This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol3", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
Acetylene lighting, like gas and electric lighting, is distinctly practical. It is now quite beyond the experimental or doubtfully new stage, and those undertaking this work are, or should be, able to give guarantees that will satisfy the most particular. In regard to expense, it can be worked out, theoretically, that acetylene costs the same as coal gas at 2s. 6d. per thousand for a given degree of illumination, but this figure fails in practice when allowance is made for the several extra small expenses and waste that are experienced. If the comparative cost is raised a shilling, to 3s. 6d., then this should prove correct under all ordinary conditions, and include for interest on the outlay incurred in erecting the installation. This price, needless to say, is very low for a good illuminant in isolated country houses. It will even compete with coal gas in villages and small towns, for this seldom costs less than 5s. per thousand feet and often more, and as a rule it leaves much to be desired in its illuminating qualities.
In regard to the attention an acetylene plant needs, and its safety, the average generator admits of everything being done by a gardener, or other quite unskilled person, in from ten to fifteen minutes daily. As a rule a plant is installed of a size that needs daily attention, but if money is spent in having a larger size, then the few minutes attention needed will be bi-weekly or weekly, according to the charge of material (calcium carbide) that the generator will take. There is not the least danger to be feared unless the attendant does one dangerous thing, this being to take a naked light to the generator shed - the gas-making house. There have been accidents, too many, but in every single case it has been the result of gross carelessness, usually attempting to recharge the generator (this having been forgotten in daytime) after dark, using a naked light to do the recharging by. A person may even do this risky thing with impunity with some generators; and in any case if a lamp is stood on the ground about 12 feet away from the generator shed it affords light enough for the simple task that recharging is. Where accidents have occurred lights have been taken into the shed.
The light afforded by acetylene is doubtless the most pleasing known, and not only may plumbers and engineers push this work in safety and with profit, but there is an enormous field for it almost untouched as yet. As a light, and in its general qualities, acetylene has nothing to rival it.
Calcium carbide (CaC2), from which acetylene is made, is a grey stony substance, formed by fusing together lime and carbon (coke or anthracite coal) in an electric or other high-temperature furnace. The resulting mass, termed an ingot, is then broken into commercial size, and after being picked over is packed for sale.
Acetylene (C2H1) is a gas that is evolved immediately calcium carbide comes in contact with water, the reaction being expressed thus :-
Calcium carbide + water changes to lime + acetylene. CaC2 + H10 = CaO + C2H1
From this it will be seen that the chemical association of calcium carbide and water (which occurs immediately they meet) results in the evolution of acetylene, with plain lime (and excess of water) as a waste product. It may be mentioned here that the resulting lime is quite suited for building purposes, lime-washing, and the many uses that can be found for it on a country estate. Theoretically, the lime would be a monoxide or quicklime, but the excess of water makes it finally appear as a hydrate or slaked lime.
The affinity that the carbide has for water is so great that it would serve as a drying agent. It readily absorbs moisture from the air, and if left exposed for a short time it will be found to have become decomposed, yielding its gas to the atmosphere and leaving a heap of lime behind. On this account calcium carbide must always be kept in air-tight receptacles, not only to prevent the waste that would otherwise occur, but. also to avoid the production of gas in improper places, where the introduction of a light would cause an explosion. Carbide is always delivered in sealed metal drums, which, when opened, are emptied into the user's own receptacle, which should be provided with some kind of removable compression lid with rubber collar to render it air-tight.
As the generation of acetylene is so easily effected by simply bringing carbide and water together, it might be supposed that the generating apparatus would be of an equally simple character. This in a great measure is true, but for the perfect production and control of the gas certain rules have to be observed, introducing some detail in the generator. What may be considered as an ideal set of rules is as follows, and, it should be noted, it is quite easy to observe all these in a proper manner when erecting an installation, 1. A generator, whatever its size, should be charged in a few minutes by a person unskilled in mechanics or technical knowledge.
2. Part of the generating plant should consist of an adjustable gasholder, to receive the gas as generated, and deliver it to the house services as required.
3. Every generating plant should be provided with a positive working escape pipe, to allow of excess gas escaping into the open air should the apparatus be carelessly used or excessively overcharged.
4. The gasholder bell should not carry carbide chambers or anything that will cause a varying weight, and consequently a varying pressure of gas in the service pipes.
5. The water of the gasholder must not be used for anything else. Its level should be constant.
6. There should be no operating parts inside the gasholder. All working parts should be exposed to view.
7. Automatic generators should have no "gear." A ball valve and water cock with lever head operated by the holder bell - or something equivalent to this - is sufficient.
8. In every case when the water and carbide come together the proportion of carbide that is wetted should be submerged and remain submerged. The generation of gas is accompanied by heat, which can have a bad effect on the quality of the gas. This rule provides for cool generation, and a gas as clean as crude gas can be.