49. What is hydrogen?

Hydrogen is an elementary gas, and is the lightest of all known bodies.50. Will hydrogen support animal life?

It will not. It proves speedily fatal to animals.51. Will hydrogen support combustion?

Although it will burn, yielding a feeble bluish light, it will, if pure, extinguish a flame that may be immersed in it. Hydrogen will therefore burn, but will not support combustion.52. Why will hydrogen explode, if it will not support combustion?

When hydrogen explodes it is always in combination with oxygen, or with the common air, which contains oxygen. Two measures of hydrogen and one of oxygen form a most explosive compound.

"As smoke is driven away, so drive them away: as wax melteth before the fire, so let the wicked perish at the presence of God."—Psalm xlvi.

53. Why does hydrogen explode, when mixed with oxygen, upon being brought in contact with fire?

Because of its strong affinity for oxygen, with which, upon the application of heat, it unites to form water.54. Where does hydrogen chiefly exist?

In the form of water, where it exists in combination with oxygen. Eleven parts of hydrogen, and eighty-nine of oxygen, form water.55. Is hydrogen found elsewhere?

It is never found but in a state of combination; united with oxygen, it exists in water; with nitrogen, in ammonia; with chlorine, in hydro-chloric acid; with fluorine, in hydro-fluoric acid; and in numerous other combinations.56. Is the gas used to illuminate our streets, hydrogen gas?

It is; but it is combined with carbon, derived from the coals from which it is made. It is therefore called carburetted hydrogen, which means hydrogen with carbon.57. How is hydrogen gas obtained from coals?

It is driven out of the coals by heat, in closed vessels, which prevent its union with oxygen.58. What becomes of the water which is formed by the burning of hydrogen in oxygen?

It passes into the air in the form of watery vapour. Frequently it condenses, and may be seen upon the walls and windows of rooms where many lights or fires are burning. Sometimes, also, portions of it become condensed in the globes of the glasses that are suspended over the jets of gas. A large volume of these gases forms only a very small volume of water.59. What becomes of the carbonic acid gas which is produced by combustion?

It is diffused in the air, which should be removed by adequate ventilation.

"I will both lay me down in peace and sleep: for thou, Lord, only, makest me dwell in safety."—Psalm iv.

60. What proportion of carbonic acid gas is dangerous to life?

Any proportion over the natural one of 1 per cent. may be regarded as injurious. But toxicologists state that five per cent. of carbonic acid gas in the atmosphere is dangerous to life.61. What are toxicologists?

Persons who study the nature and effects of poisons and their antidotes.62. Which kind of combustible used for lighting tends most to vitiate the air?

Assuming all the lights to be of the same intensity, the degree in which the substances burnt would vitiate the atmosphere may be gathered from the number of minutes each would take to exhaust a given quantity of air. This has been found to be: rape oil, 71 minutes; olive oil, 72; Russian tallow, 75; town tallow, 76; sperm oil, 76; stearic acid, 77; wax candles, 79; spermaceti candles, 83; common coal gas, 98; canal coal gas, 152. Thus it is shown that rape oil is most destructive of the atmosphere, and that coal gas is the least destructive.63. Is an escape of hydrogen gas from a gas-pipe dangerous to life?

It is dangerous, first, by inhalation. There are no less than six deaths upon record of persons who were killed by sleeping in rooms near to which there was a leakage of gas.

It is dangerous, secondly, by explosion.

In 1848, an explosion of gas occurred in Albany-street, Regent's-park, London. The gas accumulated in a shop for a very short time only. It had been escaping from a crack in the meter for about one hour and twenty minutes. The area of the room was about 1,620 cubic feet. When the gas exploded, it blew out the entire front of the premises, carried two persons through a window into an adjoining yard, and forced another person on to the pavement on the opposite side of the street, where she was killed. The effect of the explosion was felt for more than a quarter of a mile on each side of the house, and most of the windows in the neighbourhood were shattered. The iron railings over the area of the house directly opposite were snapped asunder; and a part of the roof, and the back windows of another house, were carried to a distance of from 200 to 300 yards. The pavement was torn up for a considerable length, and the damage done to 103 houses was afterwards reported to amount to £20,000. Other serious explosions have taken place. The explosions of "coal damp," which frequently occur in mines, are of a similar character.

"O Lord, our Lord, how excellent is thy name in all the earth! who hast set thy glory above the heavens."—Psalm viii.

64. What proportion of hydrogen gas with atmospheric air will explode?

According to the researches of Sir Humphrey Davy, seven or eight parts of air, to one of gas, produce the greatest explosive effect; while larger proportions of gas are less dangerous. A mixture of equal parts of gas and air will burn, but it will not explode. The same is the case with a mixture of two of air, or three of air, and one of gas; but four of air and one of gas begin to be explosive, and the explosive tendency increases up to seven or eight of air and one of gas, after which the increased proportion of gas diminishes the force of the explosion.65. What is the best method of preventing the explosion of gas?

Observe the rule, never to approach a supposed leakage with a light. Fortunately the gas, which threatens our lives, warns us of the danger by its pungent smell. The first thing to be done is to open windows and doors, and to ventilate the apartment. Then turn the gas off at the main, and wait a short time until the accumulated gas has been dispersed.66. Does hydrogen gas rise or fall when it escapes?

Being twelve times lighter than common air it rises, and therefore it would be better for ventilation to open the window at the top than at the bottom. But all gases exhibit a strong tendency to diffuse themselves, and therefore they do not rise or fall in the degree that might be anticipated.67. What proportion of hydrogen in the air is dangerous to life, if inhaled?

One-fiftieth part has been found to have a serious effect upon animals. The effects it produces upon the human system are those of depression, headache, sickness, and general prostration of the vital powers. It is therefore advisable to observe precautions in the use of gas.

"From the place of his habitation he looketh upon all the inhabitants of the earth."—Psalm xxxiii.

68. What proportion of gas in the air may be recognised by the smell?

By persons of acute powers of smelling it may be recognised when there is one part of gas in five hundred parts of atmospheric air; but it becomes very perceptible when it forms one part in a hundred and fifty. Warning is, therefore, given to us long before the point of danger arrives.69. What other sources of hydrogen are there in our dwellings?

It arises from the decomposition of animal and vegetable substances, containing sulphur and hydrogen. These give off a gas called sulphuretted hydrogen, from which the fÆtid effluviam of drains and water-closets chiefly arise. We should, therefore, take every precaution to secure effective drainage, and to keep drain-traps in proper order.70. May the use of gas for purposes of illumination be considered highly dangerous?

Not if it is intelligently managed. The appliances for the regulation of gas are so very simple and perfect, that accidents seldom arise except from neglect. In England 6,000,000 tons of coal are usually consumed in the manufacture of gas, producing 60,000,000,000 cubic feet of gas. And yet accidents are of very uncommon occurrence.