Electrolytic pencil

In order to pilot this process, SNPE has developed an annular ceU having a cone-shaped electrode section. The magnesium anode is placed into the conic section and fed like a pencil into a sharpener as it is consumed during electrolysis. The carbon dioxide is introduced into the electrolyte externally to the cell. 

The magnesium-based pencil sharpner electrolytic cell used is shown in Fig. 15. It has the following features ... 

Pulvermacher s chain — This was a -> battery consisting of copper and zinc wires wound around pencil-like wooden sticks, and the sticks connected in a chainlike manner. The wooden sticks were soaked with dilute acetic acid, so that the chain produced electricity also when removed from an electrolyte bath. The chain was used in galvanic therapy. 

Drill a hole in the center of the pipe cap for the bottom cap to accept a 10/24 screw. Then, center the 1" PVC cap inside the cap, and draw an outline with pencil. The 10/24 screw hole should be dead center within this outline. Drill a 3/8" hole between the inner wall of the 3" PVC cap and the circle outlined for the 1" PVC cap (see illustration at right). This /s" hole is the electrolyte entry port. Cut and epoxy the 3/8" barb connector into the hole. 

OTHER COMMENTS used for lead pencils, crucibles, stove polish, molds, lubricants, paints, and coatings other uses include electroplating, cathodes in electrolytic cells, matches, and explosives. 

Ultimately, this combination of requirements led to the pencil sharpener cell, in which the magnesium anode was a rod (diameter 40 cm) with one end shaped as the point of a pencil. The shaped part of the anode sat within a conforming, conical cathode (Pb-plated stainless steel), with the electrodes separated by a thin polymer spacer. The weight of the anode ensured that the anode pressed down on the spacer and that the shape was maintained as metal was lost from the anode. The production unit had two such cells, each with an active electrode area of 0.6 m, and was operated with a cell current of 600 A. The operating pressure was 5 bar, and electrolyte was circulated though the cell from a 400 liter reservoir. For the manufacture of fenoprofen the unit was operated in batches, whereby a batch of 60 kg chloroethyldiphenylether was dissolved in 340 kg dimethylformamide that also contained 3 kg tetrabutylammonium bromide. Each batch, when processed for 28 h, led to 50 kg of isolated fenoprofen. The good yield ( 80%) showed the electrolytic route to fenoprofen to be very competitive with more traditional syntheses. 

Technique. The origin is marked on the paper with the help of a pencil. Subsequently, the paper is placed on an insulting solid support with its ends hanging in the electrolyte (wicks can be used to establish contact). It takes about 30 minutes for the paper to equilibrate with the electrol5Te. 

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