All researches on this subject point to the fact that something under one per cent. only of carbon monoxide in air renders it fatal to animal life, and this at first seems an insuperable objection to the use of water gas, and has, indeed, influenced the authorities in several towns, notably Paris, to forbid its introduction for domestic consumption. Let us, however, carefully examine the subject, and see, by the aid of actual figures, what the risk amounts to compared with the risks of ordinary coal gas.
Many experiments have been made with the view of determining the percentage of carbon monoxide in air which is fatal to human or, rather, animal life, and the most reliable as well as the latest results are those obtained by Dr. Stevenson, of Guy's Hospital, in consequence of the two deaths which took place at the Leeds forge from inhaling uncarbureted water gas containing 40 per cent. of carbon monoxide. He found that one per cent. visibly affected a mouse in one and a half minutes, and in one hour and three quarters killed it, while one-tenth of a per cent. was highly injurious. Let us, for the sake of argument, take this last figure 0.1 per cent. as being a fatal quantity, so as to be well within the mark.
In ordinary carbureted water gas as supplied by the superheater processes, such as the Lowe, Springer, etc., the usual percentage of carbon monoxide is 26 per cent., but in the Van Steenbergh gas—for certain chemical reasons to be discussed later on—it is generally about 18 per cent., and rarely rises to 20 per cent. An ordinary bedroom will be say 12 ft. X 15 ft. X 10 ft., and will therefore contain 1,800 cubic feet of air, and such a room would be lighted by a single bats-wing burner consuming not more than four cubic feet of gas per hour. Suppose now the inmate of that room retires to bed in such a condition of mental aberration that he prefers to blow out the gas rather than take the ordinary course of turning it off—a process, by the way, of putting out gas which is decidedly easier in theory than in practice, especially in his presumed mental condition—you would have in one hour the 1,800 cubic feet of gas in the room mixed with four fifths of a cubic foot of carbon monoxide—the carbureted water gas being supposed to contain 20 per cent.—or 0.04 per cent. In such a room, however, if the doors and windows were absolutely air tight, and there was no fireplace, diffusion through the walls would change the entire air once an hour, so that the percentage would not rise above 0.04; while in any ordinary room imperfect workmanship and an open chimney would change it four times in the hour, reducing the percentage to 0.01, a quantity which the most inveterate enemy of water gas could not claim would do more than produce a bad headache, an ailment quite as likely to have been caused by the same factor that brought about the blowing out of the gas.
Moreover, we are now talking about the use of carbureted water gas as an enricher of coal gas, and not as an illuminant to be consumed per se. and we may calculate that it would be probably used to enrich a 16-candle coal gas up to 17.5 candle power. To do this 25 per cent. of 22 candle power carbureted water gas would have to be mixed with it, and taking the percentage of carbon monoxide in London gas at 5 per cent.—a very fair average figure—and 18 per cent. as the amount present in the Van Steenbergh gas, we have 8.25 per cent. of carbon monoxide in the gas as sent out—a percentage hardly exceeding that which is found in the rich cannel gas supplied to such towns as Glasgow, where I am not aware of an unusual number of deaths occurring from carbon monoxide poisoning.
The carbureted water gas has a smell every bit as strong as coal gas, and a leak would be detected with equal facility by the nose; and I think you will agree with me that the cry raised against the use of carbureted water gas, for this reason, is one of the same character that hampered the introduction of coal gas itself at the commencement of this century.
We must now turn to the chemical actions which are taking place in the generator of the water gas plant, and these are more complex in the case of the Van Steenbergh plant than in those of the Lowe type, and, for that reason, yield a gas of more satisfactory composition.
Taking gas as made by the Lowe or Springer process, and contrasting it with the Van Steenbergh gas, we are at once struck by several marked differences.
In the first place the hydrogen is far higher and the marsh gas or methane lower in the Van Steenbergh than in the Lowe process, this being due to the sharper cracking that takes place in the short column of cherry red coke, as compared with the lower temperature employed for a longer space of time in the Lowe superheater. Next we notice a difference of 10 per cent. in the carbon monoxide, which is greatly reduced in the Steenbergh generator by the carbon monoxide and marsh gas reacting on each other as they pass over the red hot surface of coke with formation of acetylene, which adds to the illuminants, this action also reducing the quantity of marsh gas present.
| Lowe gas. | Van Steenbergh gas. | |
|---|---|---|
| Hydrogen | 27.14 | 46.75 |
| Marsh gas | 25.35 | 11.27 |
| Carbon monoxide | 26.84 | 18.65 |
| Illuminants. | 14.63 | 7.59 |
| Ethane | — | 6.82 |
| Carbon dioxide | 3.02 | 0.50 |
| Oxygen | 0.15 | 0.17 |
| Nitrogen. | 2.87 | 8.25 |
| —— | —— | |
| 100.00 | 100.00 |
In the illuminants, if we add the higher members of the methane series present to the olefines, we see they are about equal in each gas, while the low percentage of nitrogen in the Lowe gas is due to more careful working, and could easily be attained with the Van Steenbergh plant by allowing the first portion of water gas to wash out the producer gas before the hopper on top is closed.