Chapter XXXV: Acetylene and Its Dangers

All details relating to the manufacture of coal-gas, water-gas, or oil-gas, and to the incidental risks both to the worker and the consumer, are well known, having been treated by many reliable authorities. Acetylene gas, however, is a comparatively modern illuminant, growing in public favour, and now that the manufacture of calcium carbide is not confined to the United States, Canada, and the Continent, but is produced also in the United Kingdom, it is probable that the adoption of acetylene will become more general.

For country houses, country churches, railway stations, isolated factories and workshops, Indian bungalows, and other places where a cheap and ready supply of coal-gas or electricity is not available, acetylene will be particularly appreciated. Its uses, however, are more extended. On the Continent many towns are lighted with this gas. The Town Commissioners have expressed satisfaction with it as an illuminant for the town of Boyle. For photographic purposes, carriage lamps, magic lanterns, bicycle lamps, etc., acetylene is largely used.

A brief description of the manufacture will be interesting. The writer, owing to the fact that there are as yet few carbide of calcium manufactories in the United Kingdom, can speak with only a limited experience, but he is indebted for information to the Read-Holliday Acetylene Company, to an article which appeared in the _Public Health Journal_ for 29th September 1900, to one on “Electrical Furnaces” recently published in the _Windsor Magazine_, and to other sources.

The introduction of electrical furnaces capable of producing intense heat has rendered it possible to melt and join together such infusible elements as lime and carbon. When the furnaces are cool, the compound formed is known as “calcium carbide.” If dropped in water it decomposes; some authorities say, almost with an explosion. If simply damped, the decomposition is slower, the product given off being the gas known as “acetylene,”--a colourless gas, stated to contain by weight 24 parts of carbon and 2 parts of hydrogen. In England the electrical furnaces are practically arc lamps on a large scale, the bottom of the furnace being a large carbon block electrically connected to the positive pole of the generator, whilst the upper carbon is connected to the negative. By a simple arrangement the negative pole can be raised or lowered at will, to strike the arc or regulate the intensity of the furnace. A mixture of lime and coke, in the form of fine powder, is thrown into the furnaces for fusion, and when cool it is taken away in lumps ready for use.

Seeing that this industry is one of very modern date, it is of interest to consider whether acetylene gas, during the process of manufacture or in use, is likely to produce injury to health or life. This question may be considered under the following heads:--

(_a_) The inhalation of dust during the crushing processes and in feeding the furnaces.

(_b_) The fumes evolved from the furnaces.

(_c_) The danger of electric shock to the workers.

(_d_) Explosion during the stages of manufacture.

(_e_) Explosion, or risk of inhalation of gas, when in use.

During the operation of grinding carbon and lime, and when feeding the furnaces, more or less fine dust must of necessity arise, unless this is prevented by mechanical appliances of a somewhat expensive kind. Some of this dust will be held in suspension by the atmosphere and inhaled by the workers, but as the work is done in practically open sheds, and as the industry is of comparatively recent origin, it is impossible at present to say whether injury to health is caused. Labourers engaged in quarrying limestone are said to be healthy men. The late Dr Arlidge, when referring to workmen employed about lime-kilns, stated that there are grounds for believing that the carbonic acid of respiration is capable of acting upon lime-dust and ridding the lungs of it.

(_b_) Fumes must of necessity be given off from the furnaces, but mechanical ventilating fans render these harmless.

(_c_) Little fear of electric shock need be apprehended in this country, the voltage being low, although the current is strong--a result attained by the aid of several brushes and heavy copper strips for conveying the current to the carbons forming the furnaces. An interesting article recently published in the _Windsor Magazine_ describes a visit to Niagara Falls, where the largest furnaces in the world are operated, and where, amongst other industries, is found the manufacture of calcium carbide. Furnaces on the arc and incandescent principle are employed. The current enters the building at a voltage of 2200, to be transformed to about 100 volts, which approximates the pressure found in English works.

(_d_) An accident of a serious (but happily a non-fatal) nature recently occurred at works in which the calcium carbide, when cool, is stored in 8 cwt. metal tanks, ready to be sent away. It appears that some moisture had found its way into a returned tank. This was unobserved by a worker, who placed about 4 cwts. of the material into it, screwed the lid down, and left the works for the night. The tank stood about 15 feet from the electric furnace. A mechanical fan for ventilating purposes was running, and caused a current from the direction of the tanks to the furnace. As a natural result, gas was generated in the tank during the night. The workman, before resuming work in the morning, took off the lid, liberating the gas, which was at once ignited by the furnace, causing explosion, and seriously injuring the man. The obvious lesson is, that tanks should be carefully examined for moisture or leakage before filling, and that under no circumstances should the filling be done near the furnaces, but in another room, in which there are no lights and no probability of “sparking” from any electrical machine.

(_e_) On the first adoption of acetylene, accidents happened, giving rise to a general belief that it was dangerous. The following extracts from Orders in Council issued at various times will show that the Government officials were fully alive to this danger, and that from time to time precautions to safeguard the public have been taken. By an Order in Council dated 26th February 1897, certain parts of the Petroleum Acts, 1871–1881, were made to apply to carbide of calcium, and it was laid down that:--

“The label on the vessel containing the carbide of calcium shall
bear in conspicuous characters the words ‘Carbide of Calcium,’
‘Dangerous if not kept dry,’ and with the following caution:
‘The contents of this package are liable if brought into contact
with moisture to give off a highly inflammable gas,’ and with
the addition:--

“(_a_) In the case of a vessel kept, of the name and
address of the consignee or owner.

“(_b_) In the case of a vessel sent or conveyed, of
the name and address of the sender.

“(_c_) In the case of a vessel sold or exposed for
sale, of the name and address of the vendor.”

On the 7th July 1897, an Order in Council amended the Order of 26th February 1897, by prescribing that:--

“Notwithstanding anything to the contrary in the said Order,
the quantity of carbide of calcium which may be kept without a
licence shall be as follows:--

“(_a_) Where it is kept in separate substantial hermetically closed
metal vessels containing not more than
1 lb. each 5 lbs.
“(_b_) Where it is kept otherwise None.”

By a further Order in Council, dated 26th November 1897, it was laid down that:--

“Acetylene when liquid, or when subject to a pressure above
that of the atmosphere, capable of supporting a column of
water exceeding one hundred inches in height, and whether or
not in admixture with other substances, shall be deemed to
be an explosive within the meaning of the Explosives Act of
1875, subject to the following exception; that if it be shown
to the satisfaction of the Secretary of State that acetylene,
declared to be explosive by this Order when in admixture with
any substance, or in any form or condition, is not possessed
of explosive properties, the Secretary of State may, by Order,
exempt such acetylene from being deemed to be an explosive.”

The Order further prescribed that:--

“Whereas by section 43 of the Explosives Act, 1875, it is
provided that Her Majesty, from time to time by Order in
Council, may prohibit, either absolutely, or except in pursuance
of a licence of the Secretary of State under the said Act, or
may subject to conditions or restrictions, the manufacture,
keeping, importation from any place out of the United Kingdom,
conveyance, and sale, or any of them, of any explosive which is
of so dangerous a character, that in the judgment of Her Majesty
it is expedient for the public safety to make such Order.

“And whereas it is in the judgment of Her Majesty expedient for
the public safety that acetylene, when an explosive within the
meaning of this Order, shall be prohibited.

“Now, therefore, in pursuance of the above-mentioned provision
of this Act, Her Majesty is pleased, by and with the advice
of Her Privy Council, to order and prescribe that acetylene,
declared to be an explosive by this Order, shall be prohibited
from being manufactured, imported, conveyed, or sold.”

An Order of the Secretary of State, dated 28th March 1898, provided as follows:--

“Acetylene in admixture with oil-gas in a proportion not
exceeding twenty parts by volume of acetylene in every one
hundred parts of the mixture, when subjected to a pressure not
exceeding one hundred and fifty pounds to the square inch, shall
not be deemed to be an explosive within the meaning of the
Explosives Act, 1875.

“Provided that the acetylene and oil-gas shall be mixed together
in a chamber or vessel before the gases are subjected to
compression.”

Lastly, an Order of 15th May 1900 required:--

“That acetylene in admixture with air or oxygen, declared to
be an explosive by this Order, shall be prohibited from being
manufactured, imported, conveyed, or sold.

“Provided that nothing in this Order shall apply to acetylene
in admixture with air when such admixture takes place only in
a burner or contrivance in which the mixture is intended to be
burnt.

“Provided also that nothing in this Order shall be held to apply
to an admixture of acetylene and air which may unavoidably
occur in the first use or re-charging of an apparatus, properly
designed and constructed with a view to the production of pure
acetylene.”

A Committee of the Society of Arts, London, was appointed to investigate the subject and frame rules for the safe construction of acetylene apparatus, and it is claimed (justly I believe) by manufacturers such as the Read-Holliday Acetylene Company, Lockerby and Wilson Limited, and others, that their apparatus fulfils the conditions laid down by the Committee, and that now their appliances may be used with perfect safety. Messrs Tinker & Holliday, of Huddersfield, who manufacture carbide of calcium, give their assurance that they have sold more than 1000 machines, mostly of a large size, some of 600 lights, and that there has never yet been an accident of any kind. On the other hand, it must be remembered that, as acetylene is more explosive than coal-gas, exceptional care should be taken as to where generators are placed, and to avoid the use of lights where leakage is suspected. Early last November a representative of an acetylene firm visited an hotel in a country town in Derbyshire to inspect the generator. The newspapers state that immediately after striking a match a loud explosion occurred, in consequence of which his face and hand were injured.

The _Chemical Trade Journal_ for 16th June 1900 contains a paragraph of public interest, relating to the safety of calcium carbide, which may perhaps with advantage be here reproduced:

“The large army of insurance agents and adjusters who are now
in Ottawa settling the losses incurred through the recent fire
have lately had before them an object lesson which should remove
any doubts that may have been entertained as to the safety of
storing carbide of calcium. According to a communication we have
received from Mr Andrew Holland of the Board of Trade, Ottawa,
when the fire reached the furnace-room of the Dominion Carbide
Works, everything in it that would burn was consumed. Three pigs
of carbide, however, in three crucibles remained in perfect
condition as evidence that they did not explode. The grinding
and mixing department and warehouse were in another building,
and every effort was made to prevent the fire from reaching it;
but the very strong wind blowing, and the vast rush of flame,
enveloped all the buildings in the vicinity, and they were in a
few minutes reduced to ruins. In the carbide warehouses there
were 15 tons of carbide, packed in rolled steel cans with screw
covers. When the floor burned, the carbide dropped through into
the cellar, in which a foot of water had collected from the
firemen’s hose. Here was an ideal combination for an explosion,
if carbide is an explosive. Several cans were broken in the
fall, owing to the intense heat having opened the seams, and the
carbide was dumped into the water. Gas was generated in immense
quantities, but it simply burned with a low steady flame, making
less show than two cartloads of coke on fire in the immediate
vicinity. Had the cellar been dry, the carbide could have been
all saved after the fire; but it continued to soak up the water
and make gas for some days, and the burning gas kept the carbide
so hot, that it could not be handled. As it was, about a ton
of it was shovelled out and packed in new cans. Two of the
cans were dug out whole from the hot mass, and saved with the
carbide, though they were burned like old, worn-out stove-pipes.
The insurance agents admit that they have had a practical
demonstration which had convinced them how much the ‘risks’ of
calcium carbide have been over-estimated.”

It is claimed by the manufacturers of acetylene that it possesses certain hygienic advantages over other gases, these being--a less consumption of oxygen, a less addition of carbonic acid to the atmosphere, less heating of the air, and freedom from sulphur compounds. The illumination is stated to be brilliant, but not injurious to the eyes. On this point, however, it does not appear that oculists in this country have pronounced definite opinions, although individual medical practitioners have reported favourably. Dr W. A. M’Keown, in his _Treatise on Unripe Cataract_, in a chapter on “Suitable Light and Optical Aids,” says: “Fortunately, however, it is now within the power of the surgeon to whom the electric light is not available to have acetylene light, an illuminant at least as good as the electric light, and very well borne by the eyes.”

An article by Professor Thomas Oliver, published in the _British Medical Journal_ of 23rd April 1898, and entitled “Acetylene, the New Illuminant, and the Dangers arising from its Inhalation,” is probably the only authoritative statement yet published dealing with the physiological effects of acetylene gas. In a brief paper such as this, many details describing the methods of experiment adopted by Dr Oliver must be omitted, but the following is an attempt to summarise the conclusions arrived at by him:--

A mixture of air and acetylene commences to be explosive when it contains 5 per cent. of acetylene (Captain Thomson, H.M. Chief Inspector of Explosives, thinks 3 per cent.), whereas it requires the presence of 8 per cent. of coal-gas to make a similar mixture explosive. It is therefore more explosive than coal-gas. Acetylene has an excessively pungent and disagreeable odour, but this, although a disadvantage in some ways, acts as a warning to individuals of its presence. Generators for private mansions, etc., should be placed in the open air, or in a covered shed open at the sides. In the case of coal-gas and water-gas, death supervenes by asphyxia, owing to the carbon-monoxide entering into extremely stable combinations with the hæmoglobin of the blood. If a rabbit is placed in a bell-jar into which ordinary air and acetylene are pumped, the animal for a long period experiences little inconvenience. If atmospheric air is excluded, and acetylene only admitted, symptoms gradually and slowly develop. After more lengthened exposure to acetylene than that which is necessary for coal-gas, the animal becomes intoxicated, stupor stealing over it, apparently painlessly. When somnolence has been induced and asphyxia not pushed too far, the rabbit, if placed in atmospheric air, shortly afterwards moves about in as lively a manner as if it had not been interfered with. Should the inhalation, however, have been pushed further, and the animal be deeply narcotised, death may ensue. In the minor stages of asphyxia, vascular tension is maintained, but in the deeper stages the vessels are so deeply contracted, that it is almost impossible to obtain a drop of blood. On spectroscopic examination, the blood of a rabbit at different stages of intoxication from acetylene always exhibits the well-marked bands of oxyhæmoglobin, but, unlike the blood in coal-gas poisoning, it is capable of undergoing reduction. In this respect it behaves like ordinary blood. If asphyxia caused by acetylene is not too profound--and under ordinary domestic circumstances it would not be a pure acetylene atmosphere that would be inhaled by an individual, but one mixed with a large proportion of common air--the danger to life seems to be less than it would be in coal-gas poisoning, and the prospect of recovery by removal to atmospheric air greater. Death may supervene, however, if the inhalation has been lengthened, and atmospheric air excluded. In the treatment of unconsciousness caused by the inhalation of acetylene gas, it is necessary to remove the individual into the open air, and to try artificial respiration.

Since this brief article was framed, a handbook for the student and manufacturer has been published by Professor Vivian Lewis, dealing in an exhaustive form with everything relating to acetylene. It is illustrated profusely, and doubtless will become a standard book of reference.

In November 1900, the Foreign Office published a Consular Report by Dr Frederick Rose, H.M. Consul at Stuttgart, on “The Rise, Progress, and Present Condition of the Carbide and Acetylene Industries in Germany,” containing statistics and detailed information of considerable value, but which cannot well be here reproduced. It is shown that thirty towns or villages in Germany, with populations varying from 6000 to 382, are lighted by acetylene. In Berlin the Imperial Post Office has made a beginning by lighting two of its branch post offices with this gas, and has installed an apparatus with sixty jets in the head post office. In July 1898, 62,000 jets of acetylene were installed in Germany. In the first months of 1899 the number had increased to 170,000. Reference is made to a new application of calcium carbide in the production of pure metals from their ores by its use as a reducing agent; to the manufacture of lampblack, it being stated that acetylene gives three to four times as much lampblack as good oil-gas; and to an invention which utilises carbide for the production of converted steel, as well as for hardening armour-plate after Harvey’s process.

On 1st December 1900, _The Public Health Engineer_ devoted the whole of its issue to acetylene, and as the article gives in detail descriptions of generators and other appliances made by practically all recognised firms, together with a statement of what is claimed in regard to safety and economy in use, it may be helpful to mention this publication, for the benefit of inquirers.

HAMILTON P. SMITH.