General - Explosive Limits of a Gas - Explosive Limits of Acetylene - Danger of Acetylene Installations - Prefect of Police, Paris - Conseil d'Hygiene Publique et de Salubrite Regulations - Explosion of Storage Vessel filled with Acetylene Dissous: Fatal Result - Eire at Acetylene Dissous Works - Bursting of Boiler Tubes caused by Defective Welding : Fatal Result - Acetylene Generator Explosion - Acetylene a great Poison - Acetylene Accidents in France.

When an accident has taken place it is generally too late to remember, at least so far as that special occurrence is concerned, that acetylene is the most explosive and, therefore, also the most dangerous gas yet known, when dissolved, more so than in its gaseous form.

The explosive limits of a gas and the range of explosibility are influenced by various circumstances, such as manner of ignition, pressure and other conditions. Le Chatelier and Eitner have obtained the following results: -

Explosive Limits of Acetylene mixed with Air

(Le Chatelier).

It appears, therefore, that no explosion of acetylene can proceed past an orifice of 0.5 m.m. in diameter.

Percentage by Volume of Combustible Gas in a Mixture of that Gas and Air Corresponding with the Explosive Limits of such a Mixture (Eitner).

A mixture of acetylene and air becomes thus explosive (will explode if a light is applied to it) when only 3.35 per cent. of the mixture is acetylene, while a similar mixture of coal-gas and air is not explosive until the coal-gas reaches 7.9 per cent. of the mixture. And, again, air may be added to coal-gas, and it does not become explosive until the coal-gas is reduced to 19.1 per cent. of the mixture; while, on the contrary, if air is added to acetylene, the mixture becomes explosive as soon as the acetylene has fallen to 52.3 per cent. Hence the immense importance of taking precautions to avoid, on the one hand, the escape of acetylene into the air of a room, and, on the other hand, the admixture of air with the acetylene in any vessel containing it or any pipe through which it passes. These precautions are far more essential with acetylene than with coal-gas.

The danger is, however, materially increased, especially with acetylene installations for illuminating purposes, as they are generally delivered under the most impressive assurances that there can be no danger whatever, and under that impression the apparatus is left, for daily manipulation, in the hands of persons who are entirely ignorant of the dangerous nature of the gas and the construction of the apparatus, and being more or less used to the easy handling of the ordinary gas, cannot or will not understand restrictions, but in case of the apparatus getting out of order, in their own self-confidence, and with the best intentions, take steps to put it in order, which may have serious results.

It is easy to forget that by placing the acetylene apparatus in the house a more or less dangerous result may always be expected, so also by careless and unskilled manipulation of the plant, or by natural wear and tear, or by corrosion or rust, which scarcely can be avoided, or by using inferior material in order to lower cost of production, all of which will sooner or later produce leakage, and cause an explosion as soon as the room, filled with the extremely small quantity of acetylene required, is entered with a light; or the gas may pass into another room, where a candle or an open fire is burning, causing the same result. Consequently, from a point of safety, an acetylene plant can only thus be considered free from danger when it is placed in a separate house, so constructed that the apparatus can be attended to from outside; but such a desire can scarcely be fulfilled.

The Bulletin des Holies, in its September part, 1908, states that the Prefect of Police, Paris, has, upon the suggestions of the Conseil d'Hygiene publique et de Salubrite, circulated additional regulations in reference to acetylene generators, amongst which may be mentioned, that the manipulation necessary for filling and emptying the generators must be done during daylight. The room in which the acetylene plant is installed must not be entered with light. In the vicinity of the door to the plant-room must be affixed in a visible manner a board containing, in large letters, the following inscription: "After the daily attendance admittance prohibited."

Even with the utmost care accidents will happen, and they will more forcibly enforce a lesson than years of study. For this reason the following accidents are related: -

Explosion of a Storage Vessel filled with Acetylene-Dissous -

Fatal Result.

Dr. Paul Wolff, in the Zeitschrift fur Calcium Carbid-Fabrikation, Acetylene und Klein Beleuchtung, No. 4, 1908, gives the description as follows: -

"Unloading cylinders containing acetylene-dissous one was suddenly dropped, falling with the closing valve upon the stone pavement, with the result that two explosions followed quickly, one after the other, causing great injury to four persons, one of which succumbed after a few days."

Fire at an Acetylene-Dissous Works.

In its May number, 1908, the Zeitschrift fur Comprimirte Gase describes the fire at the Acetylene-Dissous Works at Dose, Quxhaven, on the 28th May, 1908: -

"The Cuxhavener Company had recently acquired a system for welding by acetylene-dissous, probably from the Compagnie Francaise de l'Acetylene-Dissous. On the day of the accident an engineer of the said French company was filling one of the cylinders, under a pressure of fourteen atmospheres, and having finished, he screwed down the valve, when an explosion took place, setting fire to the works. He had, happily enough, already cut off the connection between the gas generator and the filling place, otherwise the entire works would have been blown to pieces."