Improvements in the Preparation and Manufacture of Hydro- sulphurous Acid and Hydrosulphites.
Year: 1898

page_text: Date of Application, 7th Oct., 1898
Complete Specification Left, 7th July, 1899-Accepted, 2nd Sept.,
1899
PROVISIONAL SPECIFICATION.
Improvements in the Preparation and Manufacture of Hydro-
sulphurous Acid and Hydrosulphites.
I, JACOB GROSSMANN, of Harpurhey Chemical Works, Manchester, in the County
of Lancaster, Manufacturing Chemist, do hereby declare the nature of this
invention to be as follows:-
I have found that there is a number of insoluble or slightly soluble com-
pounds of hydrosulphurous acid which are comparatively stable. Such a one
is e.g. the neutral or basic lime compound which may be obtained by double
decomposition of what is now considered as the neutral or alkaline hydrosulphite
of soda and a suitable soluble calcium salt, such as calcium chloride, when nine-
tenths or more of the hydrosulphite in solution is precipitated. Other analo-
gous hydrosulphites may be prepared in a manner similar to this or to any of
the following examples. An insoluble compound of hydrosulphurous acid is e.g.
also precipitated by means of lime from a solution of sulphurous acid which
has been treated with zinc or any other suitable reducing metal; in this case a
double compound of the metal with lime seems to be precipitated. A good pro-
duct is produced as follows. Sulphite of lime or a mixture of sulphite and bisul-
phite of lime is mixed in a closed vessel with the requisite quantity of zinc
powder or other suitable metallic reducer and water, and agitated at a tempera-
ture preferably not exceeding 120° F, whilst a quantity of dilute sulphuric acid,
far short of that necessary to liberate all the sulphurous acid, is gradually and
slowly run into it and enters at the bottom of the vessel. The best proportions
of these ingredients are found by careful experiment and depend on dilution,
temperature, time, and the form of apparatus. When it has been ascertained
by testing that the best practical yield of hydrosulphite has been obtained, milk
of lime is added in suitable quantity when nearly all the hydrosulphite is thrown
down, and may be pressed or otherwise concentrated and as much as possible
freed from water. The acid hydrosulphite may be separated from sulphite of
lime and other useless insoluble matters by filtration before adding lime.
Other suitable sulphites besides calcium sulphite may be used; also other
suitable substances instead of lime for neutralizing and converting the acid salts
into the insoluble normal or basic salts or into analogous double compounds.
Calcium hydrosulphite or the analogous compounds or double salts may be
converted into hydrosulphite of soda, potash, or other soluble salts by treating
them with carbonates, bicarbonates, sulphates, sulphites of the alkalis or of
ammonia, or other suitable soluble salts.
The alkalinity of the insoluble compound may be neutralized by suitable
means.
Hydrosulphurous acid or acid salts may be prepared from the lime compound
by addition of dilute sulphuric acid, or from analogous compounds by other suit-
able acids or acid salts.
Dated thin Cieth dor of October 1808

page_text: Improvements in the Preparation and Manufacture of Hydro-
sulphurous Acid and Hydrosulphites.
I, JACOB GROSSMANN, of Harpurhey Chemical Works, Manchester, in the County
of Lancaster, Manufacturing Chemist, 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: —
Up to the present only easily soluble hydrosulphite compounds such as for
instance sodium hydrosulphite have been known and used in the manufactures
and arts. These have the great disadvantage of being unstable and they can
therefore only be kept for a short time without undergoing partial or total
decomposition. I have succeeded in preparing a series of hydrosulphite com-
pounds which are difficultly soluble or insoluble and which are comparatively
stable. These compounds similar to the soluble hydrosulphites possess strong
reducing properties and can without difficulty be changed into easily soluble
hydrosulphites or hydrosulphurous acid. The following salts may be taken as
representative types of the insoluble hydrosulphite compounds: the neutral or
basic hydrosulphites of the alkaline earths; the corresponding metallic hydro-
sulphites, such as zinc, lead, or similar compounds or double compounds, or
mixtures of the hydrosulphites of the alkaline earths and of metals or metallic
oxides or salts. The most important representative of these new hydrosulphite
compounds is the normal calcium hydrosulphite either by itself or mixed with
metallic salts or compounds. If for instance the solution of a neutral or alka-
line sodium hydrosulphite be mixed with a suitable soluble calcium salt such
as calcium chloride or with a mixture of calcium chloride and a little milk of
lime, the difficultly soluble hydrosulphite of calcium is precipitated. Similar
analogous compounds may be prepared by double decomposition or by treating
hydrosulphurous acid with an excess of lime; in which case the calcium hydro-
sulphite is precipitated.
In order to prepare hydrosulphite of calcium I proceed as follows:-200 lbs.
of a calcium sulphite paste which contains about 16 lbs. sulphurous acid are
placed in a suitable vessel fitted with an agitator and means of regulating the
temperature and heated to about 30° C; about 11 lbs. zinc dust are added to
this mass, and then gradually and slowly about 50 to 55 lbs. of sulphuric acid
of 1225 specific gravity are added. The total time for the addition of the
sulphuric acid should be about two hours. The mass is agitated for a further
three quarters of an hour at about 35° C, and filtered from the insoluble residue
which is washed with water. The filtrate which contains the soluble acid hydro-
sulphite is agitated with milk of lime containing about 17 lbs. CaO until the
liquid part only shows about 20 Twaddle or less which is ascertained by occa-
sionally filtering a small sample. The insoluble part is then separated from
the clear liquor by filtration and represents the normal calcium hydrosulphite.
Instead of filtering the mixture before adding milk of lime, the milk of lime
may be added direct; in that case a more impure product is obtained. Other
insoluble compounds may be prepared in similar manner by replacing calcium
sulphite by barium sulphite, zinc sulphite, or similar other sulphites. The milk
of lime may also be replaced by other suitable hydrates or oxides.
In order to prepare the calcium hydrosulphite from sodium hydrosulphite I pro-
ceed as follows: The sodium hydrosulphite solution which may have been
prepared by any of the well known methods and which has been carefully
neutralized by agitating sufficiently long with milk of lime, and been filtered

page_text: from the residue is if necessary made slightly alkaline by the addition of caustic
soda. A solution of calcium chloride is added to it until double decomposition
is completed which can be ascertained by any of the means well known to
chemists and the insoluble hydrosulphite of lime may then be separated from
the liquor in the usual way. Calcium chloride may be replaced by barium
chloride, zinc chloride, or other suitable soluble salts.
The insoluble calcium hydrosulphite or other similar hydrosulphites may again
be converted into the sodium, potassium, or ammonium compounds by double
decomposition .e. by agitation with solutions of suitable soda salts such as bi-
carbonates, carbonates, sulphates, sulphites, and similar compounds of the
alkalis or of ammonia. Hydrosulphurous acid or acid hydrosulphites may also
be prepared from these compounds by means of sulphuric acid or other suitable
acids or suitable acid salts in a manner well known to chemists. And the in-
soluble salts may also be prepared from hydrosulphurous acid by adding to it,
and agitating it with lime, baryta or any other suitable oxide or hydrate.
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:-
Claim 1. The preparation of difficultly soluble or insoluble hydrosulphites by
the action of zinc or other suitable metallic reducing agents and sulphuric acid
on sulphites or bisulphites of lime or other alkaline earths or on a mixture of
sulphites and bisulphites of the alkaline earths and subsequent precipitation of
the insoluble compounds by means of the hydrates of the alkaline earths such
as for instance milk of lime, as described above.
Claim 2. The preparation of difficultly soluble or insoluble hydrosulphites by
the action of zinc or other suitable metallic reducing agents and sulphuric acid
on sulphites or bisulphites of the alkaline earths as per Claim 1, but with this
difference that the acid hydrosulphite formed is filtered from the insoluble
residue before being treated with milk of lime, or other suitable hydrates of the
alkaline earths.
Claim 3. The preparation of the insoluble hydrosulphites from neutral or
slightly alkaline hydrosulphites of the alkalis by double decomposition with
solutions of the chlorides or other suitable salts of the alkaline earths or of
metals with or without addition of the corresponding hydrates or oxides of the
alkaline earths or of other suitable oxides or hydrates.
Claim 4. The preparation of these salts from hydrosulphurous acid by the
addition of hydrates of the alkaline earths or other suitable oxides and hydrates.
Claim 5. The preparation of hydrosulphurous acid, and of acid soluble hydro-
sulphites from the insoluble or difficultly soluble hydrosulphites by the addi-
tion of a suitable acid, such as sulphuric acid in the case of the normal calcium
hydrosulphite, or of suitable acid salts.
TY