page_title: Pulvermacher's chain
section_title: Construction
hierarchical_section_title: Pulvermacher's chain / Construction
caption_attribution_description: A Pulvermacher chain link. The copper and zinc wires are linked to adjacent chains through the hooks and eyes at the ends.
context_page_description: The Pulvermacher chain, or in full as it was sold the Pulvermacher hydro-electric chain, was a type of voltaic battery sold in the second half of the 19th century for medical applications. Its chief market was amongst the numerous quack practitioners who were taking advantage of the popularity of the relatively new treatment of electrotherapy, or "electrification" as it was then known. Its unique selling point was its construction of numerous linked cells, rendering it mechanically flexible. A variant intended to be worn wrapped on part of the body for long periods was known as Pulvermacher's galvanic chain or electric belt.
  The Pulvermacher Company attracted a great deal of antagonism from the medical community due to their use of the names of well-known physicians in their advertising without permission. The nature of their business; in selling to charlatans and promoting quack practices also made them unpopular with the medical community. Despite this, the Pulvermacher chain was widely reported as a useful source of electricity for medical and scientific purposes, even amongst the most vocal critics of the Pulvermacher Company.
context_section_description: Electrically, the machine worked like a voltaic pile, but was constructed completely differently.  The electrodes were copper for the cathode and zinc for the anode, with the electrolyte consisting of vinegar or some other weak acid, or a salt solution.
  Each cell consisted of a wooden dowel with a bifilar winding of copper and zinc wires.  The dowels were helically grooved like a screw thread to locate the wires precisely in position.  This enabled the copper and zinc wires to be placed very close to each other without coming into electrical contact.  Insulated wires could not be used as this would interfere with the operation of the electrolyte.  Copper wires were inserted into the ends of the dowels to which the copper and zinc windings were soldered.  These end wires were either attached to, or formed into, hooks and eyes for attaching to other cells.  This arrangement is depicted in figure 2.  These attachments provided the electrical connections as well as the mechanical linkages.
  Each cell was connected to the next with the copper winding of one being connected to the zinc winding of the next and so on.  The cells could be connected end-to-end, or for a more compact assembly side-by-side, in the manner of links in a chain.  The voltage delivered by the assembly was controlled by the number of links thus incorporated and could become quite high, even though the current available was no more than from a single cell (to increase the current, the size of the cells must be increased).  The shock delivered by such chains was described as "strong" for one chain of 120 links, and as "sharp" for another of 50 links.
  Prior to use, the chain was soaked in vinegar so that the electrolyte was absorbed into the wooden dowels.  The wood of which the dowels were made was chosen to be a very porous type so that the amount of electrolyte absorbed was maximised.  The chain would continue to produce a voltage until the dowels dried out, then the chain would have to be resoaked.  Typically, the chain would be charged by slowly drawing it through a bowl of vinegar as shown in figure 4.
  A special link could be included in the chain which incorporated an interrupter circuit.  The purpose of the interrupter is to rapidly connect and disconnect the circuit so that the normally steady current of the battery is turned into a rapidly varying current.  The usual practice in the use of medical electrical batteries was to feed the output of the interrupter to an induction coil in order to increase the voltage applied to the patient by transformer action.  In Pulvermacher's patent however, there is no mention of using induction coils - the Pulvermacher battery could produce large voltages merely by adding more links to the chain.  However, the interrupter still had an effect in that an interrupted current produces a stronger sensation of electric shock in the patient than a steady current.  A novel feature of Pulvermacher's interrupter was that it was operated by the action of a vibrating spring kept in motion by the movements of the patient without the need for any external input.  Interrupters of the time typically had to be hand-cranked by the physician, although there were already some in existence using electro-mechanical automatic interrupters.  Later versions of the Pulvermacher chain used clockwork driven interrupters whose rate of interruption could be adjusted so that the rate of shock to the patient could be controlled.  Such a clockwork interrupter is fitted to the chain shown in figure 1.  It is wound up by turning the handle at the left end.
  By 1869 a variant of this chain had appeared.  In this the wooden dowels were dispensed with, and instead a hollow tube of zinc or magnesium was used.  The zinc tube itself formed the anode of the cell, and over this was wound the copper wire cathode, or in yet another version, rings of copper plates.  The zinc tube and copper wire were kept apart by stitches of thread.  Magnesium was not commonly used by battery manufacturers of the time due to its very high price (unlike today) compared to zinc
caption: Fig. 2. Cells of the chain showing details of the method of linking them together.
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