A base of any convenient size, say, 16 x 8 inches, has fastened to one end a tripod or similar elevated support. A slab of slate 4 x 8 inches and ⅞th of an inch thick is drilled at the ends to take the bolts holding the pivot and guide posts shown.
The posts are made from ³/₁₆th inch strap iron ¾ inch wide. The pivot post being made by giving the metal strip a quarter turn with a large wrench while holding one end of the strip in a vise. The guide post is formed by slotting the end of the bent strip to pass the lever.
The lever is made from ¼ inch iron, ¾ inch wide and 20 inches long. One end is drilled to pass the bolt pivoting it to the pivot post. A saddle bent from ⅛ inch sheet iron is pivoted to the lever as shown so as to be directly over the center of the slate slab. The saddle serves to equalize the pressure at point of contact with the cell undergoing treatment and gives a direct vertical thrust.
The weight used with the press is made by pouring lead into a round form 2¼ inches in diameter and 5 inches high. Any other weight of eight pounds can be used. A hook bent from a strip of brass or iron is inserted in the lead while in a molten state and serves to hang the weight on the lever.
Fig. 9. Platen for Cell
Fig. 9. Template for Applying Selenium
A bunsen burner is utilized to heat the slate slab. Some convenient means should be employed to control the height of the flame, either a valve mounted on the base or a screw clamp on the rubber hose supplying the gas.