How the dissolved acetylene cylinder was invented: from Willson's carbide in 1892 and the explosions of 1896 to Janet's porous mass and acetone in 1901

The dissolved acetylene cylinder is one of the oldest pieces of chemical engineering still in daily use, and it exists because acetylene nearly put itself out of business within five years of becoming cheap. Between Willson's discovery of a commercial carbide process in 1892 and a British Home Office order in 1901, the gas went from novelty to banned explosive to safely bottled fuel. The porous mass and the acetone inside every cylinder KIGL fills are not packaging; they are the two halves of the invention that made the product legal to sell. This page tells that story from the primary sources.

Acetylene had been known since Edmund Davy's announcement of 1836 and Berthelot's naming and systematic study from 1860, and Wöhler had made calcium carbide in 1862. None of that made it an industrial gas. What did was an accident in May 1892 at Spray, North Carolina, where Thomas L. Willson, trying to make metallic calcium in an electric furnace, produced a lump that gave off a flammable gas in water. His patent, US 492,377, issued in 1893. Henri Moissan made calcium carbide independently in Paris in 1892 (Comptes rendus 1892, 115, 1031), and Maquenne made barium carbide, also in 1892. The date is often printed as 1893; it was 1892. Within a few years carbide was being made in quantity, and acetylene — which burns with a brilliant white flame — was lighting towns.

Acetylene as a lighting gas had a storage problem. It could be generated at the lamp from carbide and water, but anyone wanting to carry it compressed in a cylinder, like coal gas, was compressing a gas that decomposes. In 1896 three explosions settled the matter: at Pfleghar and Son in New Haven; at one of R. Pictet's works; and at the Isaac factory in Berlin, with fatalities. Marcellin Berthelot and Paul Vieille then showed what made acetylene different from every other fuel gas: compressed or liquid acetylene could be exploded by a spark, a hot wire or a detonator with no oxygen present at all (Comptes rendus 1896, 123, 323; 1897, 124, 1000). The gas carried its own energy — a heat of formation of about +227 kJ/mol — and could release it by breaking down to carbon and hydrogen.

The regulatory response was immediate:

Acetylene could still be generated and used at very low pressure close to where it was burned, which is how carbide lamps and small generators survived; but a portable, compressed supply was illegal in the two largest European markets. The idea of an upper pressure limit for acetylene, which survives today in the Indian free-state limit of 0.612 atm in IS 14814:2023, starts here. The liquid acetylene page explains why the gas cannot simply be bottled as a liquid.

The rescue took four years and four contributions:

Each piece was necessary. Solubility meant a cylinder could hold far more acetylene at modest pressure than as free gas — the 300 volumes page explains what the real figure is. Berthelot and Vieille's work meant the solution itself was not an explosive at the pressures needed. But acetone alone leaves a gas space above the liquid, and it slops about. The porous mass removed the gas space by dividing the cylinder into pores too small for a decomposition flame to pass, and held the acetone evenly through the volume. Janet's cylinder — porous mass, acetone, dissolved acetylene — is the device in use today; the Gas Cylinders Rules 2016 define it in nearly the same terms in Rule 2(xix), as a cylinder holding a porous mass, a solvent and at least enough acetylene to saturate the solvent at atmospheric pressure and 15 °C.

The British Home Office order of 10 April 1901 permitted the manufacture of dissolved acetylene, and the industry restarted in Britain on the new technology. In the United States, P. C. Avery's work from 1904 and the Concentrated Acetylene Company, which became the Prest-O-Lite company in 1906, put the cylinder into commercial service, at first for vehicle and marine lighting. The copper rule arrived in the same years: the Lemberg railway station lighting explosion, Grittner's study of copper acetylide (Z. Kalziumkarbidfabrikation u. Acetylen 1899, 3, 106) and the Budapest Acetylene Congress of 1899 established that copper and acetylene form an explosive acetylide, which is why Indian rules now cap cylinder valves at 70 percent copper and the code of safety avoids copper alloys altogether, as the copper and acetylene page explains.

The dissolved acetylene cylinder arrived just as acetylene lighting peaked. As compiled by S. A. Miller (1965), 465 towns, 227 of them French, used acetylene for public lighting by 1911, after which the number fell rapidly against the Welsbach gas mantle and the tungsten-filament lamp. The gas was saved by metalworking. Le Chatelier showed the oxy-acetylene flame in 1895 (Comptes rendus 1895, 121, 1144); Edmond Fouché developed oxy-acetylene welding from 1903 (British Patent 6944/1903); and Jottrand demonstrated the first oxygen cutting blowpipe at Liège in 1905 (British Patent 18,897/1905). The cylinder made the flame portable: a welder could carry acetylene to the job instead of building a generator beside it. Lighthouses kept acetylene lighting longest; it was pioneered there by Gustaf Dalén of the AGA company, later a Nobel laureate. The market shift is traced on uses of acetylene gas.

The porous mass has changed more than anything else in the cylinder. Early fillings were charcoal, kieselguhr, asbestos and other loose or granular materials. Monolithic masses, cast in place, displaced them; in North America the predominant mass by the 1960s was calcium silicate formed in situ from lime and silica, with porosities of about 90 to 92 percent becoming current, as compiled by S. A. Miller (1965). Indian law today allows porosity between 75 and 92 percent (Gas Cylinders Rules 2016, Rule 37(ii)). The legacy masses are a modern concern: a 2010 investigation by HSE staff of a cylinder explosion in Great Britain involved a 75-year-old cylinder with a charcoal mass, and the operator then withdrew its charcoal-mass cylinders; older masses may also contain asbestos.

What has not changed is the principle. The cylinder is safe because the acetylene is in solution, the solution is spread through a fine porous structure, and the amount of acetylene is matched to the amount of solvent. Rule 37's explanation in the Gas Cylinders Rules 2016 states the two-sided constraint Janet's design created: too much solvent can make the cylinder hydraulically full and burst it on heating; too little leaves it less resistant to decomposition from a flashback. Filling discipline — weighing every cylinder and keeping its solvent correct — is the modern form of the 1901 invention.