Carbonic Acid Engines

Updated: 14 Jan 2019

Lilienthal engine added
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Now and again, in the very early history of motor cars and aeroplanes, you will encounter references to a "carbonic acid motor", usually quickly followed by a statement that the machine in which it was installed was a total failure. Information on this method of deploying power is very hard to come by, but here are a few gleanings.

Carbonic acid is an old name for carbon dioxide. A carbonic acid motor (or engine) is driven by pressure which may simply come from a reservoir of compressed gas, or be produced by evaporating liquified carbon dioxide. A liquified gas takes up much less space than its compressed gaseous equivalent, giving the possibility of greater energy storage. Carbon dioxide is easily liquified, unlike the so-called "permanent" gases such as nitrogen and oxygen, which require more energy and more complex machinery to liquify, and are much harder to store for any length of time.

All gases have a critical temperature; below this temperature, the gas can be liquefied by the application of pressure alone. Carbon dioxide has a critical temperature of 31.1 °C, and so can usually be liquefied just by compression. The critical temperatures of oxygen and nitrogen are -118°C and -146°C respectively, and they are therefore much harder to liquify, as considerable pre-cooling is needed as well as compression.

Calling carbon dioxide "carbonic acid" is an obsolete usage. Nowadays carbonic acid refers to H2CO3, a weak dibasic acid formed when carbon dioxide dissolves in water; this acid exists only in solution.


The history of CO2 engines begins early in the 1800's, when experimenter first liquified and solidified carbon dioxide. They discovered- sometimes through catastrophic explosions- that if CO2 was chemically generated in a sealed vessl, enormous pressures were generated. Using CO2 to replace steam in engines looked very promising.

One of the famous accidents occurred when Adrien Thilorier was experimenting with liquid CO2 in Paris. A cast-iron vessel exploded, and "tore off both legs from the unfortunate M Hervey."

The incident is mentioned by the famous chemist Justus Liebig in in a 1843 letter:

"...This, however, cannot be accomplished without considerable danger. A melancholy accident occurred at Paris, which will probably prevent for the future the formation of solid carbonic acid in these large quantities, and deprive the next generation of the gratification of witnessing these curious experiments. Just before the commencement of the lecture in the Laboratory of the Polytechnic School, an iron cylinder, two feet and a half long and one foot in diameter, in which carbonic acid had been developed for experiment before the class, burst, and its fragments were scattered about with the most tremendous force; it cut off both the legs of the assistant and killed him on the spot. This vessel, formed of the strongest cast-iron, and shaped like a cannon, had often been employed to exhibit experiments in the presence of the students. We can scarcely think, without shuddering, of the dreadful calamity such an explosion would have occasioned in a hall filled with spectators."

Wikipedia provides more details, though they do not quite line up with Liebig's account: "On 30 December 1840, Osmin Hervy, who prepared scientific demonstrations for lectures at the School of Pharmacy in Paris, was operating one of Thilorier's machines when the gas-generating cylinder exploded. Shrapnel broke Hervy's legs, one of which had to be amputated; he died of infection a few days later." Contemporary reports show that this is what actually happened.


In 1884 or 85 the US Navy exhibited a Lay-Haight torpedo, powered by a reservoir of compressed carbonic acid that worked a Brotherhood engine connected to the screw. The torpedo was wire-guided and exploded from the shore, so was presumably intended for coastal defence only.


The aviation pioneer Otto Lilienthal made many successful gliding flights before he was killed in a gliding accident on August 1896. He inspired the Wright brothers. Like several others before him, Lilienthal never quite abandoned the idea that flapping wings was the key to motion. In 1893 and again in 1896, he built gliders with flapping wings in the ornithopter fashion. Each machine had a lightweight carbonic acid engine that produced about two horsepower (1.5 kilowatts). The engine was supposed to make the wing tips flap up and down and move the aircraft forward. Neither model was successful.

Left: The Lilienthal glider: 1894

Lilienthal was also aiming for powered flight, on a flapping-wing basis. At the bottom of the glider there is a white cord holding two bell-cranks together; this cord was to be replaced with a carbon dioxide motor that would pull the wings down when it operated.

Photograph courtesy of Bernd Frieboese, Jan 2019

Left: The Lilienthal carbon dioxide motor: 1894

Nothing is currently known of this engine beyond its outside appearance. Since the wings were connected to it by cords it presumably was a single-acting engine giving a pull action only. The black box at the bottom appears to contain the valves, which are apparently operated by the brass rod. The curved trigger on top appears to control the valves and so stop or start the engine.

Nothing is currently known of the operating pressure or the construction of the carbon dioxide reservoir.

Photograph courtesy of Bernd Frieboese, Jan 2019

Left: The Lilienthal carbon dioxide motor: 1894

There is a tantalising glimpse of a pressure gauge at lower right.

Photograph courtesy of Bernd Frieboese, Jan 2019


Left: A carbonic-acid car by The New Power Company: 1899

The New Power Company was based in Trenton, New Jersey.

The following is extracted from The English Motor-Car Journal, 1899

"The carbon-dioxide is admitted to the engines under the full vapour tension of the liquid under normal temperature, the gas being heated to a high temperature before being admitted to the cylinders of the engines. One company is reported to have secured a factory at Kingston, N.Y., in which locality several very extensive cement factories are operated. The reputed cause for the selection of this centre as a site for the factory is that arrangements have been made with these cement companies for the gathering and storing of the carbon-dioxide generated during the burning of the cement."

A telling point there is the need to heat the CO2 before it could be applied effectively. Obviously some extra fuel would be needed for that, so the vehicle was not powered entirely by carbonic acid.

According to The Horseless Age, Oct 1898, the liquid CO2 was stored in the tubular frame of the New Power Company vehicle and heated to 90 degrees (Fahrenheit or Centigrade?) by a flame generated by "Sestalit" a patent solid fuel of the era. "The difficulty hitherto experienced with carbonic acid gas, when used for power, has been that the rapid evaporation would cause the valves to freeze. This difficulty the inventor claims to have overcome through a new valve which positively cuts off the current from the retaining cylinder at every stroke. One lever only is used for steering and regulating speed, while a second is required for reversing the motor."

"Sestalit" was a produced by the United States Fuel Company, who published a book on it called "The Marvelous Fuel, Sestalit" in 1890. They appear to have been primarily a coal mining company. The fuel was patented by Albrecht Pagenstecher in August 1890; see US patent 435,076. Sestalit consisted of hundred pounds of pulverized charcoal or coke, 3.5 pounds of saltpeter, (potassium nitrate) 3 pounds of starch, and 0.5 pounds of powdered brown sandstone, made into a paste with water and then pressed into moulds.

It was claimed that Sestalit could be lit with just a match, and then burnt "slowly and continuously without flame, smoke, or noxious gases and emitting an intense and uniform heat." It would still be a nuisance to have to light up the CO2 heater before setting off, but but a lot less trouble than the traditional paper, wood, and coal method of building a fire. Sestalit was intended for small-scale heating applications like sad-irons and foot-warmers.

Left: The Gibson carbonic-acid car: 1899

A car powered by carbonic acid was developed by Charles Gibson of Jersey City, New Jersey. There is a chain or belt drive to the rear axle, the engine being installed in the rear of the body.

From The Horseless Age, May 31, 1899:

"The expansive power of carbonic acid is titanic, but two chief difficulties have stood in the way of its adoption for power purposes--the inability of inventors to control it and prevent the valves from freezing up owing to its too rapid expansion, and the high cost of the substance."

Gibson's car claimed to have eliminated the problem of freezing valves; this was clearly an endemic problem with the technology. The article thought that carbonic acid could be economically manufactured in quantity given enough demand for it.

It is not clear whether the freezing problem was caused by ice, originating from contamination with water, or if the carbon dioxide itself was freezing. This is entirely possible (and probably the more likely explanation) as solid carbon dioxide, otherwise known as dry ice, forms readily when liquid carbon dioxide is evaporated.


Left: An article on railway signals powered by carbonic acid.

An intriguing reference to carbonic acid, but with no real information at all. Was the gas piped to each signal, or carried there in bottles? Presumably it was in liquid form to increase the power storage density, otherwise they might just as well have used compressed air.

I have never heard of this system of signalling before- it cannot have made much impact.

From Model Engineer & Electrician for 26 May 1904, p489


In 1906 the Romanian aeronautical experimenter Trajan Vuia was living in Paris and testing a small bat-like monoplane with a tractor propeller. The pilot sat well below the wing on a framework with a four-wheeled undercarriage. It was driven by a carbonic acid motor, of which no details have so far been found, except that it was of inadequate power. (A later monoplane was powered by 24hp Antoinette petrol engine) Some short hops from level ground were made, the longest being 24 metres. Proper flight was not realised, but the machines are considered to be the immediate ancestors of the monoplanes which appeared in Europe before World War 1.


Left: Cetonia carbonic acid engine for model aeroplanes

This sophisticated-looking 8-cylinder radial engine was advertised in 1911. Acccording to an article in Flight on 2 Septenber 1911, the engine could be supplied in either fixed (crankshaft rotates, cylinders stay still) or rotary (crankshaft stays still, cylinders rotate) format. The bore was 19mm and the stroke 28 mm. The crankshaft was mounted in ball-bearings. When officially tested at the Conservatoire des Arts et Metiers in Paris, it gave 1.03 horsepower at 1710 rpm for one minute, which seems a pretty hefty output for powering model planes.

The carbon dioxide was carried as a liquid in a steel cylinder containing about 1 kilogram, which underlines that it was meant to power rather large and heavy models. Worse still, it was necessary to carry on board a tank of hot water; the CO2 passed through coiled pipes in this to prevent it solidifying into "snow" on expansion, and choking everything up.

In this view it looks as though the supply pipes are being led straight into the top of the cylinders, but in fact the small cylinders they connect to are the tops of the valve chests. Nothing is known about the valve arrangements but from the shape of the valve-chests they were almost certainly of the piston type.

From Flight for 26 Aug 1911

Left: Inside the Cetonia engine

The eight connecting-rods appear to be connected to a ring around the crank-pin. The eight rods driving the valves are attached to a single eccentric on the crankshaft. The CO2 pipes are not shown, but were fed from a central manifold.

From Flight for 2 Sept 1911

Left: Cetonia heating system

Clearly this not going to be a light-weight power source.

Note the filler and drain plug on the hot water box.

From Flight for 2 Sept 1911

Further details are given in an article that appeared in Flight on 3 Feb 1912. The engine described above is the A -type, with an inclusive price in France of 225 Francs. Types B (1/2 hp) and C (1/4 hp) were crossed out in the French catalogue that Flight received, and so were presumably no longer offered. The temperature of the hot water was supposed to be 90 degC; presumably that was the starting temperature and it cooled rapidly in operation.

Left: Model biplane with Cetonia engine

The model weighed a hefty 17.7 kg, of which 4 kg was the complete CO2 power-plant. It had a propellor 0.85 metre in diameter, and it flew at 29 mph.

From Flight for 2 Sept 1911

The designer of the Cetonia engine was a Monsieur Poterin du Motel. That name raised an eyebrow; it is generally believed that Mademoiselle Stéphanie-Félicie Poterin du Motel was the woman over which the famous mathematician Evariste Galois fought the duel in which he was killed at the age of 20, in 1832.

Further searches for the name revealed H Poterin du Motel, the author of an 1899 textbook on life insurance, and perhaps more promisingly, a Jean Georges Marie Poterin Du Motel who took out British patent 147,656 for life-saving equipment in 1921.


Left: Nomie carbonic acid engine for model aeroplanes: 1911

At present nothing is known about this 3-cylinder rotary engine except for this advert.

From Popular Mechanics November 1911

The ad copy states that the engine has a 18-ounce fuel tank, that somehow holds 1170 pounds (about half a ton) of CO2. I feel a decimal point may have gone astray- 1.17 pounds sounds a bit more like it. Note that it was supposed to also run on compressed air or steam.

I had grave doubts about the actual existence of "Captain Wild the aeronaut" but I was wrong. He was a well-known balloon-racing man, and you can read about his exploits in the Los Angeles Herald. (Volume 36, Number 47, 17 November 1908) The Nomie engine was less famous. It was advertised again in Popular Mechanics the next month, and again in May 1912, but then seems to have disappeared.


Left: Carbon-dioxide powered lifeboat

My first thought was that this sounds like a frighteningly undependable means of life-saving. All those CO2 cylinders would have to be constantly checked for leaks and falls in pressure; was the ship supposed to carry around its own CO2 tanks for continuous topping-up? Having said that, modern life-rafts are often inflated by carbon dioxide or nitrogen cylinders, so perhaps it's not so daft after all. The system does not appear, however, to have ever been used for propulsion, so far as I can discover.

On the other hand, (so to speak) using manual power to compress air and keep the engine running sounds very questionable because of the high energy losses as heat when compressing a gas. The air might be hot when it entered the storage cylinder, but would soon cool down, and the heat energy would be lost.

From Popular Science for Feb 1934

The carbon-dioxide engine appears to be of the two-cylinder horizontally opposed type. One wonders if there were any provision for stopping it freezing up as the carbon-dioxide expanded; any water vapour in the CO2 would congeal and clog up everything disastrously.


This sort of motor must be quite obsolete, no? No. Certainly, typing "carbonic acid motor" or "carbonic dioxide motor" into a search engine will (at the time of writing) yield nothing. The result is quite different if you use "CO2 motor". You will find that modern carbonic dioxide motors are used to power model aeroplanes. Advantages include low noise output and no flammable fuel.

A small metal reservoir is charged with either liquid or gaseous carbon dioxide under pressure. This powers a motor that looks very much like a small glowplug engine. There is a valve at the top of the cylinder usually operated by a protrusion from the crown of the piston. Exhaust is via a uniflow port uncovered by the piston at the bottom of its stroke. Fins are provided, just as on a glowplug engine, but here the purpose is not cooling but to stop the engine cooling down too much as the CO2 expands.

Left: Two CO2 motors for model aircraft.

One pipe runs from a non-return filler valve to the reservoir, and the other takes the CO2 to the engine.

Image taken from the website of Davis Diesel Development. (with permission, I might add) See link below.

CO2 motor links: Do not miss the historical overview in the "CO2 motors" section. which shows some fine CO2 engines, including a V12!

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