11 Carbon-dioxide - CO2 - R744 - (Carbonic Acid) The History of an Interesting Substance // Kohlendioxid – CO 2 – R 744: Zur Geschichte eines interessanten Stoffes

eurammon promotes all natural refrigerants which support the use of the refrigerant
ammonia. Due to the problems with ODP and GWP, these substances have again become a
focal point of scientists, users and politicians. Apart from ammonia, water, hydrocarbons–e.g.
propane–and carbon dioxide belong to these natural refrigerants. The latter with the ISO
code R 744 and the chemical formula CO2 has in recent years witnessed a revival in
research but also even as a refrigerant and a secondary refrigerant in real applications.
This eurammon information offers a view into the history of carbon dioxide, for which from
now on the term CO2 will be used.

We are surrounded by CO2 in the atmosphere since primeval times, even though today in a
lower concentration in comparison to nitrogen (N2) and oxygen (O2), but possibly with great
impact on this atmosphere. The atmospheric CO2 is released from very different deposits
and processes, such as volcanoes, oceans (as storage), carbonic acid from natural springs,
combustion of fossil fuels, forest fires, exhaust fumes from chemical production and
processing of natural gas and crude oil and fermentation processes. Even human beings and
animals emit CO2 with their exhaled air, a human being e.g. about 1 kg per day varying due
to constitution and workload. The fermentation process in the beer production results up to
3.5 kg CO2 per hectolitre beer.

Under the trade name “carbonic acid” we encounter CO2 in many non-alcoholic beverages
and in other fields, e.g. drinking-water purification, wastewater treatment, fire-extinguishing
technology, high-pressure extraction, pest control, food refrigeration, in deep-freezing and
cold-milling, as inert gas and dry ice, in medical applications and again these days as
refrigerant and secondary refrigerant in refrigeration systems. These versatile industrial
applications result from the special properties of CO2. As a gas, carbon dioxide is neutral, to
name only some of the properties, in colour, smell, taste, and has a high density (standard
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state about 2 kg/m³), roughly 1.5 times the density of air. On top of that, the chemical
compound CO2 is very stable.

The critical point is at +31.0°C and 73.83 bar
the triple point is at -56.6°C and 5.18 bar
the sublimation point is at -78.9°C and 0.981 bar

Often the name “carbonic acid” is used–not quite correctly–as a synonym for CO2 (carbon
dioxide). Only in a compound with water CO2 becomes carbonic acid (H2CO3).
The CO2 content in our atmosphere has risen from 280 ppm in 1800 via 295 ppm in 1900 to
368 ppm in 2000, which the majority of scientists blame on anthropogenic influences. The
carbon/carbon dioxide cycle and the CO2 equilibrium in nature and the greenhouse effect
shall not be further discussed in this eurammon information. Below some highlights of the
”history” of CO2 shall be discussed without claiming to give a complete overview.
CO2 has from time immemorial been known to emerge from geological sources. The Romans
already knew the agreeable effect of bathes containing CO2 from volcanic sources on the
blood circulation. The hazardous effect (suffocation due to air displacement) was also known
to them. Plinius calls it ”spiritus letalis”, the "lethal spirit", which kills its victims without leaving any traces. It used to be the custom to place candles in fermentation cellars to monitor the ambient air, their extinction indicating an excessive concentration of CO2.
For centuries CO2 has been known as a waste gas from fermentation and lime works.


An older method to produce carbon dioxide was to pour water on marble pieces or limestones
with hydrochloric acid or sulphuric acid, thus forming CO2 gas. Paracelsus (1493–1541)
already made a clear distinction between CO2 and air and J. B. van Helmont (1577–1644)
realized that the gases produced in different ways were in fact the same substance, which
was a bit later also found as a component of air.

The French physicist Lavoisier (1780) coined the word "acide-carbonique" (translating into
carbonic acid) after he had detected the composition of the gas of one part carbon and two
parts oxygen. In 1823 the physicist Faraday (1791–1867) was the first who managed to produce liquid CO2 in small laboratory quantities. CO2 in solid form as snow was first produced by Thilorier in

1834 by expansion of liquid CO2 to atmospheric pressure. He reported "that the snow could
be compressed easily, had a temperature of -78.5°C at atmospheric pressure and without
melting first, transiting immediately from the solid into the vaporous state” (sublimation). This
solid CO2 is called ”dry ice”. Dry ice was first produced industrially in Montreal in 1924. After
the Dry Ice Corporation New York propagated dry ice for the transport of ice cream and
frozen food, the annual consumption in the USA rose from 135 t in 1925 to 120,000 to in
1935. A considerable dry ice production in Germany started at the beginning of the 1930s.
The ”Taschenbuch für Kälte-Techniker” (pocketbook for refrigeration mechanics) (1939) by
W. Pohlmann mentions a production of 5,500 t in 1938 and 15 manufacturers. In the cities
the price was about 0.30 to 0.40 reichsmark per kg. In the same reference, 75% of the worldwide production were attributed to the USA, which produced 150,000 t in 1937.
Even today dry ice is used in considerable quantities, chiefly for transportation refrigeration of
food. The total European dry ice production was about 120,000 t in 2000. Liquid CO2 was
and is produced and used or consumed in even larger quantities. In Germany it was Dr. phil
Wilhelm Carl Raydt a teacher at a grammar school for sciences in Hannover who started the
liquefaction and industrial application of CO2 (1877). He liquefied CO2 via a reciprocating
compressor at ambient temperature by hydrocooling. One of his first applications of CO2 was
the lifting and relocating of a 5 t anchor stone in the port of Kiel commissioned by the imperial navy. For this task Raydt had a diver fasten a rubber balloon on the anchor stone and had the balloon filled with CO2 from a steel bottle.

Thus the anchor stone could be floated to another place.
In 1880 Raydt took out a patent on "A Procedure and Apparatuses to Impregnate, Lift and
Cast Water Aided by Droppable Carbonic Acid". This is the basis for the production of
carbonated beverages and the use of CO2 in the draught beer dispensation to pressurize and
eurammon-Information No. 11 / Updated version, May 2011
transport the beer to the tap. This Dr. Raydt is mentioned, though with a different spelling, in
the ”Lebenserinnerungen” (memoirs) (1914) of Heinrich Dräger (founder of the Dräger-
Werke, Lübeck). There he writes about a newspaper article, which he read a year ago or
”It dealt with liquid carbonic acid and how it could be used in commercial applications. The
inventor Dr. Rhaidt intended to fill it into bottles and use it for beer dispensation. That is why
he cooperated with a company in Hanover and their apparatuses would soon be on the
market. The omniscient journalist had then used this news to criticize this intention very
scholarly and disparagingly. Liquid carbonic acid had the incredible pressure of 35
atmospheres, which even increased significantly in warm temperatures. No landlord would
accept such a bomb in his house and, by the way, the police would never give their
permission for this. The railroad companies would hardly want to transport such explosives
as furthermore there were no kegs which could withstand such a pressure. To confirm his
analysis he had added a mathematic formula so that even the most simple-minded reader
had to understand this man was right.”

Heinrich Dräger realized that liquid carbonic acid was the ideal pressurizing agent for beer.
He developed the then available beer pressurizing apparatuses (CO2 pressure reducers) for
the draught beer dispensation to perfection. Starting in 1902/03 H. Dräger, his son Bernhard
and the Lübeck surgeon Dr. Otto Roth developed the first mechanical narcotic apparatus on
the basis of this very beer pressurizing apparatus in order to achieve a controlled mixture of
air or oxygen and the inhalation narcotic (award at the world exposition in St. Louis in 1904).
A license agreement between Dr. Raydt and the Chemische Fabrik Kuhnheim & Co., Berlin-
Niederschöneweide, in 1882 was the basis to start the first industrial production of liquid CO2
in Germany there.
In 1883 it was transferred into the company "Actien-Gesellschaft für Kohlensäure-Industrie"
(since 1931 Agefko), which in its first financial year (1884) produced 122,088 kg CO2. Its first
general manager, Hugo Baum, had a rather unconventional way to advertise his liquid CO2
by asking the imperial shipyard in 1884 to be allowed ”to supply the officers’ mess hall on
one of His Majesty’s ships with two bottles of liquid carbonic acid free-of-charge as well as
one complete beer pressure apparatus on loan”. The ”bottles” had a gross weight of about 60
kg, see below.

In 1886 the company Rommenhöller & Co., Rotterdam, managed to thwart the Raydt patents
making room for further manufacturers. Six of these companies in competition to Agefko
merged to a sales group (syndicate?) the "Kohlensäure-Verkaufs-Verein Ges. mbH" in 1892,
which was joined by nine further companies. From October 1, 1895, to September 1, 1896,
this group sold 8.5 million kg CO2. Due to internal problems, further external competition and
price wars it disintegrated as early as September 1, 1899 (status: 20 companies). But on
January 1, 1901, a new union was founded in Berlin, the "Deutsche Kohlensäure-
Gesellschaft mbH" (DGK). Except for the Buse company, all the meanwhile existing 30
carbonic acid factories – Agefko as well – joined the union.

The gas industry and the use of its liquefied gases received great impulses by the invention
of light and safe compressed-gas bottles. In 1886 Howard Lane and Richard Taunton took
out the English patent No. 12371 on the manufacture of weldless steel bottles made of
oneinch-thick flat steel plates by forging, drawing, pushing, and pressing.
In the same year, the brothers Max and Reinhard Mannesmann in Germany presented their
cold-rolling process for the manufacture of weldless pipes, which was soon introduced into
the manufacture of thin-walled compressed-gas bottles. Before, an empty steel bottle forged
out of one block weighed about 52 kg for a charge of 8 kg CO2. Today an empty
compressed-gas bottle for a content of 10 kg made of steel weighs about 16.5 kg and made
of aluminium about 12 kg.

As a refrigerant, CO2 was first proposed by Alexander Twinning in his British patent of 1850.
In America Thaddeus S. C. Lowe experimented with CO2 for military balloons in the 1860s
and made the discovery to use CO2 as a refrigerant. Lowe started to develop refrigeration
systems and in 1867 took out the British patent No. 952. Around 1869 he erected a CO2
machine in Jackson, Miss., and built another one on board a ship for the transportation of
frozen meat from Texas to New York.

The first CO2 compression refrigeration system in Europe was built by C. Linde in 1881
(Plank) (according to Göttsche in 1883), manufactured by the Maschinenfabrik in Augsburg
and put into operation at Krupp in Essen in 1882. Linde was, however, not an advocate of
the CO2 machine and supplied it only on explicit request. He favoured ammonia. From 1893
to 1894 Linde tested such a CO2 machine in Munich in order to prove the inferiority of the
CO2 machines of his competitors Riedinger and Hall. He also wanted to prove that CO2
machines could not reach the efficiency of NH3 machines.

Since 1881 the above-mentioned W. Raydt in Hanover had also worked on the construction
of CO2 machines. In 1884 he took out the British patent 15475 for a "compression ice-making system using carbon dioxide".
An essential contribution to the breakthrough of CO2 machines was the work of Franz
Windhausen in Berlin (1886). The first CO2 ship refrigeration systems in Germany were built
according to his patent DRP 37214 by the companies Riedinger in Augsburg and Haubold in
Chemnitz. In 1886 Windhausen took out the British patent 2864 for his CO2 compressor. In
accordance with this patent the company J. & E. Hall in England started to build ship
refrigeration machines. The first was installed in the steamer “Highland Chief” in 1890 for the
transportation of frozen meat.

At the same time, in 1887/90, the development and manufacture of CO2 machines and
plants in the USA started. The company "Kroeschell Bros. Ice Machine Company"
propagated CO2 as a "safety refrigerant" in contrast to sulphurous acid and ammonia, which
were termed extremely "harmful". Kroeschell manufactured CO2 refrigeration machines
according to a patent (1898) by the Hungarian Julius Sedlacek and called his compressor
series "North Pole compressors". In 1924 Kroeschell merged with the Brunswick
Refrigeration Company of New Brunswick, N.J., which manufactured ammonia compressors.
Further U.S. companies, occupying themselves with CO2 compressors and systems were
among others a company founded in 1915 in Chicago by Fred Wittenmeier (former employee
of Kroeschell’s), the Carbondale Machine Company and the American Carbonic Machinery
Company. The hitherto used cold air and ammonia machines in ships were more and more
replaced by CO2 machines. Ashore it was chiefly air-conditioning systems and the food
industry, which were equipped with CO2 refrigeration systems.
According to Bäckström 60% of the ship refrigeration plants and 10% of the land refrigeration
plants were still operated with CO2 in 1950. Göttsche (1912/15) names 29 factories in Europe building CO2 refrigeration systems, 23 of them in Germany. Small refrigeration machines had a performance of between 2,300 and 16,000 kcal/h, (e.g. by the company Riedinger).

Conventional series had a capacity range of 2,000 to 140,000 kcal/h at a brine cooling from -
2°C to -5°C. So-called plunger condensers or spray condensers served as liquefiers.
As a peculiarity Göttsche mentions a manual CO2 ice-making machine, type "Kolibri" by Ths.
Sabroe & Co. in Aarhus. The compressor was started via a manual crank. The machine
could produce 1.5 to 2 kg ice per hour. According to Göttsche/Heinel almost 3,000 ammonia,
1,600 carbonic acid and 800 sulphurous acid machines were in use in Germany in 1908. 600
kg a year were regarded as a normal refrigerant loss due to leakages according to Pohlmann
(1935), e.g. in a CO2 brine system with a capacity of 80,000 kcal/h and a charge of 420 kg
CO2. The price for CO2 was 0.75 RM (reichsmark)/kg (syndicate price) and 1.29 RM/kg in the
small retail trade.

The development of CO2 refrigeration systems in Europe was similar to that in the USA. CO2
was used successfully in marine and industrial refrigeration systems in the early 1890s and
for air-conditioning purposes since about 1900 to a peak in the mid-1920s in the USA. Due to their nontoxicity and nonflammability, CO2 refrigeration systems were used in food markets, kitchens, hospitals, hotels, restaurants, theatres, passenger ships etc. Predominantly indirect refrigeration systems with a calcium chloride brine were used.

With the beginning of the 1930s, CO2 in industrial refrigeration plants was more and more
replaced by ammonia, which had indeed been used in parallel since the last quarter of the
19th century. In air-conditioning applications, the replacement of CO2 started in the
midthirties of the 20th century by the new "safety refrigerant" R 12 (e.g. Freon 12, Frigen 12).
The discussion about CO2 as a refrigerant was revived essentially by a patent of Professor
Gustav Lorentzen from 1990 "Trans-critical vapor compression cycle device", patent WO
90/07683. Other impulses came from the works about CO2 as a refrigerant for automotive
air-conditioning systems by G. Lorentzen and J. Pettersen in 1993/94.

Experts in many sectors realized that CO2 had the potential to be an excellent refrigerant for
our present energy awareness and environmental situation. Animated research activities
started at institutes, companies, and universities in order to dig up more than 100-year-old
research results and adapt them to our present abilities with regard to procedures, materials,
lubrication and optimal energy consumption. Various new CO2 applications for refrigeration purposes have been developed recently and have been realized in practise in existing plants. So far, systems with CO2 as the evaporating secondary refrigerant account for the highest percentage, preferably in the deep-freeze range (up to -50°C), e.g. in freezers for bread, cakes and pastries as well as for other food products, in supermarkets (many in Sweden), frozen food storage facilities and artificial icerinks (e.g. in the southern, German-speaking region). As a rule, the cooling and recondensation of the secondary refrigerant in larger plants is done by one-stage or twostage NH3 refrigeration systems. Two-stage CO2/NH3 cascade plants with CO2 compressors on the low pressure side and NH3 compressors on the high pressure side have also been realized already, e.g. for freezer operations. Apart from that, systems for automotive airconditioning systems and heat pumps with CO2 as the refrigerant have been developed for the operation in the supercritical range.

Apart from the ecological benignity of these new CO2 applications, there are also solid
economic advantages, such as better product quality at lower temperatures, even secondary
refrigerant temperatures (artificial ice-rinks), better heat transfer coefficients, smaller low
pressure compressors, smaller pipe dimensioning, optimisation of the energy consumption.
The technical details and technological advantages of these new refrigeration systems as
well as the physics, chemistry and the physiological properties of the refrigerant and the
secondary refrigerant CO2 will also be discussed in one of the eurammon information papers.