden
hurdles upon which are placed large pieces of coke, in such a manner however that
the passage of gases may never be obstructed by the accumulation of substances
upon and around these hurdles, which the various chemical reactions taking place
in the columns would eventually produce.
CONVERTING THE SULPHIDE OF SODIUM INTO HYPO'SULPHITE of Soda.
The liquid dissolution introduced by the top of the column then follows a
descending and opposite course to that of sulphurous acid gas, which I now
introduce into the column. This sulphurous acid gas arises from an oven in
which pyrites are burnt and which communicates by means of a channel or
chamber with the lower portion of the square column. I will as much as possible
use pyrites extracted from coal mines, because they are preferable, save when they
contain carbonate of iron.
When the raw dissolution (that is to say, before having as yet undergone the
treatment which is one of the objects of this patent), is pumped into the columns,
it is pumped over and over again through the different columns until it acquires
a slight degree of acidity. In this state it contains hyposulphite, bisulphite,
.sulphite, carbonate, bicarbonate and sulphate of soda, besides sulphur, either in a
state of deposition or suspension.
These various salts would on concentrating, (except the hyposulphite), deposit at
about 34/36° Beaumé and this is one of the great embarassments of the old process
of manufacture, an embarassment to which it is my object to remedy, as I have
stated above.
The dissolution also leaves in the various parts of the apparatus certain earthy
insoluble substances, besides a proportionate quantity of sulphur in a very divided
state.
It is another of my objects to turn this sulphur to utility and to use it, in con-
junction with lime, in improving the raw dissolution and ridding it of those waste
substances I have mentioned.
I have stated that the raw dissolution contained carbonate of soda, caustic soda,
polysulphides of sodium, a little hyposulphite and sulphate of soda. According to
the greater or lesser degree of impurity of the dissolution, I add to it, per cubic
yard of the same from 28 lbs (twenty-eight pounds) to 38 lbs (thirty-eight pounds)
of slacklime into the dissolver which is heated by steam. The whole of the
carbonate of soda is converted into caustic soda, a part of which forms mono-
sulphide of sodium and a little hyposulphite together with polysulphides.
The main result would be caustic soda, sulphur not being added, but the sulphur
deposited in the chambers and in the tank comes into use and acts upon the
remaining caustic soda.
The liquid dissolution being thus rid beforehand of the impuro salts I have
mentioned, is taken from the collecting tank and conveyed into the first of a series
of three boilers, the first of which I will call the neutralising, the second, the
preparing, and the third, the concentrating.
The slight acidity of the liquid when it reaches the first or neutralising boiler, is
neutralised, with the influence of heat, either by a little carbonate or bicarbonate
of soda, which may happen to remain, or if these are not available, by a slight
addition of the raw dissolution in its sulphurous condition.
The liquid then passes into the preparing boiler, where it is made to reach
35° Beaumé, and from thence into the concentrating boiler, where it is brought
to a proper degree of crystallisation, 45° to 49° Beaumé, according to weather and
season.

page_text: If among the salts precipitated during concentration, there happen to be sulphite
of soda, then sulphur should be added for the next operation in the neutralising
boiler, this sulphur to be taken from the deposits in the chambers or collecting
tank.
Crystallisation. The liquid hyposulphite flows thence into crystallisers, whence it
is taken out after a lapse of two days and then placed upon strainers; from there
it is put into drying-stoves, where it is kept until required for packing.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
The treatment, in the manufacture of hyposulphite of soda, of the dissolution of
raw sulphide by caustic lime; that this treatment increases the production by one
third, it facilitates concentration and renders it less costly; that this treatment
enables the sulphate of soda, (deposited during concentration and freed thereby
from all other salts), to be again available for treatment in the reverberatory
furnace.
Dated this twenty-fourth day of September One thousand eight hundred and