Improvements in the Manufacture of Hydrochloric Acid Free from Arsenic.
Year: 1897

page_text: Date of Application, 6th May, 1897
Complete Specification Left, 3rd Feb., 1898-Accepted, 19th Mar., 1898
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Hydrochloric Acid Free from
Arsenic.
We, JOSIAH RIGBY WYLDE, Alkali Manufacturer, JOSIAH WYCKLIFFE KYNASTON,
Analytical Chemist, and THE UNITED ALKALI COMPANY LIMITED, all of G",
Exchange Buildings, Liverpool, in the County of Lancaster, do hereby declare the
nature of this invention to be as follows:-
The object of this invention is to obtain liquid hydrochloric acid free from arsenic
in an economical manner.
The present inventors have discovered that when a suitable mixture of
hydrochloric acid gas, and vapour of water containing arsenic and sulphuric and
sulphurous acids is passed over, or through, a porous, or equivalent, material,
such as coke, under suitable conditions with respect to temperature, the smaller
quantity of the hydrochloric acid gas and steam which condenses during the
passage of the gas through the porous material absorbs the whole, or nearly the
whole, of the arsenic and holds it in solution and the larger quantity of gas after
having been passed over or through the coke or equivalent material is practically
free from arsenic.
if
According to this invention we take the gases technically known as roaster
gas" that is the gases evolved during the calcination process in the manufacture of
sulphate of soda or the gases evolved during the calcination of a mixture of crude
bisulphate of soda (such as nitre cake) with common salt and we cool these gases,
as far as possible, which may be done by passing them through a number of
cooling pipes or the like and then we pass the gases through a chamber containing
a norous or equivalent substance such as coke which chamber we term a "dry
tower to distinguish it from the usual coke condensing tower in which a stream
of liquid meets the ascending gas to condense it.
"
While passing through the said "dry tower" the gaseous mixture containing
arsenic, sulphurous acid and sulphuric acid and a certain amount of steam deposits
always a small amount of liquid acid and thus moistens the coke or equivalent
material. The arsenic is absorbed and dissolved in this small quantity of liquid
acid. The gas leaving this "dry tower" is free from arsenic if the conditions be
suitable, that is, if the temperature be as low as possible. It should not exceed
about 550 Centigrade.
We convey the gas freed from arsenic into the usual condensing tower where the
hydrochloric acid is condensed by meeting a stream of water, or weak acid free
from arsenic. We thus obtain the greater part of the hydrochloric acid as an
aqueous solution free from arsenic.

page_text: COMPLETE SPECIFICATION..
Improvements in the Manufacture of Hydrochloric Acid Free from
Arsenic.
We, JOSIAH RIGBY WYLDE, Alkali Manufacturer, JOSIAH WYCKLIFFE, KYNASTON,
Analytical Chemist, and THE UNITED ALKALI COMPANY LIMITED, all of G",
Exchange Buildings, Liverpool, in the County of Lancaster, 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:-
The object of this invention is to obtain liquid hydrochloric acid free from arsenic
in an economical manner. The present inventors have discovered that when a suit-
able mixture of hydrochloric acid and vapour of water containing arsenic and
sulphuric and sulphurous acids is passed over, or through, a porous or equivalent
material, such as coke under suitable conditions with respect to temperature the
smaller quantity of the hydrochloric acid gas and steam which condenses during
the passage of the gases through the porous material absorbs the whole, or nearly
the whole, of the arsenic and holds it in solution and the larger quantity of gas
after having been passed over or through the coke, or equivalent material, is
practically free from arsenic. According to this invention we take the gases
technically known as roaster gas." (that is the gases evolved during the calcination
process in the manufacture of sulphate of soda) or the gases evolved during the
calcination of a mixture of crude hi-sulphate of soda (such as nitre cake) with
common salt and we cool these gases as far as possible which may be done by
passing them through a number of cooling pipes or the like and then we pass the
gases through a chamber containing a porous or equivalent substance such as
coke which chamber we term a "dry tower" to distinguish it from the usual coke
condensing tower in which a stream of liquid meets the ascending gases to condense
them. Whilst passing through the said "dry tower" the gaseous mixture. con-
taining arsenic, sulphurous acid and sulphuric acid and a certain amount of steam,
deposits always a small amount of liquid acid and thus moistens the coke or
equivalent material. The arsenic is absorbed and dissolved in this small quantity
of liquid acid. The gas leaving this "dry tower" is free from arsenic if the
conditions be suitable. that is if the temperature be as low as possible. It should
not exceed about 55° Centigrade.
We convey the gas freed from arsenic into the usual condensing tower where the
hydrochloric acid is condensed by meeting a stream of water or weak acid free from
arsenic. We thus obtain the greater part of the hydrochloric acid as an aqueous
solution free from arsenic.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is:-
#
*
The process for the manufacture of hydrochloric acid free from arsenic from the
gases evolved during the calcination process in the manufacture of sulphate of
soda, technically known as roaster gas or from the gases evolved during the
calcination of a mixture of bisulphate of soda (nitre cake) and common salt, con-
sisting in first cooling the said gases and then passing them through, or in contact

page_text: with, coke or equivalent material in a "dry tower" in which the arsenic is re-
tained, and thence through a wet tower in which the hydrochloric acid is condeused
substantially as hereinbefore described.
Dated this 3rd day of February 1898.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.