IMPROVEMENTS IN THE MANUFACTURE OF SULPHURIC ACID
Year: 1879

page_text: LETTERS PATENT to Wilhelm Erdmann Albert Hartmann, of Trafalgar Terrace,
Swansea, in the County of Glamorgan, for the Invention of "IMPROVEMENTS
IN THE MANUFACTURE OF SULPHURIC ACID."
Sealed the 12th September 1879, and dated the 11th July 1879.
PROVISIONAL SPECIFICATION left by the said Wilhelm Erdmann Albert
Hartmann at the Office of the Commissioners of Patents on the 11th July
1879.
WILHELM ERDMANN ALBERT HARTMANN, of Trafalgar Terrace, Swansea, in the
County of Glamorgan. "IMPROVEMENTS IN THE MANUFACTURE OF SULPHURIC
ACID."
This Invention has for its object improvements in the manufacture of sulphuric
acid. At the present time it is usual to concentrate the weak or chamber acid by
evaporation, first, in leaden vessels, and afterwards when a strength is attained at
which the acid acts seriously on lead, in vessels either of earthenware, glass, or
platinum. In any case the vessels employed in the final concentration are expensive
to maintain, and the cost of the operation is considerable. Iron vessels are not
available for evaporating the acid in the state in which it is at present drawn from
the leaden evaporating vessels, as the acid in this state acts upon iron energetically.
Now I have discovered that iron vessels may be employed in the final concentration
with impunity and success, if the acid be first fully charged with sulphate of iron;
this sulphate of iron does not remain in the acid as a permanent impurity, but as
the strength of the acid increases during the evaporation, the iron becomes insoluble
until but a trace is left in the acid. The acid may be charged with the full amount
of iron requisite to protect the iron evaporating vessels in which the concentration
is completed before the commencement of the evaporation in leaden vessels. But
it is better to add sulphate of iron to the acid when the preliminary evaporation is
complete, and then without allowing it to cool to continue the concentration in iron
vessels, until the full strength is attained. I make the requisite addition at the
end of the preliminary evaporation by pouring into the acid a strong solution of
sulphate of iron, until the acid appears slightly turbid or milky from precipitation
of iron salt. As before stated, during the final evaporation, the acid rejects iron
dissolved in it, which is partly deposited in the vessel, and the concentrated acid is

page_text: run off to cool and deposit such portion of the iron salt as may have been left
suspended in it.
In order to collect the acid vapor distilling off from the evaporating vessel, I fit
a leaden dome, or hood over the iron pan, and by chimney draft or by a fan or
Fother exhauster,-I-cause the vapors to be drawn up into the hood. I also provide a
Fgutter-around-the lower edges of the hood. to collect the acid trickling down the
interior of the hood, and conduct it. away so that this acid which is not of full
strength and is free from iron, may not come into contact with any portion of the
iron pan. The dome or hood-may-be-cooled-externally-with-water.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Wilhelm Erdmann Albert Hartmann in the Great Seal Patent Office
on the 9th January 1880.
WILHELM ERDMANN ALBERT HARTMANN, of Trafalgar Terrace, Swansea, in the
County of Glamorgan. "IMPROVEMENTS IN THE MANUFACTURE OF SULPHURIC
ACID."
This Invention has for its object improvements in the manufacture of sulphuric
acid. At the present time it is usual to concentrate the weak or chamber acid by
evaporation, first, in leaden vessels, and afterwards, when a strength is attained at
which the acid acts seriously on lead, in vessels either of earthenware, glass, or
platinum. In any case the vessels employed in the final concentration are expensive
to maintain, and the cost of the operation is considerable. Iron vessels are not
available for evaporating the acid in the state in which it is at present drawn from
the leaden evaporating vessels, as the acid in this state acts upon iron energetically.
Now I have discovered that iron vessels may be employed in the final concentration
with impunity-and-success-if-the-acid-be-first fully charged with sulphate of iron;
this sulphate of iron does not remain in the acid as a permanent impurity, but as
the strength of the acid increases during the evaporation, the iron becomes insoluble
until but a trace is left in the acid. The acid may be charged with the full amount
of iron requisite to protect the iron evaporating vessels in which the concentration
is completed before the commencement of the evaporation in leaden vessels. But it
is better to add sulphate of iron to the acid when the preliminary evaporation is
complete, and then without allowing it to cool to continue the concentration in iron
vessels, until the full strength is attained. I make the requisite addition at the end
of the preliminary evaporation by pouring into the acid a strong solution of
sulphate of iron, until the acid appears slightly turbid or milky from precipitation
of iron salt. As before stated, during the final evaporation, the acid rejects iron
dissolved in it, which is partly deposited in the vessel, and the concentrated acid is
run off to cool and deposit such portion of the iron salt as may have been left
suspended in it. In order to collect the acid vapour distilling off from the evapo-
rating vessel, I fit a leaden dome or hood over the iron pan, and by chimney draft

page_text: or by a fan or other exhauster, I cause the vapours to be drawn up into the hood.
I also provide a gutter around the lower edge of the hood to collect the acid
trickling down the interior of the hood, and' conduct it away so that this acid which
is not of full strength and is free from iron, may not come into contact with any
portion of the iron pan.
The dome or hood may be cooled externally with water.
In order to show how my Invention may be advantageously carried out, I have
illustrated in the annexed Drawing an apparatus suitable for the purpose.
The
The cast iron pan a is set over a fire-place b, so that the flames from the latter
must pass underneath and around it before they escape by the flue c into the culvert
d which is in connection with a chimney. The hot sulphuric acid as it leaves the
lead-pan, and containing about 80 per cent. of oil of vitriol, is conducted into the
pan a in a continuous stream by the shoot or gutter e, which may be of cast iron or
any acid-resisting material, such as platinum, glass, or porcelain. In passing
through this gutter, the hot acid is met by a stream of a concentrated solution of
sulphate of iron or copperas which issues from a tank f through the pipe g.
flow of sulphate solution can be regulated by means of the adjustable valve h. A
coiled steam pipe i serves to keep the contents of the tank f hot. In continuing
its course down the gutter e, the acid becomes mixed with the sulphate of iron
solution, and then drops into the pan a The latter is provided with an overflow
or spout k, and is always kept full of boiling acid up to this overflow, and from this
it results that as a continuous stream of weak acid is introduced into the pan, so a
continuous stream of concentrated acid or oil of vitriol leaves it by the spout /c,
and is conducted by a gutter made of any acid resisting material, such as porcelain
or platinum into any suitable apparatus for cooling and storing it. The plant
shown for this purpose in the Drawing consists of two cast iron vessels m and n,
each having a partition in it which does not reach quite to the bottom of the
vessel, so as to force the acid to take a circuitous route. In these vessels the oil of
vitriol loses much of its heat, and deposits nearly all the insoluble iron salt which
it held suspended, and then passes on to a tank or tanks lined with lead, and
which may contain coils of lead piping through which cold water circulates, in
order to absorb what heat is left in the.acid. On having been thus cooled down to
the temperature of the atmosphere, the oil of vitriol is in a fit condition for
industrial purposes. All the settling and cooling vessels should be closely covered,
partly to keep in acid vapours, and partly to keep out dust and moisture.
In order to collect the acid vapour distilling off from the evaporating vessel a, a
leaden hood o is fitted over it which is strengthened and supported by a skeleton of
wrought iron, which latter of course is also coated entirely with lead so as to
protect it against the acid fumes. To prevent the heat from the rim of the pan a
reaching the lower edge of the hood o and there melting the lead, a ring of loosely
placed and well glazed bricks p is interposed. Such weak acid as is condensing on
the inside of the hood is collected by the gutter 9 which is attached to the lower
edge of the hood, and from there conducted by a pipe (not shown) into a suitable
receptacle. A door in the hood gives ready access to the interior of the iron pan,
so that the latter may be cleared from time to time of sediment by means of an
iron ladle. The top of the hood is connected by means of an hydraulic joint to a
leaden pipe 8 which conducts the acid vapour either into an acid chamber, or into
any suitable condenser which in turn is in connection with either a chimney or a
fan or any other exhauster, so as to draw the vapours from the pan and prevent
then from issuing at the lower edge of the hood.
In the arrangement shown, the mixture of weak acid and sulphate of iron
solution as it drops from the gutter e into the much more concentrated acid con-
tained in the pan a becomes, before it can reach the iron of the pan a, a mixture
containing a higher per centage of acid than it held originally. And as the acid
requires less sulphate of iron to saturate it, the more concentrated it is; it follows
that the acid mixture which is run into the iron pan need not be quite saturated,
and yet the pan will be protected against corrosion, as long as sufficient sulphate of

page_text: iron has been added to saturate such acid as comes in actual contact with the iron
pan.
Where it is preferred to work a number of iron pans in series, and run the acid
in succession through all the pans, the weak acid which is run-to-the-first-pan-
should be perfectly saturated with sulphate of iron, or nearly so, as the contents of
the first pan would in such an arrangement, be but slightly more concentrated than
the acid run into it from the lead pan, and would therefore require for saturation
but very little less sulphate of iron than the latter acid. In that case, instead of
effecting the mixing-of acid-and sulphate in the gutter e as above described, I run
acid and sulphate into a small circular lead pan heated in the ordinary way from
below by a fire, and provided with any suitable mechanical arrangement for con-
tinuously agitating and stirring its contents, and only after the mixing of acid-and
sulphate has been thoroughly effected in this lead pan, I pass the acid on to the
iron pans.
Having thus described the nature of my said Invention, and the manner of
performing the same, I would have it understood that I claim as my improvements
in the manufacture of sulphuric acid, the method herein described of conducting the
concentrating process by which I am enabled to dispense with the expensive con-
centrating vessels now in use, to effect the concentration of the acid when its
strength is such that leaden evaporating vessels are no longer available, and
especially I claim continuing the concentration in iron vessels, and causing the acid
to be sufficiently charged with sulphate of iron.
In witness whereof, I, the said Wilhelm Erdmann Albert Hartmann, have
hereunto set my hand and seal, this Sixth day of January, in the year of
our Lord One thousand eight hundred and eighty.