A piece of brass tubing, P, 1 1/4 inches long and having an internal bore of 1/2 inch is slipped over U. A slot cut in P fits over a small pin set in U and permits P to be slid up and down but not to turn around.
Fig. 100. Electrolytic Detector.
A head in the form of a circular brass washer, E, 1/8 inch thick, 1/2 inch in diameter and having a 5/32-inch hole bored in the center is soldered in the top of the tube, P.
A circular piece of hard rubber, H, 2 inches in diameter and 1/2 inch thick is fitted with a brass bushing having a hole in the center with an 8-32 thread to screw on the rod, R.
A spiral spring is placed around R between U and the head E. A small brass washer should be placed between H and E in order to eliminate friction. When H is turned in one direction, the spring will cause P to rise, and when turned in the other direction it will be lowered.
A brass arm, A, 1/4 x 1/4 x 1 1/2 inches carries a small thumbscrew, r, at one end, while the other end is soldered to P as shown in Fig. 96. The Woolaston wire is soldered to T.
Fig. 101. Details of Electrolytic Detector.
A small carbon cup 3/4 x 3/4 inch serves to hold the electrolyte. A 3/8-inch hole is bored 1/4 inch deep in the bottom of the cup and poured full of melted lead. The lead is then bored and tapped to fit a machine screw which fastens the cup to the base. Connection is made from a binding post to the machine screw. A second binding post is connected to the screw which fits into the bottom of U and holds it to the base.