5261 5265.output

* GB785668 (A)
Description: GB785668 (A) ? 1957-10-30
Improvements in the separation of acetylene from gas mixtures
Description of GB785668 (A)
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The EPO does not accept any responsibility for the accuracy of data
and information originating from other authorities than the EPO; in
particular, the EPO does not guarantee that they are complete,
up-to-date or fit for specific purposes.
COMPLETE SPECIFICATION Improvements in the Separation of Acetylene
from Casr Mixtures
We, BADISCHE ANILIN & SODA-FABRIR AKTIENGESELLSCEAFT, a Joint Stock
Company organised under the laws of Germany, of Ludwigshafen/Rhein,
Germany, do hereby declare the invention, for which we pray that a
patent may be granted to us, and the method by which it is to be
performed, to be particularly described in and by the following
statement:-
For the separation of acetylene from gas mixtures, in particular those
which have been obtained by thermal or electrical cracking of
hydrocarbons with or without oxygen, pro cesses are known according to
which the acetylene is washed out from the gas mixture by a solvent.
In order to be able to absorb the largest possible amounts of
acetylene, this washing is carried out under increased pressure. If
the gas is put under pressure, however, difficulties are encountered,
chief among which are the following: black deposits will form on the

suction valves of the compressor and affect the functioning of the
valves after some time; incrustations of more or less dark colour will
form in the cooling devices of the compressor, reduce the cooling
effect and even clog the condenser tubes after some time. These
incrustations can only be removed by mechanical means. According to
our knowledge these incrustations partly consist of polycyclic
hydrocarbons, as for example naphthalene, beta-methylnaphthalene,
acenaphthene, and acenaphthylene. The said shortcomings can be
remedied by subjecting the gas to a pre-wash treatment with a solvent
capable of absorbing the said contaminants. Thus, it has heretofore
already been proposed to strip the gap of diacetylene with a solvent
prior to compression.
Wherever solvents have been used for a prewash of a gas, they have had
to be stripped from the gas separately in order to be re-used in a
cycle.
We have now found that the separation of acetylene can be carried out
in a simpler
nanner while avoiding the said disadvantages
md with only one solvent by working in two
sllges, a smaller amount of the solvent being used in the first stage
at atmospheric pressure or at the pressure at which the gas mixture is
formed or slightly above the same, and a larger amount of the same
solvent being used in the second stage at a higher pressure than in
the first stage. The washing liquids are freed from the absorbed
substances in the usual way by releasing the pressure and degas sing,
preferably at elevated temperature and sub-atmospheric pressure, and
used again for the washing. Since the same solvent is used in both
stages, the working up of the laden washing liquids can be carried out
together so that the process is simplified considerably.
The washing in the two stages is preferably carried out at room
temperature. In the first stage atmospheric or only slightly increased
pressure, for instance up to 1.5 atmospheres, is used. The pressure is
determined by the necessity that the temperature may not fall below
the dew point of the said polycyclic hydrocarbons. A pressure inferior
to one atmosphere absolute is also applicable, but a pressure below
atmospheric pressure will preferably be avoided in practical operation
in view of sucking in air and having to compress a mixture of
acetylene and oxygen which might cause danger of explosion. If the
acetylenecontaining gas has been obtained by a process which operates
under pressure, the washing can be carried out at this pressure or a
slightly higher pressure. In the second stage the pressure is higher;
it may lie for example between about 8 and 30 atmospheres. The lower
pressure limit is mainly dependent upan economic considerations, the
quantities of solvent to be circulatedGbeing too large when employing

too low a pressure. The upper pressure limit is determined by the
necessity for the partial pressure of the acetylene being not higher
than that to which acetylene can be compressed without danger of
explosion. The pressure limits, as a result, are also determined by
the composition of the gas mixture, i.e. by the percentage of
acetylenes.
The amount of washing liquid which is necessary in the first stage is
only a small frac tion of the washing liquid which is used in the main
washing in the second stage. As a rule, for the preliminary washing in
the first stage, less than 2% of the amount of washing agent used in
the second stage is sufficient. The amount of solvent used in the
first stage is preferably an amount just sufficient to recover
substances harmful to high-pressure operation while absorbing only a
small quantity of acetylene and a minor part of the diacetylene
present in the gas mixture. Optimum quantities of solvent can be
readily determined by simple experimentation. To obviate the said
difficulties the said polycyclic hydrocarbons which melt at a
temperature lying above that of the cooling water used; need only be
washed out to such an extent that the temperature under the prevailing
pressure conditions, does not fall below the dew point
Solvents suitable in the practice of our invention are such organic
solvents with a boiling point higher, for example, than 1500 C.
and a high solvent power for acetylene, as are stable thermally and at
least partially miscible with water, as for example butyrolactone and
N-methylpyrrolidone.
The separation of the acetylene from the laden washing liquid is
effected in the usual way by releasing the pressure, for example to
atmospheric pressure, and also by gassing out with the aid of pure
acetylene, for example acetylene obtained from the process, and if
desired by further gassing out at elevated temperature and/or at
reduced pressure. It is advantageous to use several stages when
degassing and to remove first the gases which have a lower solubility
coefficient than acetylene.
The washing liquid freed from acetylene is returned to the two washing
stages. It is preferable to branch off a small portion and to remove
therefrom, for example by distillation, the constituents absorbed
thereby which are not separable by degassing. The washing liquid thus
purified, if desired together with a part of the liquid which has only
been degassed, is used for the preliminary washing in the first stage.
The washing liquid withdrawn from the first stage, without previous
gassing, can also be freed by distillation from the constituents not
separable by degassing and returned to the two washing stages either
alone or together with degassed washing liquid.
The invention will now be described with reference to the accompanying

drawings which illustrate diagrammatically by way of example three
embodiments of the process according to this invention. Similar parts
are designated by similar letters in each of the drawings.
Referring to Figure 1, an acetylene-containing gas mixture is led at
atmospheric pressure through a pipe A into a washing tower B into
which a solvent for acetylene is charged at the top through a pipe C.
The solvent laden with impurities and some acetylene leaves the
washing tower B through a pipe R which conducts it toward the
degassing tower 0.
The preliminary purified gas mixture is led from the tower B through a
pipe D to a compressor Z from which it passes into a washing tower E.
The bulk of the solvent for the acetylene is supplied to this tower
through a pipe F. The laden washing liquid is withdrawn through a pipe
H and led into a rectification tower I while being released from
pressure through an expansion valve V. In this tower there takes place
a separation of the gases dissolved in the washing liquid into pure
acetylene which is withdrawn through a pipe M and gases with a smaller
solubility coefficient than acetylene which escape through a pipe L
and are supplied to the compressor Z.
The washing liquid leaves the tower I through a pipe N and, after it
has been combined with the washing liquid flowing from the preliminary
washing tower B through the pipe R, passes to the degassing tower 0.
From this the residual gas escapes through a pipe K and is led into
the lower part of the rectification tower I. The constituents which
have a higher solubility coefficient than acetylene escape from the
degassing tower 0 through a pipe P.
The washing liquid freed from acetylene and other readily soluble
constituents leaves the degassing tower 0 through a pipe Q and passes
through pipes F and C to the washing towers
E and B.
Figure 2 shows the same process but in which a part of the degassed
washing liquid, leaving the degassing tower 0, is branched off, freed
in the vessel S from substances having a low vapour pressure which
therefore have not been removed by the degassing (these are withdrawn
through a pipe U) and supplied through pipes T and C to the first
washing stage B. The portion of the washing liquid which has only been
degassed and which leaves the degassing tower 0 through the pipe Q, is
led to the second washing stage E and partly to the first washing
stage B.
According to Figure 3, the washing liquid laden in the first washing
stage is led through the pipe R, if desired together with a portion of
the washing liquid leaving the degassing tower 0, to the treatment
plant S and thence, after separation of the constituents not removable
by gassing, to the washing stages E and

B together with the washing liquid which has only been degassed from
the degassing tower 0.
The following examples, given with reference to Figure 2, will further
illustrate this invention but the invention is not restricted to these
example. Parts are parts by weight unless otherwise specified.
EXAMPLE 1.
By incomplete combustion of methane a gs mixture is produced having
the following avlr- age composition expressed as percentages by
volume:
Acetylene - - - - 8.15
C3H4-hydrocarbons - - 0.1
Diacetylene - - - - 0.12
Benzene - - - - - 0.03
Ethylene - - - - 0.3
Methane - - - - 4.1
Carbon dioxide - - - 3.5
Oxygen - - - - - 0.1
Carbon monoxide - - 26.0
Hydrogen - - - - 56.7
Nitrogen plus argon - - 0.9
In addition the mixture contains the following contaminants in grams
per cubic metre:
Phenylacetylene - - - 0.11
Naphthalene - - - 020
Acenaphthene - - - 0.04
Acenaphthylene - - - 0.06
Using a plant system as illustrated in Figure 2 of the accompanying
diagrammatic drawing 100 cubic metres of the said gas is passed
through line A into the pre-washer B at a pressure of 1.1 atmospheres
absolute and a temperature of 19 C., 2 kilograms of butyrolactone
being simultaneously fed in through line
C. From line D a gas of the following average composition (expressed
as percentages by volume) is withdrawn:
Diacetylene - - - - 0.11
Benzene - - - - 0.02
Methane - - - - 4.1
Oxygen - - - - - 0.1
Hydrogen - - - - 56.73

In addition the gas contains the following substances in grams per
cubic metre : -
Phenylacetylene - - - 0.09
Naphthalene circa - - 0.02
Acenaphthene - - - < 0.01
Acenaphthylene - - - < 0.01
As a result, about 10% of diacetylene, about 2030 % of benzene and
phenylacetylene, about 90% of naphthalene and at least 9()% of
acenaphthene and acenaphthylene have been removed.
The pre-washed gas is compressed to a pressure of 9 atmospheres
absolute in a compressor
Z. The compressor and the condensers attached to it remain perfectly
dean, apart from a faint film of carbon black, even after operation
for weeks, while in the absence of a pre-wash stage deposits of carbon
black and naphthalene will form after a few hours in the compressor
and especially in the condensers resulting in a decrease in the
efficiency of the compressor and the cooling effect of the condensers
after a two weeks' operation. These deposits can only be removed by
mechanical means
The gas mixture compressed to 9 atmospheres absolute then passes to
the scrubber
E into which 1150 kilograms of butyrolactone are fed overhead through
line F at a temperature of 23 C. Through line G 91 cubic metres of a
gas having the following average composition in percentages by volume
are with drawn:
Methane - - - - 4.5
Oxygen - - - - - 0.1
Hydrogen - - - - 61.8
No polycyclic hydrocarbons and higher acety lenes can be identified.
The washing agent laden with acetylene and part of the other
constituents contained in the crude gas leaves the tower E through the
pipe
H and passes into the rectification tower I and thence through the
pipe N into the degassing tower O where by heating to 100 C. and
reducing the pressure to 0.2 atmosphere the dissolved gases are set
free. The liberated gases pass through the pipe K into the lower end
of the rectification column I in which they flow in countercurrent to
the solvent. A part of the acetylene with the gases expelled from the
solution leave the tower I through the pipe L and are supplied to the

suction side of the compressor Z. 7.9 cubic metres of acetylene which
contains about 0.1% of C,H4-hydrocarbons less than .1% of carbon
dioxide, less than 0.02% of diacetylene and less than 0.01% of
benzene, are withdrawn through the pipe M.
No polycyclic hydrocarbons can be identified
The gas constituents of better solubility than acetylene escape from
the degassing tower 0 through the pipe P. In the said gas, in addition
to small quantities of acetylene, the following components are
detected:
Methylacetylene
Relatively large proportions of :
Diacetylene,
Phenylacetylene,
Naphthalene,
Acenaphthene, and Acenaphthylene.
The solvent which has been degassed in the degas sing tower O is for
the most part returned to the washer B through the pipe Q while a
smaller partial stream is subjected to a distillation in the tower S.
The solvent distilled over, after condensation and cooling, is
returned through the pipe T to the tower B and if desired supplemented
by solvent from the pipe Q. The impurities incapable of distillation
in the tower S are withdrawn through the pipe U.
EXAMPLE 2.
By incomplete combustion of methane a gas mixture of the following
average composition in percentages by volume is produced :
Acetylene - - - - - 8.65
C3H4-hydrocarbons - - - 0.1
Diacetylene - - - - - 0.17
Benzene - - - - - 0.08
Ethylene - - - - - 0.3
Methane - - - - - 5.2
Carbon dioxide - - - - 3.6
Oxygen - - - - - - 0.12
Carbon monoxide - - - - 24.9
Hydrogen - - - - - 55.8
Nitrogen plus argon - - - 1.1
per cubic metre:
Phenylacetylene - - - - 0.21
Naphthalene - - - - - 0.36
Acenaphthene - - - - 0.10
Acenaphthylene - - - - 0.27
Pyrene - - - - - - 0.001
Using a plant system as illustrated in

Figure 2, 100 cubic metres of the said gas are passed through line A
to the pre-washer B at a pressure of 1.05 atmospheres absolute and a
temperature of 25 C., 4.9 kilograms of Nmerhylpyrrolidone being
supplied through line C. The gas withdrawn from line D has the
following average composition in percentages by volume:
Acetylene - - - - - 8.63
Diacetylene - - - - - 0.11
Benzene - - - - - - 0.06
Ethylene - - - - - 0.3
Methane - - - - - 5.2
Carbon dioxide - - - - 3.6
Oxygen - - - - - - 0.1
Carbon monoxide - - - - 24.9
Hydrogen - - - - - 55.9
Nitrogen plus argon - - - 1.1
per cubic metre:
Phenylacetylene - - - - 0.15
Naphthalene - - - - - 0.03
Acenaphthene - - - - < 0.01
Acenaphthylene - - - - < 0.01
Pyrene - - - - - - not
identifiable
As a result, about 30% of diacetylene, of benzene and of
phenylacetylene and about 90% of naphthalene, of acenaphthene and of
acenaphthylene have been removed.
The gas mixture is then compressed to 13 atmospheres absolute in the
compressor Z.
Both the compressor and the condensers attached thereto, apart from a
faint film of carbon black, remain perfectly clean even after an
operation for weeks.
The compressed gas mixture is then scrubbed with 450 kilograms of
N-methylpyrrolidone in the scrubber E. The result is substantially the
same as that obtained in
Example 1, except that 8.4 cubic metres of acetylene with about 0.1%
of C,H4-hydrocarbons, less than 0.1% of carbon dioxide, less than
0.01% of diacetylene and less than 0.005 O of benzene are obtained.
Specification No. 689,444 claims a process for the removal of
acetylene from a gaseous mixture containing the same which consists in
treating the mixture with an N-alkyl-1-pyrrolidone the alkyl radical
of which is a-saturated hydrocarbon radical not containing more than 3
carbon atoms to absorb the acetylene.
What we claim is: -

1. An improved process for the separation of acetylene from a gas
mixture containing acetylene and obtained by cracking hydrocarbons
which comprises washing said gas mixture in a first stage with an
amount of solvent and at a sufficiently low pressure such that only a
small quantity of acetylene and diacetylene is absorbed, and washing
the gas from the first stage in a second stage with a larger amount of
the same solvent and at a higher pressure than in the first stage so
as to recover acetylene.
2. A process as claimed in Claim 1 wherein the pressure in the first
stage is between about atmospheric to 1.5 atmospheres and the pressure
in the second stage is between about 8 to 30 atmospheres.
3. A process as claimed in Claim 1 wherein the pressure in the first
stage is of the same range as the pressure under which the
acetylene-containing gas mixture has been obtained.
4. A process as claimed in any of Claims 1 to 3 wherein the amount of
solvent employed in the first stage is less than 2 .. -' of the amount
of solvent employed in the second stage.
5. A process as claimed in any of Claims 1 to 4 wherein the solvent
employed is butyrolactone.
employed is methylpyrrolidone.
leaving each stage is freed from absorbed substances and reused for
the washings.
leaving the second stage is freed from acetylene and is then combined
with solvent from the first stage and the combined solvents are freed
from other absorbed substances and reused for the washings.
9. A process as claimed in Claim 8 wherein the combined solvents from
each stage are subjected to a degassing, at least part of the degassed
solvent returned to the second stage washing, the remaining degassed
solvent distilled to remove absorbed constituents not separable by
degassing, and the distilled solvent returned to the first stage.
10. A process as claimed in Claim 1 which also comprises rectifying
the solvent from the second stage to free pure acetylene, degassing
the rectified solvent from the second stage, distilling at least part
of the solvent from at least one of the two stages to free absorbed
constituents not separable by gassing, and reusing
* GB785669 (A)

Description: GB785669 (A) ? 1957-10-30
Additive for high altitude brush
PATENT SPECIFICATION
7859,669 Date of Application and filing Complete Specification: March
6, 1956.
No 6943/56.
Application made in United States of America on March 8, 1955.
Complete Specification Published: Oct 30 1957.
Index at acceptance:-Class 35, A 2 B 3.
International Classification:-HO 2 k.
COMPLETE SPECIFICATION
Additive for High Altitude Brush We, UNION CARBIDE CORPORATION
(formerly Union Carbide and Carbon Corporation), of 30, East 42nd
Street, New York, State of New York, United States of America, a
Corporation organised under the laws of the State of New York, United
States of Amnerica, (Assignee of DIMITER RAMADANOFF), do hereby
declare the invention, for which we pray that a patent may be granted
to us, and the method by which it is to be performed, to be
particularly described in and by the following statement: -
This invention relates to brushes for the supply of electric current,
and more particularly concerns long wearing commutator brushes which
are suitable for use at conditions encountered at both sea level and
at high altitudes.
For sea level and high altitude applications, high altitude metal
graphite brushes, such as high altitude copper-graphite brushes, have
several desirable properties At a given current density and rubbing
speed, the coppergraphite brushes generally operate with a lower
icontact voltage drop and a lower temperature at a given load than
high altitude electrographitic brushes The brush stock has low

electrical resistivity, which is helpful in cutting down power losses
But coppergraphite brushes also have some disadvantages.
They operate with high coefficient of friction than electrographitic
brushes, and are sensitive to commutator or ring eccentricity
Sometimes the combination of these two factors may intensify sparking,
and even cause under some conditions, the release of small streamers
at the trailing edges This may lead to undesirable ring wear
Consequently, the conventional copper-graphite brushes are usually
limited in their application.
The conventional high altitude metal graphite brush containing
approximately 25 per cent to 75 per cent copper, 10 per cent to, per
cent graphite, 5 per cent to 25 per cent barium fluoride and a small
amount of binder material has some unusually good properties as a high
altitude brush For instance, a brush having a composition of about 75
per cent copper, 15 per cent graphite and 10 per cent barium fluoride
has an electrical resistivity of 0.000008 ohms per cubic inch Its
contact voltage drop of 0 35 volts with a current density of 180
amperes per square inch at an altitude of 40,000 feet above sea level
is one of the lowest on record Such a brush grade has proven to
commutate very well, and due to its barium fluoride content, has
resisted dusting at altitudes up to 70,000 feet It is generally known
that other alkali earth salts and oxides and those of the rare earth
family also impart resistance to dusting under high altitude
conditions However, a weakness possessed by this copper graphite brush
is representative of the behavior of brushes falling within the above
composition range is its short life under some conditions It has an
average brush life of only 975 hours per inch at sea level, and, 510
hours per inch under simulated altitude conditions, at 40,000 feet.
According to the present invention a coppergraphite electrical contact
brush having improved wear resistance comprises a coppergraphite
mixture containing 25 per icent to 75 per cent by weight of copper, 10
per cent to per cent gralphite and 5 per cent to 25 per cent by weight
of barium fluoride, and an additive of boron nitride or an additive
mixture of boron nitride with one or more of the following: lead,
silver, or a coumatone indene resin, such additive or additive mixture
being present in an amount between 0 5 per cent and 15 0 per cent by
weight of the coppergraphite mixture.
Table I lists the components of the preferred additive embodying the
principles of the invention in percentage by weight of the
copper-graphite mixture All percentage figures appearing anywhere in
the description relate to percentages by weight.
lPrice 3 s 6 d l 2785,669 TABLE I
Composition, Per Cent Broad Range Preferred Range 1 Boron Nitride up
to 5 % 0 5 % to 1 5 % 2 Silver up to 10 % 4 % to 6 % Boron Nitride up

to 5 % 0 5 % to 1 5 % 3 Lead up to 10 % 4 % to 6 % Boron Nitride up to
5 % 0 5 % to 1 5 % 4 Boron Nitride up to 5 % 0 5 % to 1 5 % Silver up
to 10 % 4 % to 6 % Coumarone Indene Resin up to 5 % 2 % to 3 % The
invention will be more fully understood from the following detailed
description of typical examples of its use for prolonged brush life at
sea level or high altitude iconditions.
EXAMPLE I.
The composition of a copper-graphite mixture containing 75 parts
copper, 15 parts graphite, 10 parts barium fluoride and a small amount
of binder material was modified by adding to it boron nitride powder
in an amount equal to 1 per cent by weight of the mixture The said
ingredients were then well mixed and molded at a pressure of 15 tons
per square inch to a block of suitable size for making a commutator
brush The blozk was then baked at 900 C by suitable heating means for
a period sufficient to impart known and inherent brush
characteristics.
Table II, which follows the examples, sets forth the conditions and
results of a number of typical tests wherein the brush was tested at
sea level conditions, and at an altitude of 40,000 feet In these tests
the brushes were subjected to a current density of 60 amperes per
square inch at sea level, and current densities of 120 and 180 amperes
per square inch at 40,000 feet altitude.
EXAMPLE II.
To a mixture having the composition of Example I containing 1 per cent
boron nitride, was added 5 per cent metallic silver powyder.
The mixture was formed into the shape -cif a commutator brush, and
baked in the manner described in Example I to impart to it the
requisite brush characteristics Table II sets forth the conditions and
results of a number of typical tests.
EXAMPLE III.
To a mixture having the composition, of Example II containing 1 per
cent boron nitride and 5 per cent silver, there was added coumarone
indene resin in an amount equal to about 2 5 per cent of the
metal-graphite mixture The mixture was then formed and baked in the
manner previously described.
Table II sets forth the conditions and results of a number of typical
tests.
The procedure used for testing the brushes in Examples I, II and III
at sea level consisted in applying the brush to a machine having an
operating speed of 6500 revolutions per minute and a rubbing speed of
5100 feet per minute A brush spring pressure of 7 1 pounds per square
inch was used The current flow through the brush was adjusted to 40
amperes or a current density of about 120 amperes per square inch
Tests were conducted in room air for a total of 20 hours or more

During that time readings were taken of contact voltage drop, brush
temperature, and coefficient of friction At the end of the tests brush
length was measured and brush life in hours per inch of wear was
calculated All altitude tests were made on rotating copper rings.
In similar fashion, a number of other brushes were tested, the
compositions, operating conditions and properties being shown in Table
1 I.
Additive 785,669 TABLE II
Composition Cu C Ba F 2 BN Pb Ag Resin A 75 15 10 B 75 15 10 1 C 75 15
10 1 5 D 75 15 10 1 5 2 5 E 45 45 10 F 45 45 10 1 5 G 45 45 10 1 5
Conventional High Altitude Brush Composition Operating Properties
Current Brush Coef of Density Contact Brush Life Friction Altitude
Amps Per Drop Temp Hrs Per Against Brush in Feet Sq Ft Volts OC Inch
Copper A 0 60 0 27 83 975 0 09 40,000 120-180 0 24-0 38 70-89 510 B 0
60 0 20 91 1470 0 11 40,000 120-180 0 38-0 48 72-102 807 C 0 60 0 13
99 1305 0 12 40,000 120-180 0 42-0 59 79-128 890 D 0 60 0 23 88 2360 0
07 40,000 120-180 0 54-0 76 106-147 930 E 0 120 0 85 143 2960 0 24
40,000 120 0 58 179 620 F 0 120 1 24 126 3616 0 13 40,000 120 1 00 158
2260 G 0 120 1 32 139 5790 0 15 40,000 120 1 12 185 2380 Conventional
Brush Composition
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* 5.8.23.4; 93p
* GB785670 (A)
Description: GB785670 (A) ? 1957-10-30
Improvements in or relating to chemical compounds for use as x-ray
diagnostic agentsand to processes for their preparation

COMPLETE SPECIFICATION Improvements in or relating to Chemical
Comlrounds for use as
X-Ray Diagnostic Agents' and to processes for
their preparation
We, SCHERING CORPORATION, of 60, Orange
Street, Bloomfield, New Jersey, United States of America, a
corporation organized under the laws of the State of New Jersey,
United Srates of America, do hereby declare the invention, for which
we pray that a patent may be granted to us, and the method by which it
is to be performed, to be particularly described in and by the
following statement:
This invention relates to a new group of halogenated compounds which
have important
X-ray contrast properties. More particularly, this invention relates
to new 5-acylaminopoly- iodoisophthalic acids, their salts and esters
and to methods for preparing same.
It is an object of this invention to provide derivatives of
isophthalic acid containing a plurality of iodine atoms and possessing
a relatively low toxicity as well as a substantial solubility in water
in the form of their salts. It is a further object 6f this invention
to provide for improved contrast media in X-ray diagnosis and to
further provide improved X-ray contrast agents which are relatively
stable under normal conditions of storage and use in the presence of
body fluids.
According to the present invention, it has been found that
aliphatic-acylated-5-aminopolyiodoisophthalic acids, specifically,
5acetylamino - 2,4,6 - triiodo-isophthalic acid, possess many valuable
properties. The compounds of the invention consist of the acids of the
general formula:
<img class="EMIRef" id="026598853-00010001" />
wherein R is H or lower acyl and n is 2 or 3, together with their
non-toxic salts and esters.
By ' lower acyl,' 'lower aliphatic ' and 'lower aLkyl ' in the
Idescription and claims we mean groups containing not more than 7
carbon atoms.
Some of the compounds of this invention
are of value as X-ray contrast agents in uro

graphy when visualization of the kidneys is
desired. Furthermore, under the proper tech
niques it it possible to obtain visualization of
the calyx and ureters. These panticular com
pounds which are utilized as urographic agents
when injected intravenously in the form of a
solution of one of their pharmacologically
acceptable salts, Isuch as the sodium salt, the
diethanolamine salt, glucamine salts and other
nonztoxic salts, are rapidly concentrated in the
kidneys and are excreted in the urine. In addi
tion, under the proper compression techniques
whereby the diffusion rate of the injected
compound throughout the blood stream is re-
duced, visualization of the calyx and ureters is
made possible within 5 to 20 minutes after in
jection. These aforementioned urographic
properties appear to be peculiar to those compounds of the general
formula which contain
three iodine atoms, a lower acyl group on the
amino-nitrogen atom and a free carboxylic
acid group preferably in the form of its salt.
For example, the formyl, acetyl and propionyl
derivatives of the biiodinated acids of the
general formula are excellent urograxphic
agents, with the acetyl compound exhibiting
the most desirable properties. As the number
of carbon atoms in the acyl group is increased,
there is an observable transitional change in
the properties of the compounds. Specifically,
the urographic utility decreases and the com
pounds become better suited as cholecysto-
graphic agents.
Esters of the acids of the general formula,
especially those compounds containing three
iodine atoms, provide for X-ray contrast agents
useful in bronchography and hysterosalpingo-
graphy. For these diagnostic methods the
esters are used preferably in oil solution or sus
pension. It is possible, however,- to employ
salts of the acids for use in bronchography and
hysterosalpiugography provided thickening
agents such as methyl- cellulose, gelatin, dex- tran, and other
acceptable agents are employed whereby proper concentration of the

radio- paque material is obtained with concomitant reduction in
diffusion rate away from the site under examination.
Thus it is seen that the compounds of this invention may be
administered parenterally, orally or deposited at the site to be
visualized.
Depending upon the mode of administration, the compounds therefore are
useful in urogenital, gynecological and gastrointestinal diagnoses.
The compounds of the invention possess a favorable therapeutic ratio
in that the dose: toxicity value is very small. It has been found that
the intravenous toxicity of many of the compounds of this invention
lie between 5 and 10 grams of substance per kilogram of body weight as
compared with a maximum of 400 mg. per kilogram as an effective dose.
Thus, these compounds can be utilized effectively as about
ane-twentieth of the LD/50 dose.
With 5-acetylamino - 2,4,6 - triiodo - isophthalic acid, as the
preferred compound in the form of a pharmacologically acceptable
soluble salt, excellent X-ray visualization is obtainable at a dose
which is corn parable to other diagnostic agents in use. At the dose
employed, there is a marked absence of side effects including venous
spasm which is sometimes noted with iodinated acids of this type.
Excretion urography is based upon parenteral administration, usually
by intravenous injection, of a contrast agent which is then excreted
bv the kidneys in such concentration that the kidneys and urinary
tract are clearly outlined in a roentgenogram. As stated heretofore, a
urogram may generally be taken within about five to twenty minutes
after injection.
It is generally known, however, that if normal renal function is
impaired, sufficient medium may not concentrate in the kidneys until
about one to nveny-four hours after injection.
With 5 - acetylamino - 2,4,6 ,triiodo-isophthalic acid in solution
as its sodium, or other therapeutically acceptable salt, generally
about twenty millilitres of a 50% solution is sufficient for
intravenous urography in adults. For children half the adult dose is
generally sufficient Obviously the restriction of fluid for several
hours prior to examination permits greater urinary concentration of
the salt allowing for more clearly defined roentgenograms.
It is not intended that the compounds of this invention be limited
solely to urographic, cholecystographic and similar media since the
properties of these compounds make them useful for many other
purposes. As heretofore stated, visualization of the gastrointestipal
tract is made possible by the proper administration of some of the
compounds of this invention. In such an indication the compounds may
for example be administered orally in the form of solutions,
suspensions, tablets, capsules and the like. It is not even essential

that soluble salts be employed. Furthermore, the utility of these
compounds is not recessarilv restricted to visualization of human
organs since they are equally adaptable for X-ray visualization of
other structures which cannot be visualized directly.
The compounds of this invention may be prepared from
5-amino-isophthalic acid according to the following scheme:
<img class="EMIRef" id="026598853-00020001" />
(The preparation of the requisite starting material
5-amino-isophthalic acid and its precursor Snitro-isophrhalic acid has
been reported in the literature). In addition to the above scheme,
amino-isophthalic acid in glacial acetic acid may be iodinated with
iodine monochloride in acetic acid giving rise to a mixture of both
monoiodo and diiodo-5-aminoisophthalic acid which are easily separable
by fractional recrystallization. It is possible to carry out the
reaction in such a manner so as to obtain a preponderance of the
diiodo acid over monohalogenated substances. By employing an excess of
iodine monochioride in hydrochloric acid it is possible to triiodinate
the amino-isophthalic acid although one can stepwise iodinate whereby
the intermediate monoor dihalogenated substance is isolated and
subjected to further iodination.
The jodinated amino acids are acylated with a suitable agent such as a
carboxylic acid, carboxylic acid chloride or anhydride preferably in
the presence of a trace of a strong mineral acid such as sulphuric
acid. Specific examples of acylated agents which are envisaged as
coming within the scope of this invention are formic acid, acetic
acid, acetyl chloride, acetic anhydride, prop ionic anhydride, butyric
anhydride and the like. Thus, although acetic anhydride is preferred
because of its relative economy and availability, other lower
aliphatic acylating agents may be employed.
The salts and esters of these compounds are prepared by the usual
methods employed in preparing salts and esters of organic acids.
The following examples further illustrate but in no way limit the
invention
EXAMPLE I.
Mono- and di-iodo-5-amino-isophthalic acid
To a solution of 26.4 g. of iodine monochloride and 40 ml. glacial
acetic acid is added a stirred suspension of 9 g. of 5-amino-iso-
phalioacid in 160 ml. of acetic acid over a onehour period. After
stirring for an additional hour, 200 ml. of water is added dropwise
and the mixture is allowed to stand at room temerature for about 30
minutes. The mixture is heated on a steam bath at about 70" for about
40 minutes and then allowed to stand at room temperature overnight
Excess iodine monochioride is destroyed bv the addition of sodium
bisulfite solution and the acetic acid is removed by steam

distillation. Upon the addition of concentrated hydrochloric acid to
the residue from the steam distillation there is obtained 10 g. of a
mixture of iodmated acids melting at 270-2850 (dec.). The crude
iodinated acid is recrystallized from 500 ml.
of water yielding mono-iodo - 5 - aminoisophthalic acid, m.n. 293
(dec.).
Upon the addition of concentrated hvdro- chloric acid to the
recrystallization liauor, there is obtained about 5 . of
diodo-5-amino- isonhthalic acid as a white microcrystalline solid,
m.p. 308309 (dec.).
EXAMPLE II.
Diiodo-5-amino-isophthalic acid
To a suspension of 9 g. of 5-amino-isophthalic acid in 1 liter of
water there is added sufficient concentrated hydrochloric acid (about
15 ml.) to effect complete solution, To the solution is then added
26.7 g. of iodine monochioride and the reaction mixture is stirred at
room temperature for three days. After removing a small amount of
insolubles by filtration, the filtrate is treated with sodium
hydrosulfite until the color indicative of excess iodine monochloride
disanpears. The solution is then saturated with sodium chloride and
extracted thoroughly with ether. The ether solution is dried with
anhvdrous sodium sulfate and evaporated to a residue, yielding 14 g.
of crude diiodo-5-amino-isophthalic add. The crude acid is purified by
recrystallization from water using decolorizing charcoal land
reprecinitated from the cooled filtrate by the addition of
concentrated hydrochloric acid.
EXAMPLE III.
2,4,6-Triiodo-5-amino-isophthalic acid
To a solution of 4.5 g. of 5-amino-isophthalic acid in 250 ml. of
water and 8.5 ml.
of concentrated hydrochloric acid there is added 14 g. of iodine
monochloride and the reaction mixture is allowed to stand for two
days. After filtration of the insoluble material, the filtrate is
treated with sodium hydrosulfite, saturated wtih sodium chloride iand
extracted thoroughly with ether. The ether extracts are dried over
anhydrous sodium sulfate and evaporated to a residue yielding 7.5 $ of
the crude acid of this example, m.p. 270274 . Purification is effected
by treating ia hot aqueous solution of the iodinated acid with
charcoal and reprecipitating the product from the cold filtrate by the
addition of concentrated hydrochloric acid, m.p. 278280 (dec.).
EXAMPLE IV.
Diiodo-5 -acetylamino-isophthalic acid
A suspension of 4.3 g. of diiodo-5-aminb isophthalic acid in 12 ml. of
acetic ainhydride is treated with 1-2 drops of concentrated sulfuric

acid and the mixture is refluxed for 30 minutes. After cooling, the
mixture is poured into 60 ml. of water, neutralized with .5-1 g. of
sodium acetate land evaporated to a residue iwz actt Recrystallization
from water and the addition of concentrated hydrochloric acid yields 3
g. of the acetylamino compound of this example, m.p. over 340
EXAMPLE V.
2,4,6 Triiodo-5-acetylamWino isophthalic acid
A suspension of 5 g. of 2,4,6-triiodo-5amino-isopht;halic acid in 15
ml. of acetic anhydride in the presence of 1-2 drops of sulphuric
acrid is refluxed for 30 minutes. The crude acetylated acid ils
obtained according to the procedure in the Preceding example.
Purification is effected by solution in dilute ammo- opium hydroxide
land treatment with decolorizing charcoal followed by filtration,
cooling and reprecipitation with concentrated hydrochloric acid.
Recrystallization from water as described in the preceding example
yields the lodinated acid of this example, 3 g., m.p. above 340 .
EXAMPLE VI.
2,4,6-Triiodo-5-formylamino-ibsophthalic lacid
To a mixture of 50 g. of 2,4,6-triiodo-5amino-isophthalic acid and 500
ml. of 8790;% formic acid is added about dx drops of concentrated
sulfuric acid and the resultant reaction mixture is heated and
'stirred on a steam bath for two hours. After cooling, the sulfuric
acid is neutralized by the addition of a small amount of sodium
acetate and the mixture is evaporated to a residue z zoo
Upon recrystallization of the residue from water to which has been
added concentrated hydrochloric acid, the formyl derivative of this
example is obtained.
EXAMPLE VII.
2,4,6-Triiodo5-propionylamino4sophthalic
acid
-A mixture of 25 g. of 2,4,6-triiodo-5-aminoisophthalic acid, 100 ml.
of propionic anhydride and 3-4 drops of concentrated sulfuric aciil is
stirred and heated at 125 to 1305 for approximately nvo hours. After
cooling, 500 ml. of water is added and the resultant mixture is-
stirred at room temperature until the excess propionic anhydride is
completely hydrolyzed. Upon concentration of the aqueous solution in
rra-IEo: there is obtained the crude propionylamino acid of this
example which is purified by recrystallization from water as
analogously described in Example III.
EXAMPLE VIII 2,4,6-Triiodo-5-butyrylamino-isophthalic acid A mixture
of 30 g. of 2,4,6-triiodo-5-amin- isophthalic acid, 100 ml. of butyric
anhydride and about six drops of concentrated sulfuric
acid is stirred and heated at 150 to 160 for about two hours. The
excess anhydrIde is destroyed by the addition of 600 ml. of water as

described in the preceding example and the sulfuric acid is
neutralized with sodium acetate. Upon evaporation of ithe resultant
mixture - in scato, there is obtained a semi-solid residue which is
dissolved in warm, dilute ammonium hydroxide. The alkaline solution is
treated with decolorizing charcoal and the butyrylamino acid is
reprecipitated by the addition of concentrated sulfuric acid and
recrystallized - from water as heretofore described.
EXAMPLE IX.
2,4,6-Triiodo-5-caproylamino-isophthalic acid
A mixture of 55.9 g. of 2,4-,6-triiodo-5- aminoXisophthalic acid, 500
ml. of anhydrous toluene and 20 grams of caproyl chloride is stirred
and refluxed for one hour. After cooling, the crude product is removed
by filtration and triturated with ether to remove unacylated material.
After decanting the ether layer, the remaining solid is recrystallized
from aqueous ethanol affording the caproylamino acid of this example.
EXAMPLE X.
Diethyl 2,4,6-Triiodo-5-acetylamino
isophthalate
To a mixture of 50 grams of 2,4,6-triiodo5-acetylamino-isophthalic
acid and 200 ml. of anhydrous ethanol is added 15 ml. of acetyl
chloride. The reaction mixture is allowed to stand at room temperature
overnight with occasional shaking whereupon it is diluted with one
litre of water and the precipitate so formed is removed by filtration
or decantation.
The crude ester is dissolved in ether and the ether solution is
washed, in turn, with sodium bicarbonate solution and water. After
drying the ether solution with anhydrous sodium sulfate, the solvent
is removed in eacuo. There is obtained the diethyl ester of this
example which is purified by recrystallization from aqueous alcohol.
Alternatively, the diethyl ester is prepared by treating a solution of
2,4,6 - triiodo - 5acetylamino-isophthalic acid in absolute ethanol
containing a catalytic amount of sodium ethoxide with diethyl sulfate
and isolating the ester in a known manner.
In addition to the foregoing procedures the diethyl ester of this
example is prepared by distilling an ethanol-benzene solution of the
amino acid in the presence of 0.5 g. of ptoluene sulfonic acid (or 0.5
ml. of concentraced sulfuric acid) and azeotropically removing the
water so formed.
EXAMPLE XI.
Disbdium sak of 2,4,6-triiedo-5-acetylamino-
isophthalic acid
A suspension of 5.58 grams of purified 2,4,6-triiodo-5-acetylamino
isopfrthalic and (obtained in Example V) in 15 ml. of distilled water
is neutralized with 30% aqueous sodium hydroxide until the pH rises

from 7 to 7.5.
The alkaline solution is filtered and the filtrate is evaporated in
vacua. Upon recrystallization of the residue from alcohol-ether, using
decolorizing charcoal, six grams of the sodium salt of this example is
obtained as a white crystalline solid.
It is generally not necessary to isolate the sodium salt per se~if the
appropriate quantities of amino acid, water, and alkali are used to
yield a solution containing the desired concentration of sodium salt.
EXAMPLE XII.
Di-N-methylglucamine salt of 2,4,6-triiodo-
5-acetylatnino isophthalic acid
To an intimate mixture of 4.67 grams of 2,4,6-triiodo - 5 -
acetylamino-isophthalic acid and 3.03 grams of N-methylglucamine is
added 4.0 ml.of distilled water and the mixture is stirred until
complete solutionis effected. - -
The solution is then diluted to 10 ml. with distilled water affording
a 77% W/V solution which is comparable in iodine content to a 50% W/V
solution of the sodium salt.
Alternatively the di-N-methylglucamine salt is isolated by evaporation
of the aqueous solution in vactro.
EXAMPLE XIII.
Di-diethanolamine salt of 2,4,6-triiodo-5
acetylamino isophthalic acid
One mole of 2,4,6-triiodo-5-acetylamino- isophthalic acid and -two
moles of diethanolamine are mixed and dissolved in water according to
the procedure described in
Example XII, giving rise to a similar W/Vconcentration
Isolation of the salt is accomplished by evaporation of its aqueous
solution in vacuo.
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* 5.8.23.4; 93p
* GB785671 (A)
Description: GB785671 (A) ? 1957-10-30

Ozone manufacture
A high quality text as facsimile in your desired language may be available
amongst the following family members:
FR1148901 (A) US2876188 (A)
FR1148901 (A) US2876188 (A) less
A A d, ' Date of Application and filing Complete Specification: March
19, 1956.
No 8490/56.
Application made in United States of America on March 21, 1955.
Complete Specification Published: Oct 30, 1957.
Index at acceptance:-Class 39 ( 1), I.
International Classification:-HO 5 f.
COMPLETE SPECIFICATION
Ozone Manufacture We, AIR REDUCTION COMPANY, INCORPORATED, a
corporation of the State of New York, United States of America, having
an office at 60, East 42nd Street, New York 17, New York, United
States of America, do hereby declare the invention, for which we pray
that a patent may be granted to us, and the method by which it is to
be performed, to be particularly described in and by the following
statement: -
This invention relates to the production of ozone from oxygen and more
particularly concerns the use of a glow-type electrical discharge in
such production.
It has long been known that ozone has many potentially important uses,
for example as a water purifying agent or as an oxidizer in chemical
reactions The fact that ozone has not been more extensively used is
due in large part to the unit cost of manufacturing ozone.

A basic factor in this cost is the low electrical power efficiences
which are obtained with known ozone manufacturing processes The heat
of formation of ozone is -34 4 kg cal.
per mole or 04 kw hours per mole, but all known ozonizers have
required five to twenty times this amount of energy to produce one
mole of ozone In addition to low efficiency, high concentration ozone
presents an additional problem in that power costs increase rapidly
with slight increases in ozone concentration For instance, it is
believed that conventional electrostatic ozonizers operate at an
efficiency not exceeding 10 per cent at an ozone concentration of one
weight per cent and not exceeding 4 per cent at an ozone concentration
of 6 weight per cent, and that electrolytic processes have not
exceeded 20 per cent efficiency at a maximum ozone concentration of 18
per cent by weight.
It is the primary object of the instant invention to provide an
improved method and apparatus for the production of ozone from oxygen.
Another object is to provide means for producing liquid ozone from
commercially-available oxygen.
L Ptice 3 s 6 d l A further object is to produce ozone at a much
higher electrical power efficiency than has been previously possible
50 The accomplishment of the above objects and others, along with
features and advantages of the invention, will be apparent from the
following description and the accompanying drawing in which: 55 Fig 1
is a flow sheet of the preferred form of the process of the invention
and Fig 2 shows one form of ozonizer constructed in accordance with
the invention and incorporating a U-tube which is immersed in 60 a
liquid nitrogen bath.
In its broad aspects, the present invention involves continually
introducing oxygen at subatmospheric pressure into a glow-type
electrical discharge ozonizer, converting oxygen to 65 ozone by such a
discharge, and condensing the ozone on very cold ozonizer surfaces
very rapidly after the ozone is formed The preferred operating
conditions are such as to provide an optimum electron density in
relation 70 to the molecular concentration of oxygen flowing through
or into the ozonizer, an optimum oxygen density or gaseous mean free
path and an optimum temperature In accordance with one form of
construction the ozonizer includes 75 a small-diameter U-tube which is
immersed in a quantity of liquid nitrogen The U-tube has electrodes at
the top of each leg and is constructed to permit the flow of a gas
therethrough and to provide for the suitable collec 80 tion of liquid
ozone.
Referring to the Fig 1 flow sheet, the oxygen supply 13 represents a
source of oxygen, such as -commercial oxygen cylinders This supply is
connected to an oxygen purification 85 device 15, such as a combustion

tube furnace which is originally packed with 12 gauge, pure copper
elements The flow path next includes a trap 17 containing liquid
oxygen for the removal of any carbon dioxide and water, 90 resulting
from the purification in device 15 A rotameter 19 is connected to trap
17 The ozonizer 21 which converts oxygen to ozone receives oxygen from
the rotameter 19 through 35.671 -i J 4 _ jc a valved conduit 23 The
outlet of the ozonizer 21 is connected to conduit 25 which extends to
a suitable valve 27 which is manipulated to provide communication with
the conduit 29 in the normal flow path or with conduit 31 which serves
for a purpose to be explained hereinafter Conduit 29 connects to a
trap 33 containing liquid nitrogen The remaining two items in the flow
path are a vacuum pump 35 and a meter 37 for measuring the effluent
gas from the ozonizer A conduit 39 is connected to the outlet of meter
37 and serves to pass the effluent gas from the ozonizer to suitable
oxygen recovery means (not shown) or other devices.
The flow sheet also shows the means for determining the pressure in
the ozonizer 21.
This means includes conduit 41 having valve 43, a combustion tube
furnace 45 and a pressure measuring device 47 which is connected to
the furnace 45 by means of conduit 48.
In Fig 2 the details of the ozonizer 21, which includes a U-tube, are
shown The conduit 23 (leading from the rotameter 19 shown in Fig 1) is
connected to the inlet tubing 51 of the ozonizer This tubing 51
branches at 53 and then joints tvo dip loops 55, 57 which connect to
the U-tube 59 at locations just below the electrodes 61, 63 in the
tops of each leg 65, 67 of the U-tube The dip loops 55, 57 serve to
move the incoming oxygen into a cooling indirect heat exchange with
the liquid nitrogen in container 69, which is represented by dashed
lines and also serve to prevent electrical short circuit of the
ozonizer which would occur if the oxygen inlets were joined to a short
uncooled common oxygen source Any suitably insulated container, such
as a Dewar flask, can be used for the liquid nitrogen.
The electrodes 61, 63 are made from a commercially available, high
purity aluminium.
The annular space between the side of the electrodes and the interior
surfaces of the adjacent portions of the legs 65, 67 is about 0 001 of
an inch in width The electrodes are supplied with electricity, by
tungsten leads 71, 73, from a neon-sign type of transformer (not
shown) which is operated by 110 volt A C.
supply Above the electrodes, two bleed-offs 75, 77, which provide for
removal of heat from the electrodes, are connected to the upper part
of the legs of the U-tube and extend to the conduit 25 leading to the
vacuum pump above mentioned An effluent gas conduit 81 extends from
the bottom 87 of the U-tube to the conduit 25 and also connected to

the bottom of the U-tube is a drain or exit conduit 83 which empties
in a bulb 85 A pressure tap conduit 89 is connected to the U-tube near
its junction with the effluent gas conduit 81 and extends to, and
makes connection with, conduit 41 shown in Fig 1.
The bleed-offs 75, 77 have an inside diameter of 0 5 millimeters The
inside diameter of tube 25 is 30 millimeters The inside diameter of
the U-tube legs 65, 67 the effluent gas conduit 81, and the tube 83
leading to bulb 85 from the bottom of the U-tube arc, respectively, 9
millimeters, 8 millimeters, and 6 millimeters The inside diameter of
the pres 70 sure tap tube 89, which connects with conduit 41 shown in
Fig 1, is 5 millimeters The interelectrode distance is about 19
inches.
In operation, commercial-grade cylinder oxygen ( 99 6 per cent pure)
containing as im 75 purities, principally argon with some nitrogen,
from supply 13 is passed through the furnace which is operated at 1450
'F In the furnace, any trace of combustible hydrocarbon contaminants
which may be in the oxygen are 80 burned to water and carbon dioxide
The small amounts of water and carbon dioxide present in the oxygen
are removed in the liquid oxygen trap 17 in which they solidify The
purified gaseous oxygen is admitted, at a controlled 85 rate by the
valve in conduit 23, to the previously evacuated ozonizer through the
calibrated rotameter 19 A glow-type discharged is then initiated in
the ozonizer 21 between the electrodes 61, 63 The ozonizer has been
previ 90 ously cooled with liquid nitrogen The refrigerant level is
maintained at a level one-quarter inch below the bottom level of the
electrodes during the entire run Liquid ozone immediately condenses on
the walls of the U-tube and 95 drains into the bulb or reservoir 85
The effluent gas, including the 0 4 per cent of other components, from
the ozonizer flows through outlet 81 and conduit 25 to the downstream
trap device 33 which is comprised of two 100 traps filled with glass
wool and refrigerated at a temperature of 1960 C by liquid nitrogen.
This effluent then passes through the vacuum pump 35 and the meter
means 37 which is a wet gas meter From meter 37 the residual 105
effluent is passed through conduit 39 to recovery means (not shown) or
otherwise disposed of.
For determining the pressure adjacent the outlet of the ozonizer the
gas is passed through 110 pressure tap 89, conduit 41, and valve or
stopcock 43 to the combustion tube furnace 45 (shown in Fig 1) which
is packed with pure copper wire and is operated at 1200 'F This
furnace is installed as a safety device, serving 115 the dual purpose
of preventing contamination of the system by the pressure measuring
device 47 and of preventing small amounts of ozone from reaching the
sensing element of the pressure gauge The pressure gauge which is pre
120 ferred is a commercial item which operates due to the ionization

of gas molecules by a radioactive source and the resulting ion current
which is directly proportional to the number of ions collected in a
given time The pressure of 125 synthetic rubber (Neoprene) in the
sensing element of the pressure gauge necessitated the use of the
furnace 45.
The furnace 45 is typical of safety measures incorporated in the
entire system Extreme pre 130 785,671 through the oxygen is derived
from a currentlimiting type of transformer which is operated from an
alternating current supply, for example a conventional 60 cycle, 110
volt supply.
With the illustrated ozonizer in which the oxygen flows down each leg
of the U-tube, it should be noted that the electrical discharge is
used to full advantage since the more potent, ozone-producing part of
the discharge alternates between electrodes in accordance with the
alternating current Electrical measurements were made by a circuit
which included a voltage divider and voltmeter for measuring the
average secondary volts of a 10,000 volt neon sign transformer which
is an un-enclosed core and coil type immersed in mineral oil.
Peak voltages were measured by means of an electrostatic voltmeter The
secondary current was measured by a milliameter and the secondary watt
value was obtained by multiplying secondary current by the average
secondary volts and using a power factor equal to unity.
Per cent power efficiency was calculated as follows:
cautions must be taken to prevent even a trace of combustible
hydrocarbons from contaminating the ozone, since such contamination
might cause detonation of the ozone.
During operation, it is apparent that a very small flow of oxygen will
move up past the electrodes 61, 63 and out of the U-tube through bleed
offs 75, 77 which are of such construction (diameter and length) as to
prevent electrical discharge therethrough between electrodes This
small flow of oxygen past the electrodes, thus serves to remove heat
It is to be noted that the electrodes are removed from the region
where they could affect the ozone draining down the walls of the
discharge vessel and that the maximum average distance for an ozone
molecule to travel in order to contact a very cold surface is of the
order of 4.5 mm A very important related feature is the very low
temperature of the U-tube walls which is provided by the liquid
nitrogen bath at -196 C This is significant because it serves to cause
the removal of the ozone from the reaction and also it prevents
decomposition of ozone by electrons It is noteworthy that at the
boiling point temperature of liquid air (about 1910 C) the vapor
pressure of ozone has been determined to be about 0 015 mm Hg while at
the boiling point temperature of liquid nitrogen ( 1960 C), the
corresponding vapor pressure is about 0 0035 mm Hg With prevailing

operating pressures, this factor is, of course, even more significant
It is considered essential for satisfactory operation that the
refrigerant bath be below 193 C and preferably at 1960 C.
Since gaseous ozone is usually desired for commercial uses, the
collected liquid ozone can be slowly evaporated by lowering, with
suitable conventional means, the liquid nitrogen bath after the
ozonizer's oxygen and electrical supplied are discontinued In this
manner, the liquid ozone is slowly evaporated and escapes in gaseous
state via valved conduit 31 for use in chemical reactions or other
operations It is also possible to obtain the liquid ozone as such from
the ozonizer by means of suitable conduits, valves, couplings, and
containers, which can be connected to the ozone drain tube and would
be suitably arranged with respect to the nitrogen container The
transfer apparatus must be such that explosive impurities, such as
hydrocarbons, do not contaminate the ozone With this arrangement, it
is possible to continuously remove liquid ozone.
The electricity for effecting the discharge Per cent Power
Efficiency0.835 x ozone production rate (g/hr) x 100 secondary watts
The value of 0 835 watts has been determined as the theoretical energy
necessary to form one gram of ozone, based on 100 per cent conversion
of electrical energy for supplying the 34 4 K cal per mole for ozone
formation.
The production rate was calculated by assuming the difference between
oxygen in and oxygen out to be ozone The ozone condensed per unit time
in other similar tests was measured by the liquid level rise in a
calibrated tip or bulb at the bottom of the U-tube and it was
established that the measured quantity in the present process was
entirely ozone and was equivalent to the difference between the input
and output of oxygen, as converted to ozone Gas conversion was
calculated in the following manner:
2 in- 2 out x 100 =per cent gas conversion 02 in Data and results,
based on the above calculation and obtained during the operation of
the disclosed ozonization system shown in Fig.
1 and 2, are presented in the following table: 105 785,671 TABLE I
Sec.
Run Pri Volts No Volts Average Sec.
Volts ESVM Sec I 2 Flow % % Gas (ma) (cc/min) P E Conv.
03 Sec.
Pressure Production Volt (mm Hg) (gm/hr) Amps 1 30 2 30 3 30 4 35 37 6
39 5 7 39 5 8 40 9 40 42 11 45 12 45 13 45 14 45 45 16 45 17 45 18 48
19 50 50 21 50 22 50 23 50 24 50 885 829 985 1075 1010 1210 1210 1165
1175 1310 1165 1265 1110 1175 929 1300 1290 1545 1120 1558 1531 1531
1120 1540 1980 1830 2080 2320 2310 2500 2550 2490 2490 2680 2460 2640
2340 2450 2050 2630 2630 3050 2400 3040 3030 3050 2390 3050 2.9 3.3

2.4 3.3 3.8 3.9 3.9 4.1 4.1 4.3 5.9 5.5 6.4 6.1 7.05 5.6 5.3 4.6 7.5
5.3 5.3 5.3 7.3 5.3 23.5 13.8 2.6 48.5 53.5 68.5 68.5 68.5 68.5 83.5
83.5 93.5 73.5 83.5 33.5 2.0 93.5 123 5 83.5 138 5 133 5 133 5 83.5 5
37.4 22.95 7.8 50.5 47.4 52 52.3 53.1 50.4 48.5 48.6 46.9 44.8 46.4
27.1 1.96 48.4 48.9 45.2 49.6 50.2 51.9 43.7 49.7 59.7 64.8 52.8 52.2
50.2 50.4 52.8 49.7 45.8 57.2 50.0 61.7 56.8 75.3 50.6 39.3 63.6 42.1
42.6 45.1 61.2 41.7 0.23 0.125 0.054 395 53 58 67 59 655 49 58 19 058
67 97 535 984 935 88 515 1.18 0.752 0.223 2.15 2.39 2.94 2.96 3.04
2.91 3.28 4.01 3.92 3.81 3.98 2.12 1.171 3.97 4.16 4.55 4.9 4.88 5.06
4.29 4.85 2.56 2.735 2.36 3.55 4.21 4.72 4.72 4.78 7.82 5.64 6.88 6.96
7.1 7.17 6.55 7.28 6.84 7.1 8.4 8.25 8.13 8.13 8.16 8.15 586 302 not
measurable 1.4 1.54 2.05 2.04 1.98 2.07 2.71 2.2 2.86 1.74 2.22 514
not measurable 2.83 4.5 38 4.88 4.59 4.47 1.99 4.74 02 Volume Out
(liters/hr) 00 mthis form of the apparatus, it is to be noted that the
oxygen is introduced at the midpoint between electrodes and then is
subjected to electrical discharge as it flows up each leg, rather than
down each leg as is illustrated 70 The residual gases are caused to
move past the electrodes and out of the U-tube through conduits by
means of a vacuum pump With this mode of operation, the residual gases
tend to remove heat from the electrodes The level 75 of the liquid
nitrogen bath was as previously described, as were all operating
conditions and characteristics It is also feasible to make ozone, in
accordance with features of the present invention, by using a U-tube
in which 80 the oxygen is admitted at the top of one leg and a vacuum
pump is connected to the top of the other leg, but efficiences will be
somewhat lower.
With reference to the ozonizers herein dis 85 closed, it is to be
noted that the oxygen flowthrough in the ozonizers prevents the
accumulation of gases, such as argon and nitrogen, which will not be
condensed under the operating conditions and so interference with the
90 electrical discharge does not occur The residual gases, after ozone
formation, are removed by the flow means such as conduit 81.
It can be stated that another material which has been found suitable
for the electrodes is 95 stainless steel.
It is to be noted that it is essential that the oxygen be purified by
means such as the copper oxide furnace 15 and that the entire system
does not contain any source of oxidiz 100 able materials Thus, there
is nothing in the oxygen, admitted to the ozonizer, which will trigger
the decomposition of ozone and there is nothing in the system, such as
rubber gaskets, which can contaminate the ozone 105 It is also to be
noted that the geometry of the U-tube is such that the ozone drains
away from the electrodes.
In all ozonizers which were satisfactorily tested, it was apparent
that for maximum 110 efficiency the ozone must have an adequate

condensing surface and must be refrigerated to at least 1930 C and
preferably 1960 C.
In most cases, the walls of the U-tube were refrigerated by liquid
nitrogen at 1960 C so 115 that the ozone would be condensed rapidly
after formation The subatmospheric pressure in the ozonizers is of the
order of less than 1 millimeter Hg absolute.
The space defined by the electrodes and the 120 condensing surface is
referred to as a conversion zone.
The term "glow-type discharge," as used herein, means the type of
electrical discharge or flow of current in a gas which occurs in 125 a
neon sign or a fluorescent lamp Glow discharges take place at low
pressures (a few mm of mercury), as is briefly described in the texts,
such as Sears' " Principles of Physics " ( 1947).
Of course, it is to be appreciated that, due to 130 Other tests were
made with the primary volts varying between 52 and 60 volts In
general, somewhat higher average secondary currents, oxygen flows, and
pressures resulted.
Because of the voltage-current relationships of the discharge tube, it
is necessary to use the above-mentioned current-limiting type
transformer The secondary voltage output of this type of transformer
is regulated in an inverse relation to its current capacity If the
primary input of such a transformer is set at different voltages as
shown in the above table, a series of curves may be plotted from the
secondary electrical characteristics at various pressures in the
discharge tube By reference to runs numbered 19 to 24 in the above
table, it can be seen that the data, or a curve thereof, shows that
the power efficiency rises to a maximum as pressure increases and then
decreases somewhat with a further increase in pressure The point at
which the secondary current is at a minimum at high pressure is called
the " break off" point because the discharge cannot be maintained
beyond this point It has been determined, as by runs 19 and 24, that
the highest electrical efficiencies occur adjacent this " break-off "
point It is apparent that this characteristic is a function of
electron density, i e, ma/unit number of gas molecules Thus, it was
determined that, with below atmospheric pressure which is adjusted in
relation to the amount of current to give an electron density of
between 6.0 and 8 5 milliamperes per millimeter mercury of pressure,
very high electrical efficiencies are obtained Runs numbered 4, 5, 7,
10, 17, and 22 are runs which were made quite adjacent the " break-off
" point and it is apparent the quotients of the given secondary
milliamperes divided by the given pressures (in mm Hg) for these runs
are within the range of 6 0 to 8 5.
From the above data, it is also apparent that the best power
efficiencies are obtained when between a 40 to 60 per cent gas

conversion occurs.
From various tests, it was determined that the inside diameters of the
U-tubes must be within the range of 5 to 12 millimeters or, stated
differently, the opposed refrigerated wall segments of the conversion
zone or chamber must be spaced between 5 and 12 millimeters apart In a
flattened U-tube, such as was tested, it is apparent that most of the
opposed wall segments would be closely spaced, in the range above
mentioned This spacing feature, together with the low temperature
provide for the rapid condensation of the ozone.
In another design of an ozonizer which worked satisfactorily, the
oxygen is fed to the bottom of the U-tube and then divides and flows
up each leg of the U-tube The residual gas is removed from the top of
each leg by conduits which are connected to the top of the U-tube
legs, above the electrodes With 785,671 the conversion of oxygen to
ozone, the ozonizers of the present invention differ from the neon
sign discharge devices.
As above suggested, it is to be understood that the elements of the
entire flow path are so selected and constructed that there is
substantially no possibility of oxidizable substances entering the
system and reacting with the ozone Thus, the part of the system which
may contaminate the ozone is maintained absolutely free of hydrocarbon
substances which will react with ozone If it is found necessary to
provide a seal, inert lubricants are used.
It is to be noted that the positive column of the electrical discharge
which produces most of the ozone alternates with the alternating
current and hence ozone is made in equal amounts in each leg when
split-feeding is used.
Very important features of the above glowtype discharge process are
the use of low temperature refrigeration and the wall spacing whereby
it is possible to condense the ozone immediately after it is formed
and hence the ozone-to-oxygen decomposition is prevented.
From the foregoing, it is apparent that it has been discovered that
the maximum electrical efficiency occurs adjacent the "breakoff"
point, that is, the point at which the secondary current is at a
minimum at relatively high pressure The discharge cannot be maintained
beyond this point In the low pressure, low temperature glow-type
discharge ozonizer of the invention, the " break-off " feature defines
in practical terms the preferred operational condition which is
involved in the highly complicated conversion of oxygen to ozone Thus,
there are definite advantages in maintaining the quotient of the
current in milliamperes divided by the unit number of oxygen molecules
as indicated by the measurement of pressure in millimeters of mercury
in the range of 6 5 to 8.
From the above description, it is also apparent that means have been

provided for effecting the steps of, removing any nonoxygen
components, such as argon and nitrogen, from the ozonization zone so
that an effect on the electrical discharge will not result due to the
concentration of argon, for instance, with the result that
commercial-grade, highpurity oxygen as obtained by liquefaction and
separation can be used Also means have been provided for cooling the
oxygen to be introduced, as shown in the illustrated ozonizer.
It is to be understood that this invention is not limited to the
specific illustrative embodiment herein disclosed but includes such
modifications as fall within the scope of the appended claims.
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* 5.8.23.4; 93p
* GB785672 (A)
Description: GB785672 (A) ? 1957-10-30
Monoazo dyestuffs of the 2-hydroxy-3-naphthoic acid arylamide series
t
785,672 42 Date of Application and filing Complete Specification:
March 28, 1956.

g E No 9739156.
Application mode in Germany on March 30, 1955.
Complete Specification Published: Ocr 30, 1957.
Index at acceptance:-Class 2 ( 4), P 1 A 2 B 2 A, P 9 A 4 (B: C).
International Classification:-C 09 b.
CO 1 PLETE SPECIFICATION
Monoazo Dyestuffs of the 2-Hydroxy-3-Naphthoic Acid Arylamide Series
SPECIFICATION NO 785,672
The inventor of this invention in the sense of being the actual
deviser thereof within the meaning of Section 16 of the Patents Act,
1949, Is Hans Raab, of Friedrich-Bayer-Strasse 10,
Leverkasen-Bayerwerk, Germany, of German nationality.
THE PATENT OFFICE, 2 oth November, 1957 CO.NH CONH 2 wherein R is an
alkyl radical.
The new azo dyestuffs are obtainable by coupling a diazotized
3-amino-4-alkoxy-1benzoyl-urea with 1-(
21,31-hvdroxvnaphthoylamnino)-2,4-dimethoxy-5-chlorobenzene The
dyestuffs are especially suitable as red pigment dyes for dyeing and
printing fibres, lacquers, resins and other materials The dyeings
obtained thereby are distinguished by their good fastness to light, an
excellent fastness to solvents and high brilliancy of shade.
The following Example is given for the purpose of illustrating the
invention: EXAMPLE.
15.2 Parts by weight of 3-amino-4-methoxy1-benzoyl-urea are stirred in
200 parts by volume of water and 30 parts by volume of hydrochloric
acid ( 195 Be) and then diazotized, after an addition of 30 parts by
weight of ice, with 16 7 parts by volume of 30 % sodium nitrite
solution The diazo salt solution is filtered with the addition of
active carbon.
28.8 Parts by weight of 1-( 21,31-hydroxylPrice 3 S 4 46 DB 00816/1 (
6)13605 100 11157 R weight of a red pigment dye of good fastness to
light and excellent fastness to solvents are 55 obtained.
A dyestuff of similar properties is obtained if, instead of 15 2 parts
by weight of 3-amino4-methoxy-1-benzoyl-urea, 16 2 parts by weight of
3-amino-4-ethoxy-1-benzoyl-urea are 60 used.
The diazo components used in this Example are obtainable by treating a
3-nitro-4-alkoxy1-benzoyl-chloride with urea and reducing the nitro
group in the acylated ureas thus obtained 65 The
3-Amino-4-methoxy-1-benzoyl-urea has a melting point of 308 C, and the
3-amino-4ethoxy-1-benzoyl-urea has a melting point of 3200 C.
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