Improvements in the Purification of Bi-carbonate of Soda Obtained by the Ammonia-soda Process.
Year: 1888

page_text: Date of Application, 19th June, 1888*
Specification Accepted, 20th July, 1888
COMPLETE SPECIFICATION.
Improvements in the Purification of Bi-carbonate of Soda Obtained
by the Ammonia-soda Process.
I, MILTON ROBERT WOOD of No. 36 Ash Street in the City of Brooklyn in the
State of New York, United States of America, Gentleman, 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:-
Bi-carbonate of soda, in the crude condition in which it is commonly obtained by
the ammonia-soda process, is not suitable for chemical or manufacturing purposes or
domestic use, by reason of the impurities contained therein, consisting generally of
compounds of ammonia, or of impurities inherent in the ammonia originally used."
I have discovered that by taking this crude bi-carbonate of soda, mixing the same
with water, and heating the mixture to a temperature of from 180° to 210° Fah.
under a pressure produce by forcing air into and through it, the bi-carbonate is
purified and rendered fit for all the purposes for which bi-carbonate of soda may
be used.
My invention consists principally in the practical application of the above discovery,
as hereinafter described and claimed, to the purpose of purifying the crude bi-
carbonate.
The invention will be particularly described with reference to the accompanying
drawing, which represents a vertical section of an apparatus which may be employed
in carrying it out.
A designates a vessel of horizontal cylindrical or other form, fitted with a loaded
safety valve a, whereby a proper pressure may be regulated therein, and also fitted
with a rotary agitator B 6.-The said vessel is also furnished with a steam coil or
water coil G for heating the contents, and fitted with a perforated pipe C, which is
connected with the delivery pipe c of a compressor D, the suction pipe d of which has
provision for receiving air or carbonic-acid at pleasure, to be forced through the
perforated pipe C into and through the contents of the vessel A. The coil G is
represented as connected with a pipe e for the supply of hot water or steam for heating
the contents of the vessel, and with a pipe f for cooling the said contents, each of the

page_text: said pipes being fitted with a stop cock, by which it may be closed or opened while the
other is open or closed. The said vessel is also provided with suitable inlet and outlet
valves or gates A¹ A2 for filling and discharging.
To carry out my process, the agitator is first started, and the vessel is then filled to
say about three fourths of its depth, more or less, with a mixture of the crude bi-
carbonate, with sufficient water to give the mass a semi-fluid or cream-like consistency,
and is then closed tightly, and steam or hot water is then introduced from the pipe e
through the coil, to bring the mixture to a temperature of say from 180° to 210° Fah.,
after which I force air through the perforated pipe into and through the mixture,
creating and maintaining a pressure of about thirty five to fifty pounds per square inch
by properly adjusting the load of the safety valve, and allowing the exit of the air as
freely as it enters the vessel. This forced circulation of air, and heating of the vessel,
may be continued for a time, varying according to the quantity of material operated
on, say, from fifteen minutes to three hours.
The air thus forced through the mixture acts as an oxidizing agent upon any
oxidizable matter present therein, and also as an agent for removing and carrying off
any impurities of a volatile nature that may be contained in the bi-carbonate, and
vaporized by the action of the heat and air.
After the purification in the above manner has been completed, the temperature of
the mixture in the vessel is reduced to about the temperature of the atmosphere,
which may be done by shutting off the pipe e from the coil, and opening the pipe f to
admit cold water thereto. After the cooling has been effected, the air may be shut
off from the pump, and carbonic acid be forced through the perforated pipe C, for the
purpose of replacing any carbonic acid that may be driven off from the bi-carbonate
in the purification. This carbonic acid so used may be what has been previously
driven off in the purifying process, or obtained from any other source.
The process having been thus completed, the bicarbonate of soda, free from ammonia,
may be discharged from the vessel A, and the bi-carbonate may afterwards be freed
from the water by any of the known or suitable methods of hydro extraction, to be
dried and prepared as desired for use.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is
1. The within described improvement in the purification of the crude bi-carbonate
of soda obtained by the ammonia-soda process, consisting in mixing said crude bi-
carbonate with sufficient water to make a mixture of a semi fluid or cream-like
consistency, and heating the said mixture to a temperature of about from 180°
to 210° Fah., while it is subjected to pressure by forcing air into and through it,
substantially as herein described, for the expulsion of ammoniacal impurities.
2. The within described improvement in the manufacture of bi-carbonate of soda
by the ammonia soda-process, consisting in mixing the crude bi-carbonate of soda
resulting directly from that process, with sufficient water to make a mixture of a semi-
fluid or cream-like consistency, heating the said mixture to a temperature of about
from 180° to 210° Fah., and while so heated, forcing air into or through it, for the
purpose of expelling the excess of ammoniacal impurities, and afterwards forcing
through it carbonic acid gas, for the purpose of replacing the carbonic acid which may
have been driven off by the air; all substantially as herein described.
Dated this 10th day of June 1888
NEWTON & SON,
Agents for the Applicant..