Let each sheet be 1-1/2 inches wide and 5-1/2 inches thick. One-half inch from the upper ends of the two outside plates (B, B) bore bolt holes (C), each of these holes being a quarter of an inch from the edge of the plate. The inside plate (A) has two large holes (D) corresponding with the small holes (C) in the outside plates. At the upper end of this plate form a wing (E), 1/2 inch wide and 1/2 inch long, provided with a small hole for a bolt. Next cut out two hard-rubber blocks (F), each 1-1/2 inches long, 1 inch wide and 3/8 inch thick, and then bore a hole (G) through each, corresponding with the small holes (C) in the plates (B). The machine is now ready to be assembled. If the inner plate is 1/8 inch thick and the outer plates each 1/16 inch thick, use two small eighth-inch bolts 1-1/4 inches long, and clamp together the three plates with these bolts. One of the bolts may be used to attach thereto one of the electric wires (H), and the other wire (I) is attached by a bolt to the wing (E). [Illustration: _Figs. 92-95._ DETAILS OF PORTABLE PURIFIER] Such a device will answer for a 110-volt circuit, in ordinary water. Now fill a glass nearly full of water, and stand the purifier in the glass. Within a few minutes the action of electrolysis will be apparent by the formation of numerous bubbles on the plates, followed by the decomposition of the organic matter in the water. At first the flocculent decomposed matter will rise to the surface of the water, but before many minutes it will settle to the bottom of the glass and leave clear water above. PURIFICATION AND SEPARATION OF METALS.--This electrolytic action is utilized in metallurgy for the purpose of producing pure metals, but it is more largely used to separate copper from its base. In order to utilize a current for this purpose, a high ampere flow and low voltage are required. The sheets of copper, containing all of its impurities, are placed within a tank, parallel with a thin copper sheet. The impure sheet is connected with the positive pole of an electroplating dynamo, and the thin sheet of copper is connected with the negative pole. The electrolyte in the tank is a solution of sulphate of copper. The action of the current will cause the pure copper in the impure sheet to disintegrate and it is then carried over and deposited upon the thin sheet, this action continuing until the impure sheet is entirely eaten away. All the impurities which were in the sheet fall to the bottom of the tank. Other metals are treated in the same way, and this treatment has a very wide range of usefulness. ELECTROPLATING.--The next feature to be considered in electrolysis is a most interesting and useful one, because a cheap or inferior metal may be coated by a more expensive metal. Silver and nickel plating are brought about by this action of a current passing through metals, which are immersed in an electrolyte.