FoodNet

Handbook of domestic science and household arts for use in elementary schools

1900

Page 20

Presented as published in 1900. Historical recipes may not meet modern food-safety standards. Cook from the modern interpretation, not the original instructions.
Since as far as is known nothing in the physical world is ever destroyed, during this consumption of fuel new com- binations of the elements hydrogen and carbon with the oxygen of the air must be formed and pass off as simpler and usually invisible compounds. Smoke, which often ac- companies combustion of carbon, is not a compound, but carbon in a finely divided state — a result of deficient supply of oxygen, and hence due to lack of perfect oxidation. Products of Combustion. COo, CO, HoO. — When the union of carbon with oxygen is not restricted by a limited supply of air, the resulting product is carbon dioxid, formerly called carbonic acid gas. When the supply of air is very limited, the product formed is carbon monoxid — a very poisonous gas. It is formed in hard coal stoves whenever the air supply is restricted by closing the drafts and may be seen in a state of combustion as pale blue flame hovering over the glowing coal. Carbon monoxid is also a part of what is known as water gas. The union of the hydrogen in the fuel with the oxygen in the air produces water, which as water vapor passes with the other products of oxidation into the atmosphere. Hydrogen. — Hydrogen ignites at a much lower tempera- ture than carbon, about 300° F. The heat of the flame pro- duced is great, but there is almost no light produced. Carbon. — On the other hand, carbon when ignited glows but does not produce a true flame, at most only a blue flame, which may be due to the oxidation of carbon monoxid into carbon dioxid. When the two are burned together they produce a lumi- 36 HANDBOOK OF DOMESTIC SCIENCE nous flame, the light being due to the incandescent condition of finely divided carbon. This may be shown by holding a piece of porcelain in the flame of a candle or by sifting pow- dered lampblack or charcoal into the flame of the Bunsen burner. Hence flame to give light as well as heat must be produced by a fuel containing carbon and hydrogen. Ash. — Aside from smoke, solid fuel leaves another visible residue known as ashes or ash. Ash is composed of mineral matter taken from the soil by the vegetation during growth. It is a very poor conductor of heat, absorbing it in large quantities. Smoke has the same effect, hence their presence is detrimental if great heat is to be radiated. The effect of retention of heat by ashes may be illustrated by cooking an egg or a potato by burying it in the hot ashes. The lack of conducting power may be shown by placing cool ashes on the palm of the hand so that it will be thickly covered and then placing a live coal upon it. Essentials for Combustion. — There are three essentials for perfect combustion : — I. A supporter of combustion. II. A combustible. III. Sufficient heat to cause a union between the combus- tible and the supporter of combustion. Supporter. — The supporter of combustion is nearly always oxygen as found in the mixture air. The other constituents of air are all inert substances retarding combustion, or when present in excess preventing it. Hence the necessity of removing exhausted air and the products of combustion as soon as formed. Their deadening action is utilized in chem- ical fire engines. A larger proportion of oxygen in the air would render life very much less safe. " Spontaneous com- bustion " would then be the rule rather than the exception. Method. — Combustion.