284. What effect has the burning of a fire upon the composition of the air?
It is found that in burning 10lb. of coal the oxygen contained in 1,551 cubic feet of air is altogether absorbed. It is therefore necessary to keep the atmosphere of a room, in which a coal fire is burning, fresh and pure, to supply 155 cubic feet of fresh air for every pound of coal that is consumed.
"O Lord how manifold are thy works, in wisdom hast thou made them all: the earth is full of thy riches."--Psalm civ.
285. Why does wood which is "green" hiss and steam when it is burnt?
Because it contains a large amount of water, which must be evaporated before combustion can proceed.
286. What is the effect of this evaporation?
A great deal of heat is unprofitably expended in driving off the water of the fuel.