THE furnace herewith described was made out of three fire-clay bricks, two three-fourths inch arc-light carbons, a piece of large rubber tubing, a short length of hoop iron, and a bolt. In less than two hours from the time the materials were collected, the apparatus was in good running order. Fig. I.-The furnace dismantled. (The Editor of the Home Laboratory will he glad to receive any suggestions for this department and will pay for them, promptly, if available.) Fig. 1 shows the various parts before assembling. Two of the bricks have one edge beveled as shown, by means of light blows of a hammer and <!Old chisel, so that when placed face to face, with the latter edges adjacent, a V-shaped tl'ough is formed. This trough sh'Ould be of such size that, when the carbons are laid in it, the third brick, which forms the cover, will rest flatly on the sides of the other two. The carbons should fit cJ.O!sely, but not tightly, the cover brick holding them in place. A shallow groove ie, cut in one of the basal bricks, at 'right angles to the trough, leading tO the exterior of the furnace. This affol'ds a means of examining the interior during the combustion. A piece of hoop iron, or band iron, is bent so as to form a rectangle which fits the base of the furnace (Josely. Holes are punched in the ends of the iron and a bolt passing through these affords a means of tightening this binding device. If more convenient, the two bricks may be bound together with heavy iron wire. The furnace as assembled is shown in Fig. 2. The carbons should be ()opper plated and have the connections soldel'ed to them, although unplated ones may be used. A short piece of heavy rubber tubing is slipped over the end of each carbon to form an insulating handle, by means of which it may be adjusted with safety. If so desired, a small piece of IYlica bent at right angles may be used to cover the side opening of the furnace. A delivery tube may be inserted in this aperture, and the volatile products of Fig. 2.-The assembled furnace. the combustion withdrawn by aSlpiration, for the purpose of their study. Fig. 3 shows the furnace in cperation, a spectroscope being used in connection with it, as a means of investigating the chemical changes taking place. It may be found necessary to use a resistance in ()onnection with the instrument. An unplated arc-light carbon makes a very good and cheap one. Such a resistance is shown in Fig. 2, resting on the sheet of paper at uhe foot of the fllrnace. Double brass clipoS, such as are used in photography tO hang prints and film 8 to dry, make very good SUbstitutes for binding P-\sts in this, as well as in other electrkal work. 'h;.; (, nrrent which is used in the original of this skeleh is 104 volts, 15 amperes, alternating. 'ile (Jhief merits Qf the above design are its adapta- bility, cheapness, ease of construction, and the facility with whieh it may be cleaned and repaired. Fire bricks can be obtained at almost any furnace room. The capacity of this furnace is small, but the reactions are characteristic. Moreover, it may be used either as an arc or as a resistance furnace. For special operations, it may easily be made air tight with a little thick fire-clay, or ord.jnary clay mortar. The latter Fig. a.-Furnace with spectroscope attached. may also be used to repair defects which may develop with continued use. Calcium carbide, 1. typical high temperature product, may be made by finely pulverizing three parts by weight of unslaked lime, together with two parts of coal, and subjecting this mixture for an hour to the RcUon of the arc. Many other interesting processe8 may be imitated on a small scale, and research work carried on with a high degree of satisfaction.
This article was originally published with the title "Simple Electric Furnace"