Imagens da página
PDF
ePub

quite as much as of the fuel which feeds it. It may be as well to mention here some of the well-known facts connected with the combustion of fuel.

The fuels commonly used are composed, principally, of carbon and hydrogen in about the following proportions:

Name. Carbon Hydrogen. Ashes, &c. Water.

[blocks in formation]

Now, combustion consists in the union of oxygen gas with the elements carbon and hydrogen, and the result is a development of light and heat, and the formation of carbonic acid and water, the carbon of the fuel uniting with the oxygen of the air to form carbonic acid, and the hydrogen doing the same to form water.

Carbon exists in its pure and crystallized form as the diamond, and this beautiful gem is combustible in oxygen gas, burning entirely to carbonic acid. This experiment

has been tried, however, only in the laboratory.

One pound of carbon requires for its combustion 158 cubic ft. of air, while the same weight of hydrogen requires 473 cubic feet. From these facts it will be seen that the different fuels mentioned above will take for their proper combustion the following minimum quantities of air, viz. :—

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small]

There is a certain quantity of oxygen in coal, wood, and peat, which somewhat reduces the amount of atmospheric air required by these fuels.

From the above tables-for which I am indebted to the researches of Péclet, Playfair, Regnault, and others, and which assume the temperature of the air to be 26 deg. F.—it will be seen that the ordinary fire plays no unimportant part in the consumption of air; for, if we assume one pound of coal per hour as the quantity required, then 148 cubic ft. of air will be con

sumed in that period, or 2.46 ft. per minute, or 2,072 cubic ft. per day of 14 hours.

These, as I have said, are minimum quantities. In practice, at least double must be allowed, as a large percentage will escape unconsumed.

In the case of the common fire, the products of combustion do not certainly escape into the room, but the air to supply the fire is required all the same, and I feel sure that not in one house in a hundred is this supply ever thought of, but is left to chance, and the cracks in the doors and windows from which drafts whistle across the room in every direction.

The second cause (B)-artificial light-requires far more serious consideration than the fire, for, commonly, the products of combustion are passed directly into the room, and are breathed in a diluted form by the persons in it.

The introduction of coal gas has been most pernicious in this respect, for few houses are built with any regard to the method of lighting, nor are the ways in

which the gas is generally burnt calculated for anything but to do the greatest amount of injury to the persons using it. Some forms of gas-light, such as the sun burners and the ventilating globe light, are comparatively free from defect in these respects, but I have never seen the latter used save in one or two private houses, and the former are almost entirely confined to offices and public buildings.

I have experienced some difficulty in obtaining the quantity of air consumed by the ordinary bat's-wing or fish-tail burner when lighted. But taking the Argand burner using 5 ft. of gas per hour, and 45 ft. of common air in the same time, as a standard, and knowing that the common burners burn from 2 to 6 ft. per hour, according to size and pressure, I think I shall be safe in calculating the average consumption of gas by the common burners at 4 cubic ft. per hour, and the amount of air at 36 cubic ft. per hour.

Now a room 25 ft. long by 16 ft. broad, and 10 ft. 6 in. high, will contain 4,200 cubic ft. of air, but a deduction must be made for

furniture, etc., of at least 10 per cent., leaving 3,780 cubic ft., or say 3,800, as the net quantity of air in the room.

Such a room will require at least three gas burners to light it, and these, as we have seen, will consume 108 cubic ft. of air per hour, rendering it absolutely unfit for breathing by depriving it of its necessary proportion of oxygen.

Ordinary candles do not vitiate more than 11 cubic ft. of air per hour, per candle.

As the chief constituents of coal gas are carbon and hydrogen, so the principal results of its combustion are carbonic acid and water. This water, in the form of vapor saturates the air of the room, which has a greater capacity for moisture when warm than when cold. This may be readily seen if, in a close warm room, we examine the windows, where the moisture will be found condensed, and perhaps running down the glass in streams.

The same effect will be produced by placing a glass bottle filled with cold water on the table, the moisture will settle thickly upon it like dew upon the grass on a clear night.

« AnteriorContinuar »