APPARATUS FOR LECTURE DEMONSTRATION OF OPTICAL ACTIVITY CARL R. NOLLER Stanford University, Stanford, California
B ~ c a u s Ethe ordinary polarimeter is not suitable for demonstrating optical activity to a large class, an apparatus has been designed to be used as an attachment for a Deliueascope. The working portion of the apparatus consists of four parts: (1) a base plate of brass having a central hole and a semicircle of fine holes spaced 5' apart, as illustrated in Figure 1; (2) a Bakelite plate having a flanged circular hole; (3) an aluminum disc flanged on the outer edge to correspond with the flange on the Bakelite plate and having a circular hole, a recessed ring concentric with the hole to hold a Polaroid disc, and a semicircular slot symmetrical with the fine holes in the brass base plate; (4) a brass ring which when screwed to the aluminum disc will form a groove that will permit the aluminum disc to be rotated on the Bakelite plate. Two of the screws holding the brass ring to the aluminum disc are short posts to be held when rotating the disc. The parts are assembled as shown in Figure 2. The ends of the semicircular slot are rounded so that when the slot does not expose the semicircle of fine holes in the brass plate, light still will be able to pass through the two terminal holes of the semicircle. A thin spur extends across the slot a t the midpoint to hold the Polaroid disc in place. Adjuncts to the apparatus are a Polaroid disc, a 4-in. square of Polaroid, a 2-in. square of Corning No. 2404 H R Red Filter with polished surfaces, and a cell illustrated in Figure 3. The cell is made of brass tubing. A flange shaped to rest on the rim of the Polaroid disc 14-
