Foods and home making

Why is salt mixed with ice in freezing mixtures? This question can be answered after trying the following : Experiment 36: To show what salt does to ice ( Class Experiment). (a) Put a piece of ice in a canvas or burlap bag. With a wooden mallet, crush the ice. Measure 2 cups of the crushed ice. Put 1 cup of ice into each of 2 bowls. To one bowl add 2 tablespoons rock salt and mix thoroughly. Insert a thermometer into the center of the ice in 566 Hospitality each bowl. After a few minutes note the temperature of the contents of each bowl. Which is the colder? ( b ) Has the ice in one bowl melted more than in the other bowl? Besides lowering the temperature, what does the salt do to the ice? This experiment shows you that it is better to use a mixture of ice and salt rather than ice alone because it becomes colder. The experiment shows also that when salt is mixed with ice, the ice melts more quickly than when there is no salt. One might ask : Why add the salt when it makes the ice melt faster ? An explanation is needed to answer this ques- tion. It takes heat to melt ice. As ice melts, heat is taken from the thing in contact with Figure 148. Parts of an Ice-Cream Freezer jj. Since the can of '• Bucket' usual‘y made °f wood- the freezer is in con- 2. Metal can for holding the mixture to be .... . frozen tact with the ice, the 3. Ice and salt mixture. ice, in melting, draws 4. Dasher which beats the mixture while it heat from the can. is freezing. The can gets very cold. 5. Crank by which dasher is turned. The co)d can in turn cools the mixture on its inner side. Finally the dessert is frozen. Thus we see that the ice must melt in order to cool the mixture inside the can so that it will freeze. When ice outside the can melts, freezing inside the can takes place. How shall the freezer and ice mixture be made ready for freezing ? The can of the freezer must be clean. It must not Frozen Desserts 567 merely look clean. It must be free from odors and bacteria. The seams in a can make good lodging places for bacteria. To make sure the can is freed of bacteria, pour boiling water into the can, just before using. If the freezer is of the crank type, the dasher as well as the can needs scalding. Place the dasher inside the can before scalding. Cover the can. Let the boiling water stand in the can for a few minutes. Pour out the water. Let the can stand uncovered to cool. Adjust the can carefully in the bucket. Put the dasher in place. Pour the mixture to be frozen into the can. Cover the can and adjust the crank. While the can is being scalded or is cooling, the ice should be prepared. Place a piece of ice in a strong bag. Crush the ice by pounding it with a wooden mallet. Measure it with a dipper or a saucepan. Measure one eighth as much salt as ice. Use rock salt. Add the salt to the ice and mix thoroughly. Pour the ice and salt around the can of the freezer. Use enough of the ice mixture so that it comes as high around the can as the level of the mixture.