A Carbon Electric Water Heater
The water heater illustrated is for use on a 110-volt circuit without added resistance. It consists of two electrodes which are immersed directly in the water; and while it is not as artistic as the usual nickelplated heater, it is usually more economical and has the distinct advantage that it cannot be burnt out. It may be made as rapid in action as desired, is inexpensive and very convenient where water is required for experimental or industrial purposes.
For the electrodes, procure two ¹⁄₂-in. uncoppered carbons, and drill a hole in the top of each of these so that feed wires can be attached. The handle is shaped from a piece of hard wood. The lower end is hollowed out half round at either side, so that the carbons will fit in snugly. Four small holes are then drilled through from side to side for binding wires, and a large hole is made in the center for the feed wires. Two smaller branch holes are then drilled to join the center hole, so that the double feed cord may be branched out to reach both electrodes. The outer edge of the handle is neatly rounded off and boiled in paraffin so as to render it impervious to moisture.
Remove sufficient insulation from the feed cord to make a good connection with the carbons. Fish the wire through the handle from the upper end. Pull each of the two ends pretty well through, so that they can be securely threaded into the holes previously made in the carbons. Have the latter quite hot and run in as much solder as possible, forcing it in with the end of a match as it becomes plastic. Remove all traces of the flux, and paint the connection with some melted pitch, taken from the top of a discarded dry cell. The feed cord may then be pulled up tightly, which will draw the carbons in place. They are then bound by threading through several strands of copper wire. If the holes in the wood are slightly countersunk, and two small grooves filed around each carbon at the right places to let the holding wires in, the binding feature may be disposed of very neatly.
In some localities the water is so free from all mineral salts that it will not carry the current freely, which means that the electrodes must be placed closer together, or else a small pinch of common salt may be added to the water. Although, in sterilizing instruments, boiling eggs, or something of that sort, this would be of no advantage, the salt greatly hastens the boiling.