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Posted By: J. Chris Hausler on: 03/21/2008 11:58:48 EDT
Subject: RE: researching telegraph

Message Detail:
An excellent reply Ray, however, one nit to pick. The Daniell Cell was a wet cell, not a dry cell. Dry cells didn't come along until much after the civil war and further, for most purposes dry cells make very poor telegraph batteries (in classic service) as telegraph lines in America were most all based on the "closed circuit system" which required that current flow "all the time" in the circuit which would (and does) quickly run down a dry cell (I do use dry cells sometimes in demonstrations and usually have to bring along replacements. If I can plug into the wall somewhere, however, I use Radio Shack power bricks instead as they don't run down :-) However, the Daniell cell (as well as others, Morse started using the Grove cell) is ideal for closed circuit service. Note that it was a simplification of the Daniell cell called the gravity cell which became the "standard" telegraph battery cell. As with most cells, there are two chemical compounds and two electrodes, one electrode imersed in each chemical. However, the two chemicals have to be kept from mixing but still allowed to exchange ions. This was frequently done using an unglazed porcelain cup to separate them, and this is how the Daniell cell was configured. However, someone figured out that the two chemicals used in the Daniell cell, copper sulfate and zinc sulfate could be kept separate because of their different specific gravity, the zinc sulfate would float on top of the copper sulfate. Since a little bit of mixing would occur to keep the cell working required that it be generating current most of the time, thus ideal for the closed circuit system. This simplified the Daniell cell as the porcelain cup (and the maintenance of it) was no longer required. However, of course, there was still maintenance required as in use both make ever more zinc sulfate (consuming the zinc electrode) and consume copper sulfate (making copper). Thus eventually the zinc element has to be replaced, some of the zinc sulfate siphoned off and more copper sulfate added (usually in the form of what was called "Bluestone").

J. Chris Hausler
Morse Telegraph Club
Office VE, sine CH

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