Manufacture of Sulphate Glass.
Year: 1896

page_text: Date of Application, 6'h July, 1896
Complete Specification Left, 1st Apr., 1897-Accepted, 12th June, 1897
Manufacture of Sulphate Glass.
I, KARL WILHELM RICHARD GOERISCH of 5, Schützenplatz, Dresden,
Germany, Merchant do hereby declare the nature of this invention to be as
follows:-
Sulphate of soda (calcined sulphate of Glauber's salts) is much used instead of
soda at the present time for making ordinary window and bottle glass, as also for
semi-white hollow glass. As, however, the decomposition of the sulphate by
silicic acid is effected with much more difficulty and more slowly, and also requires
a. higher temperature than that of soda, there is added to the sulphate composition,
coal powder (charcoal or stonecoal, coke) or stone coal tar. By this addition the
sulphate of soda is reduced by the heat to sulphite of soda, which by the silicic
acid is more easily and quickly decomposed under liberation of sulphurous acid.
As it is, however, not possible, even with the employment of the finest powdered
coal and most careful mixing of the glass composition, to distribute the coal so
uniformly that each particle of sulphate at the commencement of smelting
immediately finds the necessary quantity of coal for the reduction, there arises, a
series of drawbacks in both the previous processes for producing sulphate glass.
These are
1. The duration of smelting is considerably prolonged, as a part of the sulphate
escapes reduction and must be directly decomposed by the silicic acid. The thus
escaping sulphuric acid not only acts on the orucible but also more intensely on the
brickwork of the glass furnace, rendering them,useless in a shorter time than is the
case with soda smelting.
2. A no inconsiderable part of the sulphate is in fact neither reduced nor melted,
and forins "gall," which, even if it is completely separated at the surface, still
essentially decreases the gain in pure glass.
Sulphate glass compositions, as experience shews, give the greatest quantity of
gall, which for the most part consists of unmelted sulphate.
3. If on account of the impossibility of a-uniform distribution of the coal, on
the one hand, a part of the sulphate is not reduced; it is, on the other hand
impossible to avoid now and then a too great reduction i.e. the formation of sodium
sulphate. The latter again has a detrimental effect in so far as thereby the
glass takes a yellow brown colour, which can only be fixed by a further addition
of arsenic or red-lead, (Mussprath's Handbuch d. Tech. Chem. IV Aufl., II Band,
Seite 1423).
4. Finally, as stone coal, as also coke, always contains considerable quantities
of iron, even charcoal not being quite free from this metal, which colors the
glass, it is not possible with the aid of these materials to smelt a pure white
sulphate glass.
The process for the production of sulphate glass by the employment of stone
coal tar involves not only a troublesome and costly preparation of the glass.com-
position (mixing of the ingredients with melted tar, forming bricks and hardening),
but also the employment of quite special furnaces--cupola furnaces-for melting
down these bricks. Besides, with the employment of such a great quantity of tar
as is necessary for forming of bricks, as shewn by experience, it is impossible to

page_text: attain a white, or even only semi- white, glass; a brown to black product being
always the result.
All these drawbacks may be avoided, or essentially reduced, by substituting
for the materials hitherto employed for the reduction of the sulphate (viz. charcoal
or stone coal coke and stone coal tar), organic matters free from iron, having a
high degree of disposable hydrogen, and which are either fluid at ordinary
temperature, or melt at a lower temperature than the sulphate, developing gases
and vapours of reducing effect at increased heat. The most specially suitable of
such materials are all mineral, vegetable, and animal oils and fats, solid fats, as
also paraffin, ozocerite, tallows, further, resin, resin oil, and tar oils, fluid and solid
carburetted hydrogens, of high boiling point, of the aromatic order, and derivatives
of the same.
The employment of these materials offers the following advantages:
1. The materials which are fluid at a common temperature admit of a far more
uniform distribution in it on mixing of the glass compositions, therefore coming
into more intimate contact, in every way, with the sulphate to be reduced, than is
attained by the employment of coal or coke.
2. With the employment of such reducing agents as are not fluid at ordinary
temperature, such as paraffin, ozocerite, resin, this uniform distribution, in conse-
quence of their being easily melted, though not taking place till in the furnace,
is still always before the glass forming constituents of the composition begin
to melt.
By this essentially more intimate mixture of the reducing materials, on the one
hand, and by the high degree of disposable hydrogen they contain on the other
hand, a far surer and more perfect reduction of the sulphate is attained, than by
the employment of coal and coke. The duration of the smelting process is there-
fore decreased, the formation of gall substantially diminished, and the crucibles
and furnaces spared.
The reducing agents mentioned, as they are free from iron, afford still a
special advantage, in that they render it possible to make a much purer white
glass.
Dated this 19th day of June 1896
KARL WILHELM RICHARD GOERISCH.
1, KARL WILHELM RICHARD GOERISCH, of 5, Schützenplatz, Dresden,
Germany, Merchant, do hereby declare the nature of this invention and in what
manner the sanie is to be performed, to be particularly described and ascertained
in and by the following statement :-
Sulphate of soda (calcined sulphate of Glauber's salts) is much used instead
of soda at the present time for making ordinary. window and bottle glass as also
for semi-white hollow glass. As, however, the decomposition of the sulphate by
silicic acid is effected with much more difficulty and more slowly, and also requires
a higher temperature than that of soda, there is added to the sulphate composition,
coal powder (charcoal or stonecoal, coke) or stonecoal tar. By this addition the
sulphate of soda is reduced by the heat to sulphite of soda, which by the silicic
acid is more easily and quickly decomposed under liberation of sulphurous acid.
As it is, however, not possible, even with the employment of the finest powdered
coal and most careful mixing of the glass composition, to distribute the coal so
uniformly that each particle of sulphate at the commencement of smelting

page_text: immediately finds the necessary quantity of coal for the reduction, there arises à
series of drawbacks in both the previous processes for producing sulphate glass.
These are:
1. The duration of smelting is considerably prolonged as a part of the sulphate
escapes reduction and must be directly decomposed by the silicic acid. The thus
escaping sulphuric acid not only acts on the crucible but also more intensely on the
brickwork of the glass furuace, rendering them useless in a shorter time than is
the case with soda melting.
2. A not inconsiderable part of the sulphate is in fact neither reduced nor
inelted, and forms "gall," which even if it is completely separated at the surface,
still essentially decreases the gain in pure glass.
Sulphate glass compositions, as experience shews, give the greatest quantity of
gall, which for the most part consists of unmelted sulphate.
3. If on account of the impossibility of a uniform distribution of the coal, on
the one hand a part of the sulphate is not reduced; it is on the other hand,
impossible to avoid now and then a too great reduction i.e. the formation of sodium
sulphate. The latter again has a detrimental effect in so far as thereby the glass
takes a yellow brown colour, which can only be fixed by a further addition of
arsenic or red-lead, (Mussprath's Handbuch d. Tech. Chem. 1V. Aufl., III, Band,
Seite 1423).
4. Finally, as stone coal, as also coke, always contains considerable quantities of
iron, even charcoal not being quite free from this metal, which colors the glass,
it is not possible with the aid of these materials to smelt a pure white sulphate
glass.
The process for the production of sulphate glass by the employment of stonecoal
tar involves not only a troublesome and costly preparation of the glass composition
(mixing of the ingredients with melted tar, forming bricks and hardening), but
also the employment of quite special furnaces-cupola furnaces-for melting down
these bricks. Besides, with the employment of such a great quantity of tar as is
necessary for forming of, bricks, as shewn by experience, it is impossible to attain
a white, or even only semi-white glass; a brown to black product being always
the result.
All these drawbacks may be avoided, or essentially reduced, by substituting for
the materials hitherto employed for the reduction of the sulphate (viz. charcoal
or stonecoal, coke and stonecoal tar), organic matters free from iron, having a
high degree of disposable hydrogen, and which are either fluid at ordinary
temperature, or melt at a lower temperature than the sulphate, developing
gases and vapours of reducing effect at increased heat. The most specially
suitable of such materials are: all mineral, vegetable and animal oils and
fats, solid fats, as also paraffin, ozocerite, tallows, further resin, resin-oil, and tar
oils, fluid and solid carburetted hydrogens, of high boiling point, of the aromatic
order, and derivatives of the same. From one to thirteen parts of these materials
are added to hundred parts of the glass composition.
The employment of these materials offers the following advantages:
1. The materials which are fluid at a common temperature admit of a far more
uniform distribution in it on mixing of the glass compositions, therefore coming
into more intimate contact, in every way, with the sulphate to be reduced, than is
attained by the employinent of coal or coke.
2. With the employment of such reducing agents as are not fluid at ordinary
temperature, such as paraffin, ozocerite, resin, this uniform distribution, in conse-
quence of their being easily melted, though not taking place till in the furnace,
is still always before the glass forming constituents of the composition begin
to melt.
By this essentially more intimate mixture of the reducing materials, on the one
band, and by the high degree of disposable hydrogen they contain on the other
hand, a far surer and more perfect reduction of the sulphate is attained, than by
the employment of coal and coke. The duration of the smelting process is

page_text: therefore decreased, the formation of gall substantially diminished, and the crucibles
and furnaces spared.
The reducing agents mentioned, as they are free from iron, afford still a special
sadvantage, in that they render it possible to make a much purer white glass.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what
I claim is:
Process for making sulphate glass (especially pure white) consisting in the
addition of organic..matters to the glass batch which are either fluid at ordinary
temperature or melt at a lower temperature than the sulphate (sulphate of soda
free of water) of the batch and contain a high degree of disposable hydrogen, as
and for the purpose set forth.
Dated this 30th day of March 1897.
KARL WILHELM RICHARD GOERISCH.