In the year 1892, while making some experiments with an electric furnace, Mr. Thomas Leopold Wilson discovered that powdered coal and lime, mixed together in equal parts, fused under the influence of very high temperatures, and eventually entered into combination, forming the compound known as carbide of calcium. This substance undergoes an energetic chemical action with water - resulting in the formation of lime, and the gaseous hydrocarbon, The action is chemically represented by the following equation: -

Calcium Carbide Water Lime Acetylene Gas.

CaC2 + H2O = CaO + C2H2

It is this gas which has claimed the public attention for the last few years as an illuminant. Compared with the ordinary coal-gas of 16 candles, acetylene shows an illuminating power of 240 candles; in other words, it is fifteen times as rich in light-giving power.

It is only of late, however, that acetylene has come into use, owing to the difficulty in procuring a supply of calcium carbide. Plant for the extensive manufacture of the material has been erected at the Falls of Foyer in Scotland, and great care is exercised over the purity of the lime and coke-dust; the product is a hard, tough, metallic-looking substance, of a dark-gray colour, tinged with purple It is produced very nearly chemically pure, which is an important feature, as impure samples are dangerously explosive when producing gas under cover.

There are a number of firms throughout the country who supply apparatus for the generation of acetylene from calcium carbide; all are of different design and construction, but mainly they rely on two methods of producing the gas. The first practice is the use of a small gasholder, with the usual water seal, but arranged internally for the attachment of a perforated trough or wire basket containing the carbide of calcium. As the gas is consumed, the holder and basket fall to the water-level. The water acting on the carbide readily, acetylene is given off in copious volumes, and the holder rises again owing to the accumulation of gas. Upon the rising of tin-holder, the carbide is removed from contact with water, and the gas-producing action ceases.

The second type of generator is shown in Fig. 665, and consists of a reservoir, having two or more cham-bers connected by pipes or small openings at the bottom. A quantity of water is supplied to one chamber, and carbide of calcium placed in tin-other. Communication between the two chambers is established, the water reaches the carbide, chemical action ensues, and acetylene gas is produced. Finding no outlet, however, the gas begins to exert a pressure, which, acting upon the surface of the water, forces it through the channels back into the water-chamber. The generating action consequently ceases so long as the pressure is maintained. Thus the supply of gas is automatic and constant, fall of pressure admitting water and permitting the production of gas, and a rising pressure ending the generation of the gas by compelling the water to leave the chamber. In this latter method a good system of governing the pressures of the acetylene gas is a necessary concomitant being burnt in Hat-flame burners with very diminutive orifices. It is distinguished from coal-gas by the great absence of any internal blue flame, such as is usually noticed near a gas-burner. An acetylene flame, with a superficial area equal to that of a shilling, will give an illuminating power of 20 to 25 candles. Such an intense light is not congenial to the eyes, and necessitates the use of globes and shades.

In either system, the mode of obtaining the gas is remarkably simple, the apparatus can be managed and worked by any intelligent boy or servant. It is a very clean method of procuring light; and the apparatus is compact and cheap. Many instruments for generating the gas can be charged for making large quantities continuously.

The light obtained from acetylene is a very brilliant white light, the gas

Fig. 665   Acetylene gas Generator.

Fig. 665 - Acetylene gas Generator.

a a. gas-inlet to holder; b b. water Inlets to calcium-carbide chambers; c c, support for calcium-carbide chambers: d d, remov-able chamber-covers.

Hitherto some difficulty has been experienced in providing a suitable burner for acetylene; even with those having exceptionally small orifices, the gas will deposit carbon gradually, till the burner is rendered useless. A device of considerable ingenuity has brought an effective burner into the market. In the steatite tip, about one-eighth of an inch below the orifice for the gas, four small holes are drilled radially into the gas-way of the burner. By this means a small quantity of air finds its way into the gas before ignition, being drawn into the gas-channel by the efflux of the gas. The ignition in consequence takes place at a little distance from the extremity of the steatite tip. The value of the burner described is further enhanced by the use of two jets, placed at an angle that causes the two flames to impinge on each other, tending as it does to produce a steady broad light.

The question of illuminating country houses by acetylene deserves serious consideration. The facility with which the gas can be made, the reduced size of plant required for its generation, and the brilliancy of the product, naturally recommend the system to every investigator of its merits.

On the other hand, then- are two most essential conditions required with the use of this illuminant. The first consists of a very dry and well-ventilated store for the carbide of calcium, as this readily absorbs moisture from the atmosphere and gives off acetylene gas. For this reason, an apparatus which provides for the attachment of charges of carbide in cylindrical vessels to the sides of the generator, as shown in Fig. 6G2, has an advantage, owing to a large quantity being securely imprisoned, yet ready for work immediately it is required.

The second condition referred to, and which should be a conditio sine qua non in regard to the adoption of the system, is the absolute soundness of the gasfittings inside the house. An escape of acetylene gas is fraught with grave consequences. Even in small quantities its effects have proved serious; and every effort -should be made to obtain perfectly-sound fittings. Acetylene gas, when inhaled, acts injuriously upon the haemoglobin of the blood, and consequently is a direct enemy to the human economv.1

1 There is also serious danger of explosion when this gas is used. Any mixture of air and acetylene, in which the latter to within the limits of 3 and 82 per east of the former, to very explosive. So grave is the danger, that in Carbide of calcium can be obtained from the Acetylene I Humiliating Gas Co., at the Falls of Foyer, at a price of 20 per ton. This company has the legal monopoly of making the substance by electrical furnaces, in the United Kingdom. One ton of carbide will produce prartically 11,000 cubic feet of gas; l000 cubic feet of gas will consequently cost I, 13s. 4d. Burners consuming cubic foot per hour will give a light of 25 candles, and few makers care to go above this illuminating power, owing to the uninviting colour of the Haines.