This section is from the book "Health", by W. H. Coefield.
Another thing that should be carefully remembered is that some of these mineral oils have a penetrating power, and will pass through a china lamp and appear on the outside, and evaporate into the air, causing a disagreeable smell in the room.
Many of you burn paraffin in lamps, and perhaps you have noticed that invariably when you have taken hold of them you have found oil on your fingers, and then thought that the lamp had not been properly cleaned. This is not so ; the oil has come through the pores of the substance of which the lamp is^made.
We will now consider Coal Gas. Gas may be prepared by the dry distillation of various substances, but is now exclusively made from coal The coal is placed in large vessels called retorts, and heated; various substances are given off, and something remains; this is the valuable substance we call coke, used chiefly in engines, when it is necessary not to have smoke, as coke bums without smoke.
The substances given off consist, in the first place, of a large quantity of tar, which is used for an immense variety of purposes in commerce, very largely for the preparation of carbolic acid, the well-known disinfectant ; the aniline colours, mauve, magenta, etc., are also prepared from coal tar. Further, a considerable quantity of ammonia goes off. This is collected by washing the gas with water, which absorbs the ammonia, and this ammoniacal liquor is used for the preparation of manures, and is now the great source from which ammoniacal manures are obtained. Besides these, a mixture of gases is given off which requires to be still further purified before it can be used for burning. It has sulphuretted hydrogen in it, which has a smell like that of rotten eggs, and has to be separated from the gas, and this is done either by passing it over lime, or over oxide of iron, other compounds of sulphur being partly separated at the same time. The gas is more efficiently purified by the lime process, but the mixture of waste lime and sulphur compounds is liable to cause a serious nuisance to the neighbourhood.
The remaining mixture is the gas we burn, and it consists chiefly of a gas called light carburetted hydrogen, or marsh gas, which forms carbonic acid and water when burnt in air. It contains, also, pure hydrogen gas, which has the property of burning in air, and producing water; and heavy carburetted hydrogen gas, which burns in air to form carbonic acid and water, giving an intense light. This last is the substance to which the lighting properties of coal gas are mainly due. Coal gas always contains carbonic oxide, sometimes as much as 11 or 12 per cent. It always contains compounds of sulphur, which, when burne^ in the air, produce sulphurous acid with a little sulphuric acid.
The gas we use for burning is exceedingly poisonous. It contains a sufficient percentage of carbonic oxide gas to kill any animal, and it is therefore extremely important that the gas should not be allowed to get into rooms, even in the smallest quantity. It contains one of the most poisonous substances with .which we are acquainted. It is very fortunate that the gas has a very strong and unpleasant smell, as otherwise a great many people would be poisoned by it. A very foolish thing was once done. A man took out a patent for depriving the gas we burn of its smell, but the gas companies fortunately did not adopt it.
When coal gas escapes into the air, it forms a mixture which explodes very readily when a spark is applied.
What are the dangers from breathing air into which the products of the combustion of the substances we use for lighting have been allowed to escape ?
It produces in persons who breathe it for a lengthened period what is called anaemia, or bloodlessness; and especially when the combustion is incomplete, and soot escapes into the air, it produces cough, lung complaints, and is particularly fatal to persons who are liable to consumption. It is, therefore, extremely important that the products of combustion should not be allowed to escape into the air of rooms. They should be conducted away, or, at any rate, plenty of fresh air should be admitted.
I may give you an idea of the amount of damage done to the air of rooms by candles, even where perfect combustion takes place, by telling you that two sperm candles produce as much carbonic acid, and consume as much oxygen, as one man. A man in a room with two sperm candles burning requires twice the amount of fresh air that he would if he were by himself. The same is the case with a good lamp. A cubic foot of gas destroys the oxygen of about eight cubic feet of air. A poor burner will consume at least two cubic feet in an hour, and so destroy the oxygen of sixteen cubic feet of air, that is to say, will destroy as much air as four men ; so that a man sitting in a room with a gas burner that only burns two cubic feet in an hour, requires at least five times as much change of air as he would if he were there by himself.
We now come to the substances used for warming purposes, and the apparatus. I will content myself with speaking about coal, and the apparatus in which it is burned. When burned in the ordinary fireplace it is burned at an immense disadvantage. About ninety per cent of the heat escapes up the chimney, but it has one advantage, and that is, that it changes the air of a room very quickly, as air must be supplied to the fire, or else the fire will go out. The only way by which air can enter to supply the fire, when a room is closely shut, is the chimney, and so air comes down the chimney, and that is one cause of smoky chimneys.
Now, a word or two about stoves. Stoves are made of various materials, as earthenware, wrought iron, or cast iron. Quick combustion stoves very much resemble ordinary fireplaces. In slow combustion stoves coke is generally burnt, and a limited supply of air is admitted to them by a pipe from outside, so that there is no fire to be seen in the room.
They are used for wanning large rooms which require a great deal more heat than is given by an ordinary fireplace. The disadvantage is that, when an iron stove gets hot, it dries the air of the room, and this dryness is only partially obviated by placing a vessel of water on the top of the stove. Another thing is that the air in which a stove is burning always contains carbonic oxide gas. That has been proved by a series of careful experiments. Another disadvantage is, that they always make the air of a room smelL You all know what is called the smell of cast iron. It is due to the partial charring of the organic matter in the air of the room, and the smell is worse if the air in the room is rather fouL So that stoves, even though they have a pipe to convey the results of combustion from a room, have great disadvantages, especially in small rooms.
The ordinary fireplace has been immensely improved in construction, and that known as the Galton stove, invented by Captain Galton, is a great improvement, though it has not been brought into sufficient use. There is an air chamber around the flue of this stove.
Which communicates by a pipe with the external air, so that as the fire burns in the stove, external air comes into the chamber round the flue, is warmed, and gets into the room, partly to supply the fire, and partly to supply the room. By this contrivance as much as 35 per cent of the heat is saved, and fresh air is brought into the room, and that is of very considerable importance.
The ordinary stoves do not change the air of a room sufficiently, but there are certain kinds of stoves in which either coal or gas may be burned in which there is a contrivance for bringing fresh air already warmed into the room by a pipe running through the stove. These are called calorigen stoves.