IMPROVEMENTS IN PURIFYING AND DECOLOURIZING CRUDE NITRIC ACID AND IN APPARATUS THEREFOR
Year: 1884

page_text: and in Apparatus therefor.
18
I JOHN WALLER PRATT of Runcorn in the County of Chester, Technical
Chemist, do hereby declare the nature of my said invention for IMPROVEMENTS
IN PURIFYING AND DECOLOURIZING CRUDE NITRIC ACID AND IN APPARATUS
THEREFOR," to be as follows :—
The crude nitric acid of commerce is usually contaminated with the lower oxides
of nitrogen which communicate to it a deep yellow colour and unfit it for appli-
cation to several particular purposes. The object of the present invention is to
provide, means for removing this yellow colour and other impurities from crude
nitric acid simultaneously and apparatus therefor. The invention consists essentially
in subjecting the acid to the action of a current of dry warm air in the apparatus
and in the manner described below. Generally crude nitric acid is subsequently
boiled to free it from the yellow coloration, loss from breakage of glass retorts and
of acid also cost of fuel cause this method to be an expensive one.
Purification is
effected more economically and expeditiously by the following meaus: A series of
glass or earthenware cylinders of suitable size are arranged in order and fitted
with perforated stoppers carrying pipes bent in such a manner and of such a length
and so connected that a current of gas sent through them may ascend from the
bottom of each vessel to its top, into the next vessel in order and so on through
the series. The pipe connected to the leader of the series is coupled to a liorizontal
metallic cylinder capable of being heated by fire or gas to any required temperature
and this cylinder in its turn is joined to a small tower packed with absorbent
material saturated with strong vitriol. From the exit of the series a pipe leads to
another tower like the one above mentioned. Between each two vessels is a
diminutive but similarly fitted cylinder into which the current of gas can be
switched by means of suitable cocks. To bring this apparatus into operation
a quantity of the crude nitric acid is placed in each cylinder and a current of air
is drawn or forced through the acid by means of a steam or water injector pump
or other means. The temperature of the acid should not be below 60° F and
when the temperature of the atmosphere falls below this amount the current of
air is switched or forced through the warming cylinder already mentioned. In
moist conditious of the atmosphere the tower to which the warming cylinder in

page_text: connected serves to take up the moisture in the air current. That the current of
air in its passage through the apparatus circulates from the contents of one cylinder
into those of the next has been already stated. In its course it oxidizes and also
carries off mechanically the lower oxides of nitrogen. The latter portion of
nitrogen oxides carried off from one vessel would be liable to absorption by the
contents of the next. To prevent this the current of gas is diverted into the
smaller subsidiary vessels intermediate in position and which are filled with water
or strong oil of vitriol to absorb the nitric oxides mechanically carried over. The
acid is allowed to circulate from the exit to the leader end of the series which can
easily be effected by reversing the direction of the air current and forcing or
drawing the acid from one vessel to another. The cylinders are fitted with suitable
taps and syphon tubes so that any suitable precipitant can be added to throw down
the impurities-The current of air applied as described well agitates the acid with
any precipitant, thoroughly frees it from any yellow tinge, and only reduces it
about one degree of twaddels hydrometer in strength.

page_text: Improvements in Purifying and Decolorizing Crude Nitric Acid,
and in Apparatus therefor.
I, JOHN WALLER PRATT of 11 Waterloo Road Runcorn in the County of
Chester Technical Chemist do hereby declare the nature of the said invention for
IMPROVEMENTS IN PURIFYING AND DECOLORIZING CRUDE NITRIC ACID AND IN
APPARATUS THEREFOR and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:-
The crude nitric acid of commerce is usually contaminated with the lower oxides
of nitrogen which communicate to it a deep yellow color and unfit it for appli-
cation to several particular purposes-The object of the presont invention is to
remove this yellow colour and other impurities from crude nitric acid simultaneously
and to provide apparatus therefor.
Crude nitric acid is generally purified by distillation in glass vessels and the
acid is subsequently boiled to free it from the yellow colouration. Breakage of
glass retorts loss of acid and the cost of fuel caused this method to be an expen-
sive one.
Now under my invention I purify acid more economically and expeditiously as
follows.
I draw or force air at the requisite temperature and with the necessary freedom
from moisture through the acid to be purified and decolourised substantially as
hereinafter set forth,
Glass or earthenware Cylinders or Vessels of suitable size are arranged in series
are fitted with perforated stoppers and are connected by pipes passing through the
said stoppers of such a length and so bent that a current of Gas sent through the
series will ascend from the bottom of each vessel to its top, and thence passing
the following vessel of the series. The inlet pipe connected to the first vessel of
the series is coupled to a horizontal metallic Chamber capable of being heated by
fire or Gas to any required temperature and this Cylinder in its turn is joined to a
small tower packed with absorbent material and saturated with strong vitriol-
From the exit of the series a pipe leads to another tower like the one above
mentioned-Between each two vessels is a diminutive but similarly fitted Chamber
into which the current of Gas can be switched by means of suitable taps-To
bring this apparatus into operation a quantity of the crude nitric acid is placed in
each Cylinder or Vessel of the series and a current of air is drawn or forced
through the acid by means of a steam or water Injector a pump or other means.
The temperature of the acid should not be below 60 Fahr and when the tempe-
rature of the atmosphere falls below this amount the current of air is sucked or
forced through the warming Chamber already mentioned.
In moist conditions of the atmosphere the tower to which the warming Cylinder
is connected serves to take up the moisture in the air current.
The air in its passage through the acid in series of Cylinders or Vessels oxidizes
and also carries off mechanically the lower oxides of nitrogen.

page_text: As the latter portion of nitrogen oxides carried off from one vessel would be
liable to reabsortion by the contents of the next the current of Gas is diverted
into the smaller subsidiary Chambers which are filled with water or strong Oil of
Vitriol to absorb the nitric oxides mechanically carried over. The acid is caused
to circulate from the exit to the leader end of the series by reversing the direction
of the air current and forcing or drawing the acid from one Vessel to another―
The Cylinders are fitted with suitable taps and syphon tubes so that any suitable
precipitant can be added to throw down impurities-The current of air applied as
described well agitates the acid with any precipitant, thoroughly frees it from any
yellow tinge and only reduces it about one degree of Twaddles Hydrometer in
strength-In practice I find that the operation is most conveniently carried out in
square hexagonal or octagonal vessels constructed of Yorkshire flag stones secured
together with iron rods and brackets and jointed with India rubber. They are
connected together in series or otherwise and worked substantially as above
described.
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
First. Purifying and decolorizing Crude Nitric Acid by forcing or drawing air
therethrough substantially as herein set forth.
Second. Apparatus constructed as combined substantially as herein set forth for
use in the purification and decolorization of crude nitric Acid.
Third. The purification and decolorization of crude nitric acid by means of the
process and apparatus substantially as herein set forth.
T
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