LABORATORY MANUAL CHAPTER I MANIPULATION AND FUNDAMENTAL PRINCIPLES 1. The Bunsen burner. a. The Bunsen burner is the common form of apparatus used in laboratory operations where heat is applied. It consists of the tube A (Fig. 1), screwed into the base C. The tube has two small round holes near its lower part. A band B, provided with similar holes, fits around the lower part of the tube in such a way that the holes in the tube may be closed or opened by turning the band. Gas is admitted to the burner through D by means of rubber tubing. Unscrew the tube and examine the different parts of the burner; then put them together again and light the gas by holding a lighted match 4 or 5 cm. above the tube and turning on the gas. The gas should be adjusted so as to give a flame about 10 cm. high. The gas entering the burner mixes with air drawn in through the holes in the lower part of the tube and burns with an almost nonluminous flame. If the band is adjusted so as to close the openings, the flame becomes luminous. Always use the nonluminous flame unless otherwise directed. B FIG. 1 b. Hold an iron wire in various parts of the flame to gain an idea as to the relative temperatures. Pass a piece of glazed paper transversely through the flame, holding it steady for an instant across the flame. What information do you get from the way in which the paper is scorched? Pass a piece of paper edgewise through the axis of the flame in the same way. c. From these experiments draw a diagram of the flame, indicating the hot and the cooler regions. 2. Heating a liquid in a test tube. Hold the test tube between the thumb and fingers (Fig. 2), constantly rotating it backward and forward so as to apply the heat uniformly. The heat should be applied to the upper portion of the liquid, care being taken, however, that the flame does not strike the tube above the level of the liquid. In case the upper part of FIG. 2 FIG. 3 FIG. 4 the tube becomes heated it may be supported by a test-tube holder (Fig. 3) or by a band of paper circling the upper part of the tube (Fig. 4). The sudden formation of vapor at the bottom of the tube sometimes causes the contents of the tube to be thrown out; hence care must be taken not to point the tube toward anyone. Half fill a test tube with water and apply heat until the water boils rapidly. 3. Pouring a liquid from one vessel to another. In this operation care must be taken to prevent the liquid from running down the side of the vessel from which it is poured. A glass rod should be held lightly against the rim of the vessel, as shown in Fig. 7. The liquid will flow down the rod. Fill a beaker with water and transfer it slowly to another |