Experiment 12

Let water boil gently. Note temperature. Let it boil rapidly. Note temperature. Does water get hotter than its boiling point in an ordinary kettle? What becomes of the excess heat? What important point in the economy of fuel in cooking does this emphasize ?

Experiment 13

A. Put equal amounts of water in two beakers of the same size. Let the water in one beaker boil gently for about five minutes; in the other let it boil rapidly. Compare the rate of evaporation of the water in the two beakers.

B. Put equal amounts of water in two vessels of equal capacity, having one vessel shallow and broad and the other deep and narrow. Boil the water in them for an equal length of time and compare the rate of evaporation in the two vessels. Does the shape of the pan used and the rapidity of boiling have any bearing on practical cookery ?

Experiment 14

Mix \ cup of sugar and 1/2 cup of water; boil and note temperature, with confectioner's or laboratory thermometer; compare boiling point of the mixture with that of boiling water. Continue the boiling, noting any change of temperature.

Stages in Sugar Boiling:

Soft Ball

At 237° F. drop some of the sugar mixture into ice water. Form it into a ball between the thumb and finger, keeping under the water.

Hard Ball

At 256° F. drop some of the mixture into ice water. Form it into a ball and compare with the soft ball.

Soft Crack

At 290° F. drop some of mixture into ice water. This cracks, but if put between the teeth, will stick.

Hard Crack

At 310° F. drop some of mixture into ice water. This cracks, but does not stick to the teeth.

Continue boiling the syrup until it is a light brown color, or caramel. Pour into a tin pan and let cool.

Under what condition does the boiling point of a liquid vary? Explain the value of a thermometer in candy making.

Boiling Point

The boiling point of water at sea level is 212° Fahrenheit or 100° centigrade. The boiling points of liquids vary both with their composition and with the atmospheric pressure. It is necessary for water to overcome the atmospheric pressure before it can be changed to steam. If the altitude increases, as in ascending a mountain, the atmospheric pressure is lessened, hence less heat is required to overcome it, and water boils at a lower temperature. The boiling point of water is decreased 1° F. for each increase of 479 feet in altitude. What is the temperature of boiling water on Mt. Blanc?