Directly in the center and 1¾ inches from the bottom of one of the 11 × 12 inch boards bore a 1½-inch hole. The remaining piece should be sawed out, leaving a hole at g. This is so that the board can be removed in case of a leak without disturbing the cleaning screw. These pieces should be fitted to their places with round head screws, and if properly done will form an acid chamber which will measure 10 × 10 × 12 inches, and the gas chamber will measure 10 × 10 × 10 inches. The acid chamber must be larger than the gas chamber, to allow the full charge of acid to be used without overflowing.
Fig. 8.—Making the Shelves and the Perforated Bottom.
Now fit the sheet lead. Six-pound is plenty heavy for this generator and will last a lifetime. Cut it as shown in Fig. 8, A and B. Form the lead so that the seams when finished will come on the outside, as in case of a leak in a seam it can then be easily repaired by removing one of the boards. The projecting edges of lead should be dressed over the edges of the top to protect the wood from the acid, but do not fasten them, as the tanks will have to be removed and the seams burned.
Now cut the piece of lead C to form the top of the gas chamber. None is needed for the acid chamber, as it must be left open so that no resistance will be offered to the action of the gas on the acid. Five inches from the side and 2 inches from the back of this piece cut a hole, d, Fig. 8, 1¼ inches in diameter, and dress it up with the bending iron to 1½ inches in diameter, taking care to preserve the thickness of the metal. This is for the acid supply pipe to pass through.
Three inches from the side and 3 inches from the front cut a ⅛-inch hole, e. This is the gas outlet. Three and one-half inches from the opposite side and 4 inches from the front cut the hole f, 2¾ inches in diameter. Dress this up and over the flange of the charging screw a, Fig. 6. This may seem a difficult thing to do, but lead must be worked slowly. Heating the lead while dressing it will help wonderfully. If it is not possible to make a good job in this manner, then cut the hole 4 inches in diameter and burn in a collar sufficiently big to dress over and cover the flange of the screw. This is to prevent acid from coming into contact with the screw and destroying it. Treat the cleaning screw in the same manner. The location of this screw is in the center and as close as possible to the bottom of the gas chamber, as shown in Fig. 8 at j.
Fig. 8½.—Showing the Perforated Spelter Shelf in Place in the Generator.
It is necessary to have a false perforated bottom in the gas chamber to rest the zinc upon and also to keep it above the solution. To make and support this bottom take a piece of sheet lead 14 inches square, as shown in Fig. 8, and form it in the shape of a pan, which will drop easily into the gas chamber k, Fig. 8½. A piece of 1½ or 2 inch lead pipe, 2 inches long, n, should be burned on the center of the false bottom, to prevent the center from sagging with the weight of zinc. Then punch the bottom O, Fig. 8, full of ¼-inch holes. A 1½-inch hole, y, should also be cut in line with the holes for the acid supply pipe.
Remove the tanks and burn the seams. Place the tanks back in place. Then take a piece of the ⅛-inch brass pipe, 1½ inches long. Cut a thread on one end, tin the other end, and burn it to the top of the gas chamber at e; also the collar for the charging screw. Then place the perforated bottom in the gas chamber, taking care to keep the holes for the acid supply pipe in line. Do not make any mistake in putting in this bottom. Its use is to act as a shelf to hold the zinc, and if put in properly it will hold the zinc about 2 inches above the real bottom. The top of the gas chamber c should then be burned in. Now by measuring find the exact length of the acid supply pipe, Fig. 7, i. This pipe should extend from the bottom of the acid chamber o to the bottom of the gas chamber p, as shown in Fig. 7. From one end of this pipe several V-shaped pieces should be cut, p, about 1 inch deep.